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Znorganica Chimica Acta, 11 (1974) 47-104 0 Elsevier Sequoia S.A., Lausanne -Printed in Switzerland
Invited Review
47
Rate Parameters for Ligand Replacement Processes in Octahedral Complexes
of Metals in Oxidation State Three
J. 0. EDWARDS,* F. MONACELLI and G. ORTAGGI
Zstituto Chimico, University of Rome, Rome, Italy and
Department of Chemistry, Brown University, Providence, Rhode Island 02912, U.S.A.
Received March 13, 1974
Contents
1. 2. 3.
4. 5. 6. 7. 8. 9.
10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21.
Introduction Errors, Precision, and Accuracy Symbols and Notations A. General B. Reaction Conditions C. Abbreviations D. Rate Constants and Activation Parameters E. Experimental Methods F. Remarks and Comments Metal Oxidation State and Size Acid Hydrolysis (Aquation) Solvolysis Acid-Catalyzed Aquation Base Hydrolysis Leaving Group Effects Isomerization Ligand Isomerization Racemization Ambiguity in Site of Attack Second-Order Anations First-Order Anations Activation Volumes Summary Conclusions Acknowledgements Text References Data Tables Data Table References
1. Introduction
The reactivity of octahedral metal complexes has been the subject of a large number of experimental investigations, and the results have been reviewed
* To whom correspondence should be addressed at Depart- ment of Chemistry, Brown University, Providence, Rhode Island 02912, U.S.A.
several times. The basic problem which justifies such a wide interest is the mechanism of the ligand substitu- tion process occurring at the metal atom.
In spite of the large amount of data, there are few cases for which the detailed aspects of the reaction mechanism have been settled. Generally, the usual kinetic approach leaves considerable uncertainty as to the structure of the transition state. In this respect, substitution reactions of octahedral metal complexes are not amenable, as yet, to as ready an analysis as are the nucleophilic displacements on saturated carbon substrates or as are the ligand replacements on ds square planar metal complexes.
The most widely used approach to the problem is a comparative analysis of the behavior shown by a suit- ably selected class of compounds. In practice, this “be- havior” is represented by the rate constants measured at a common temperature when the compounds are varied in such a way as to explore the rate changes due to variation of a given structural parameter such as leaving group, chelation, steric hindrance, etc.
However, rate constants, being related to the free energy change of the activation process, may be divided into the enthalpic and entropic contributions. Thus, at least in principle, the knowledge of both dH* and d S” (while equivalent as a whole to the corresponding rate constants) is more advantageous. These para- meters and the activation volume dV* give useful information on different, although to some extent re- lated, aspects of the reaction mechanism. We stress the fact that small but detectable differences in rate constants may not be ready for analysis as they presum- ably are related to minor changes in mechanism. Also we are aware of the condition that identical rate con- stants at one given temperature may belong in differ- ently reacting systems as a consequence of the com- pensation of enthalpy terms with entropy terms.
There have been, unfortunately, many workers who did not attempt to evaluate activation enthalpies, and even more who neglected to calculate the activation
48 J. 0. Edwards, F. Monacelli and G. Ortaggi
TABLE I. Mechanistic Classifications of Langford and Gray.
There are three categories of stoichiometric mechanisms distinguished operationally by kinetic tests.
1. Dissociative (D): intermediate of reduced coordination number, which may be detected by its selective reactivity.
2. Associative (A): intermediate of increased coordination number, which may be detected by departure of the rate ex- pression from strict second+rder kinetics when the reaction is followed in the direction for which the transition state lies after the intermediate.
3. Interchange (I): no kinetically detectable intermediates. There are two major categories of intimate mechanism that may be distinguished operationally if it can be assumed that a group of reactions with related mechanism can be identified.
1. Associative activation (a): the reaction rate is approxi- mately as sensitive (or more sensitive) to variation of the entering group as to variation of the leaving group.
2. Dissociative activation (d): the reaction rate is much more sensitive to variation of the leaving group than to varia- tion of the entering group.
D mechanisms must be dissociative. A mechanisms must be associative. Therefore, we adopt the following as the simplest combined notations designating both stoichiometric and intimate mechanism: A, I,, Id, D.
entropies. One reason for the deliberate omission is that, while it is relatively easy to distinguish among rate constants differing by more than 10% by con- ventional kinetic techniques, the experimentally-based activation enthalpies are less discriminating. Suffice it to say here that, in spite of the lower degree of ac- curacy for the activation parameters, the value of dS* for the base hydrolysis mechanism provided a clear decision between the proposed alternatives that were so long and so unnecessarily debated in the in- organic mechanism literature.
In this review we have collected rate constants plus activation parameters for the ligand substitution and isomerization reactions of metal complexes with the metal always in the oxidation state +3. This choice has been suggested both by the fact that much of the available data concern this class of complexes and be- cause the rates cover a large range encompassing both labile and inert species.
The data reported here are those that appeared in the literature through 1971 and in some cases those that appeared in 1972 and 1973 in the most common periodicals. We have tried to be reasonably complete, however certainly we have missed some relevant arti- cles and we apologize for our incompleteness to the authors of such articles.
Throughout the review the terminology introduced by Langford and Gray’ will be adopted. Their inter- change mechanism - either dissociative (Id) or asso- ciative (Ia) - is in our opinion suitable for our pur- poses being sufficiently flexible to cover most of the cases discussed herein. The definitions on which this
terminology is based are given in Table I. Further details about their description may be found in their text.’
We feel that the numbers collected here will provide a basis for discussion and speculation to chemists interested in this research area. It is not our purpose to attempt a complete analysis of the data; rather we shall present possible approaches to such an analysis. Also we shall probe somewhat more deeply into some specific cases, which, at the moment, appear to be sufficiently clear to us to warrant detailed discussion.
The mechanisms for ligand replacement reactions in octahedral complexes have been discussed often and elsewhere. The background plus many details in this field of research are presented in published books and reviews.l-14
2. Errors, Precision, and Accuracy
It is possible in certain instances to compare rate data on the same reaction as measured by several investi- gators. Taking as example the reaction
Cr(NH3)5ClL+ + H,O+ Cr(NH3&H203+ + Ct
we have found eight articles giving relevant numbers. These numbers are presented in Table II.
Ignoring for the moment the fact that the media are not identical, it can be seen that the variation in rate constants is about a factor of two. This represents a difference of 0.41 kcal moT’ in the free energy of activation. It is immediately apparent that the values of dH* are much more divergent, with the lowest reported value being 20.7 kcal mar’ and the highest being 23.6. Since an energy change of 1.36 kcal mol-’ represents a change of one power of ten in rate - all other things being equal - the variability in dH* shows that the change in rate constant with tempera- ture is less well known than the rate constant itself,
TABLE II. Hydrolysis of Chloropentaamminechromium(II1) Cation.
iu k(25’ C) dH* AS+ Ref.d
0.106 6.8 x 10d 20.7 _= 6.0 x lOA 21.5 _h 6.0 x lo4 21.6 _ 8.0 x 10” 21.8 0.1 9.3 x lo+ 21.8 0.5 6.8 x lo+ 22.2 1.0 3.9 x 10” 22.3 0.2’ 5.6 x 10” 22.4 1.0 7.4 x 10” 23.6
-12.7 34 -10.3 45 -10.0 45 - 8.7 %40 - 8.4 41 - 8. 43 - 8.5 42 - 7.5 44 - 2.8 37
a MeOH-H20 mixture. b EtOH-HZ0 mixture. ’ DzO. d These reference numbers refer to that list which is entitled Data Table References.
Ligand Replacements in Octahedral Complexes 49
provided of course that the differences appear to result from both random fluctuations and genuine variations. Separation into these two causes of dif- ferences is not yet possible. From the data of Table II, one can see the compensation of d H” and d S* often ascribed to errors but the rate constants show some divergences that we believe are genuine. The variation in dH* values usually leads to a related variation in dS* values. In this case a variation of 4.58 cal mar’ deg-’ is equivalent to a change of one power of ten in the rate constant.
Although it is not our primary concern here, the interrelationship between dH* and dS* is of suf- ficient importance to our discussions of mechanism that some mention be made here. More broad discus- sions of this “compensation effect” are to be found elsewhere.”
There arc a number of different reasons because of which the activation parameters may not be completely reliable quantities; fortunately most of these reasons are easily recognized and can possibly be avoided. For a given reaction, both the entropy and the enthalpy of activation may be obtained from the ln(K/T) versus l/T Eyring plot. The slope of the plot is equal to dH* /R, while the intercept is related to the entropy through the equation
AS* = {Intercept-ln(K/h)}R
where K, h and R are the Boltzmann, the Planck and the ideal gas constants, and T is the absolute tempera- ture, respectively.
The maximum error in ln(K/T) is the sum of the relative errors for both k and T. The latter is usually measured to within fO.l o C in the temperature range from 0” to 100” C where by far most of the kinetic runs have been carried out. This comes out to be a sufficient degree of accuracy in temperature since the relative error dT/T is not larger than 0.0003, thus negligible compared to the relative error in k (4 k/k) which is about 0.05, generally. Thus it may be assumed that
d ln(k/T) = d In k = d k/k = 0.05
A point which deserves more attention is the width of the temperature range which should be employed in order to obtain activation parameters of sufficient
Figure 1. A modified Eyring plot showing the variation of the activation parameters (slope gives AH* and intercept gives AS*) due to the experimental errors.
accuracy. It is obvious that the smaller is the difference between the highest and lowest temperatures studied, the higher is the uncertainty in both slope and inter- cept of the Eyring plot.
Using an empirical basis, let us assume that the un- certainty of the slope of an Eyring plot @AH* /R) as in Figure 1 be one-half of the difference of the slopes of the lines passing through points A and B, and C and D, respectively. It can be shown that dd H* /R is given by the formula
ddH*lR = 24 k TITz k(T,-T, + 24 T)
neglecting dT(T,-T1) compared to T2T1. Most com- monly, the temperature range employed in the kinetic studies of the reactions has a width of 20 degrees. This width plus a +O.l”C error in temperature measure- ment does not justify an accuracy better than +0.5 kcal mar’ for dH* or better than +2.0 cal moT* deg-’ fords*.
Thus if there are no experimental reasons (for instance, analytical limitations) to constrain the study of the temperature effect to such a narrow range, this range should not be less than 30” C.
Another important reason for adopting a wider temperature range is the need for a check of linearity in the Eyring plot. The case of a system reacting by two (or more) different parallel kinetic patterns of the same kinetic order is not infrequent. If the two paths have different activation parameters and if more than two points are obtained, the resultant Eyring plot will show curvature. The curvature may only become ap- parent over a significant temperature range.
Often a critical step in the calculation of dH* in- volves the placement of the straight line which appears, just by inspection, to fit the experimental points of the Eyring (or Arrhenius) plot. It should be recognized that this procedure, although time saving, can seriously decrease the degree of accuracy of the activation parameters. This “subjective effect” may be larger than it is usually believed. One of us (J.O.E.) has had the occasion to test on a statistical basis the degree of uncertainty introduced by a subjective graphical me- thod in the evaluation of activation energies. A set of experimentally derived rate constants and tempera- tures was given to a class of students of chemical kinetics as homework. Each of the students was asked to calculate the activation parameters at 600” by the usual graphical method. The data obtained from the students are presented in Figure 2-I which is a plot of E, (to the closest value of fO.l kcal mar’) against dS* (to the closest +O.l cal mar’ deg-‘). Each circle represents the answer of one (0) two (-0) or three (-C-) students. The calculated enthalpies and entropies are linearly correlated as is to be expected when a subjective error in drawing the slope of the
50 J. 0. Edwards, F. Monacelli and G. Ortaggi
-12 I----=- -8 4 0 4 8 12 16 20 tant plot of E, (or dH* ) against AS* should be equal, of course, to the temperature chosen for the calculation; the chosen temperature was 600” and the value of the slope turns out to be 607’.
122 -2’3 -24 -20 -16
AS*
Figure 2. Four plots of AH* (or E,) versus AS* for cases where there appears to be variability in activation parameter determination. Line I refers to the student data mentioned on page 11; lines II, III and IV refer to hydrolysis data for trans- Co(en)&$+, Cr(NH3)5ClZf and Co(NHJ)&12+ respectively
Arrhenius plot is made. The error in the slope then introduces an error in the calculation of dH* , even when the rate constant used (and thus the d G* value used) is the same in every case. The slope of the resul-
Suffice it to say here that mathematical procedures such as least squares are to be preferred to more sub- jective procedures such as “eye-balling” the slope.
Data presented in Tables II and III concerning the aquation of the inert complexes Cr(NH3)5C12+, CO(NH~)~C~~+ and trans -Co(en),C12+ offer some striking examples of the consequences of a “subjec- tive linearization” of the Eyring and Arrhenius plots. These reactions have been studied by different workers under different conditions and by different techniques. While the rate constants are reasonably close to each other,* the activation enthalpies for the chloropenta- amminechromium(II1) and the chloropentaammine- cobalt(II1) cations span a 3 kcal marl range, and the
* As mentioned later, some of the rate constants listed were obtained by extrapolation to 25°C from data at different temperatures by using the AH* value calculated by each author. Thus, in some cases, at least in part, the differences in values of k reflect the differences in values of AH*
TABLE III. Activation Parameters and Reaction Conditions for Aquation of the Complexes Co(NH3)&lzf and trans-
-
Complex Reaction Conds.
_
0.1 M HNOZ Hz0 Hz0 0.1 M (K,H)CI~~ 0.002-1.0 (Na,H)N03 EtOH, Hz0 (30% w) DXN, H,O (30% w) ETG, Hz0 (30% w) 0.1 M HNOZ H20 H20, MeOH (20% w) MeOH, Hz0 (39% w) MeOH, Hz0 (60% w) EtOH, Hz0 (18% w) EtOH, Hz0 (36% w) EtOH, Hz0 (54% w) Acetone, Hz0 (20% w) Acetone, Hz0 (40% w) Acetone, Hz0 (60% w) DXN, Hz0 (20% w) DXN, Hz0 (40% w) DXN, Hz0 (60% w) SUC, H,O (10% w) ETG, Hz0 (10% w) Hz0 -0.01 M HN03
k AH* AS*
1.7 x lo4 23.7 -5.5 1.7 22.9 -8.1 2.1 24.8 -1.3 1.7 23.1 -7.4 1.8 22.9 -8.0 1.9 22.6 -9.0 1.1 22.7 -9.5 1.2 22.6 -10.0 1.3 23.3 -7.4 3.1 x 10” 27.5 13.1 3.8 29.4 19.9 2.2 26.4 8.7 1.5 24.5 1.6 0.94 22.3 -6.7 2.4 26.2 8.2 1.7 25.7 5.9 1.6 25.6 5.4 2.3 26.8 10.1 1.6 25.8 6.1 1.4 24.5 1.4 2.3 26.3 8.5 1.9 24.4 1.7 1.5 24.2 0.5 4.2 26.3 9.5 - 25.1 8.7 4.9 27.3 13.3 3.5 26.1 8.6
a These reference numbers refer to the list entitled Data Table References.
Ref.a
q,40 85 86 87 88 89 89 89 89
161 162 162 162 162 162 162 162 162 162 162 162 162 162 156 158 134 163
Ligand Replacements in Octahedral Complexes
entropies span an 8 cal mol-’ deg’ range. The variations for truns-Co(en)ZCl,+ are considerably larger. Such differences are not likely to be due com- pletely to differing reaction conditions; rather they probably stem in part from arbitrary evaluation of the d H * values.
These data are presented in Figure 2 which shows that dH* (or E,) and dS* are for each complex fairly well correlated by a straight line. This situation is expected when AG* is essentially constant and a random error has crept into the calculation of AH*,
for instance, from an arbitrary choice of the slope of .the plot. The error in AH* must then be compensated for in the evaluation of AS* from AC’ and AH*
The slopes of the lines for the three complexes are about 280°K (i.e., reasonably near to the tempera- ture range of the experiments).
The line from the student data is shown on Figure 2 for comparison. Although the slopes are different in the several cases (600°K for the student data, and about 280°K for the coordination compound data), the hazard in simply putting a straight line to a series of points is clearly revealed. It is our contention that, all too often, the activation parameter data in the mechanism literature suffer from this subjective treat- ment of the rate data. Sadly, the errors in the resultant numbers are sufficiently large to hide interesting and real differences.
Most of the reactions of octahedral coordination compounds are carried out in aqueous solution. The reason is related to the solubility properties of the compounds; they are usually too poorly soluble in non-aqueous solvent systems to allow significant ex- perimental investigation.
It is a fairly common practice to add along with the reagents some “inert” (in this context, non-reac- tive) salt, such as alkali metal nitrates or perchlorates, in order to keep the ionic strength constant. It is questionable how inert such salts are, since although the anionic component of the salt may not behave as a reactant in the ordinary sense (e.g., as a ligand), it may interact with the octahedral substrate, especially when the substrate is cationic, with the formation of ionic associations having kinetic relevance. Perchlo- rates, which have been thought to be more safe to deal with, probably behave like the other mononega- tive ions.16 The general question is, however, far from settled and should be given more attention in the future.
The criterion of “constant ionic strength” has also been criticized”’ ” for those cases where the com- position of the ionic species is changed markedly. This happens often when the kinetic effect under investiga- tion is relatively small, so that for detection of the effect a variation of the concentration over a large interval is required. Actually, when the ionic strength is higher than O.lM, there is little justification for
51
assuming the constancy of activity coefficients at con- stant ionic strength but changing ionic nature. More- over it is possible that under such conditions the ex- perimental results could conform better to simple limiting laws such as the mass action law.
Only a few systems have been studied over a suffi- ciently wide range of ionic conditions (i.e., ionic nature and ionic strength) to allow judgment of the influence on activation parameters. In general, the variation in the parameters seems to be more random (as described above for the subjective evaluation) than rational. Nevertheless, it would be desirable that chemists work- ing the area of coordination compound mechanisms be aware of the possibility of selecting reaction condi- tions which would allow ready comparison of their data with those obtained by other workers.
At present, there are two practices. One is to extra- polate rate constants (and, less often, activation parameters) to zero ionic strength. The other is to carry out experiments at a given constant ionic strength so that all of the kinetically relevant data are referred to that fixed condition. The first practice is perhaps preferable on the basis of the fundamental concepts of physical chemistry, but it necessitates a time-con- suming procedure and leads to data which may not be directly comparable to those obtained at high ionic strength. The second practice is often necessary when, as we pointed out above, the concentration of a re- agent must be varied over a wide range to detect a particular kinetic feature. This happens, for instance, in the study of the anation reactions of complex ca- tions when the interchange rate constants of the ion- pairs have to be measured. In these cases, the extra- polation of the experimental data to zero ionic strength is essentially impossible since the lower practical limit of the ionic strength cannot be set much below OSM.
This ionic strength value may be considered roughly the border between those conditions (of the ionic me- dium) chosen when an extrapolation to zero ionic strength is possible and those when the concentrations must be kept high. It would be desirable that in both cases the experimental conditions were chosen in such a manner as to allow at least an extrapolation of the relevant kinetic data to this common value (0.5M) of ionic strength.
3. Symbols and Notations
A. General
The reactions for which data have been collected in the following tables are in order: solvolytic reactions in aqueous and non-aqueous media, acid-catalyzed aquations, base hydrolyses, isomerizations, and ana- tions and overall second-order ligand substitutions. Most of the notations and symbols used here have obvious meanings since they are those currently em-
52 J. 0. Edwards, F. Monacelli and G. Ortaggi
ployed in the literature. Some points, however, need explanation.
tetren = tetraethylenepentamine
a) Within each reaction type, the metals follow the order of increasing atomic number; b) In the formula for the complex, the last l&and on the right is the one which is replaced or reacts and is written beginning with the donor atom; c) We have been unable to find a good general criterion for listing all the complexes. We decided to group the compounds of a given metal ion undergoing the same general type of reaction into classes according to the nature of the five inert donor atoms. At least three (out of the five) donor atoms are considered to identify a class. Compounds not belonging to a class as above defined, have been listed in the last part of the table.
cytam tu tmd DXN ETG sue tet-a
tet-b
trans[ 14]diene
= 1,3,5-triaminocyclohexane = thiourea = 1,3-diaminopropane = dioxane = ethylene glycol = sucrose = C-meso-5,7,7,12,14,14_hexa-
methyl-1,4,8,11-tetraazacyclo- tetradecane
= C+-5,7,7,12,16,16_hexame- thyl-1,4,8,1 l-tetraazacyclo- tetradecane
= 5,7,7,12,14,14-hexamethyl- 1,4,8,11 -tetraazacyclo-tetra- deca-4,ll -diene
B. Reaction Conditions In aqueous media, the pH (or pH range) and the
ionic strength ,U (or ionic strength range) are indicat- ed. Negative pH values correspond to hydrogen ion concentrations higher than lM, with the defining equation being pH = -log[H+]. Also the nature of the electrolyte present in the medium is given. Often the reactions are carried out in the presence of mixed electrolytes. Whenever possible shorter notations like (Na,H)C104 for NaC104 + HC104, or (K,Ba/2,La/3) Cl for KC1 + BaClz + LaCL have been used. When no electrolyte other than the complex itself are used, “none ” appears in the column headed Medium; in these cases, the counter ion is specified within brackets, <>, under Comments. When non-electrolytes like methanol or sucrose are added to solvent water, they appear under Medium together with the added electro- lytes (if any). Sometimes the amount of non-electro- lyte is shown as a molar ratio, or as a weight percent (w), or as a volume ratio (v).
C. Abbreviations The following is a list of the less common abbrevia-
tions which have been used for compounds:
bn
pn tet-me
Me-en Et-en n-Pr-en tn dan cyclam
2,3,2-tet tren trien TMS dien
= Butylenediamine = Propylenediamine = (C,C,C’,C’)-tetramethyl-
ethylenediamine = N-methylethylenediamine = N-ethylethylenediamine = N-n-propylethylenediamine = NHz(CH&NHz = NH2CH2C(CH3hCH2NH2 = 1,4,8,11 -tetraazacyclo-
tetradecane = 1,4,8,11 -tetraazaundecane = P,P’,/I”-triaminotriethylamine = triethylenetetramine = sulpholane = diethylenetriamine
D. Rate Constants and Activation Parameters The rate constants given in the column designated
k are at 25’ C if not otherwise denoted aside. The time unit is set, and for the second-order con-
stants the concentration units are mol liter-’ (M-l). When necessary and possible, the values of k at 25’ C have been calculated by use of the enthalpy of activa- tion and the experimental rate constant nearest to 25 “C. Those cases where values of k for other tem- peratures are given correspond to systems studied at only one temperature and have been included either when no other kinetic data are known for the same system or to allow a comparison with data obtained in different studies. In some cases, the rate constant at 25” C has been calculated by using dH*, dS* and the Eyring equation. These values have been listed in parentheses, ().
Enthalpies and entropies of activation are given as kcal mar’ and cal mar’ deg-’ respectively. Some dH* values have been obtained from measurements at only 2 temperatures and/or with a particularly nar- row temperature range and so are felt to be less re- liable than the others. This is indicated under the column Comments by the symbol (2~) and/or by the width of the temperature range explored. The un- certainties in d H* and d S* are not given explicitely in the tables. However, when they are estimated to be higher than 1’ kcal mar’ and 3 cal mar’ deg-‘, the numbers are underlined. The units of dV* are cc mol-’ . Many entropy data have been calculated by us, since in some cases this calculation had not been car- ried out by the authors of the work or they had calcul- ated it in the original article as a pre-exponential factor or equivalent.
In some cases we have found appreciable discrep- ancies between dS* given in the literature and those calculated by us using the rate constant and the activa- tion enthalpy given by the authors. Some of these discrepancies were due to incorrect employment of the activation energy E, (instead of the activation en-
Ligand Replacements in Octahedral Complexes
thalpy) or to the use of the minute as time unit for k while the Planck constant was expressed on the se- cond scale. In such cases, the dS* values listed are those calculated by us. Whenever the reason for the observed discrepancy remained unexplained, the result of our calculation has been given in parentheses, to- gether with the original value.
The rate constants k1 of the kinetic term k-r [H+]-’ of the aquochromium(II1) complexes have been converted into the corresponding ken rate constants (base hydrolysis) by setting ken = kr/Kw. Consequently, the activation parameters have been corrected for the standard enthalpy and entropy of the process Hz0 P OH- + H+, (AH = 13.3 kcal mar’ andd S = -19.3 cal moT’ deg-‘).
All of the calculations have been carried out with the use of an Olivetti 101 desk computer.
53
E. Experimental Methods
The technique adopted for each kinetic study is indicated by a symbol under the column Method. The following is the list of symbols and corresponding technique used:
A C co D esr K G M nmr nmr(lb)
P PH pH stat Pm R S S fm
S sf
Stj
T Tr
= amperometric method = calorimetric method = calorimetric method = densitometric method = electron spin resonance method = conductometric method = gravimetric method = mass spectrometric method = nuclear magnetic resonance method = nuclear magnetic resonance line broad-
ening method = polarographic method = potentiometric pH measurement = constant pH titration method = polarimetric method = radioactive isotope labelling technique = spectrophotometric method = spectrophotometric method (w. fast
mixing) = spectrophotometric method (w. stop-
ped-flow) = spectrophotometric method
(w. T-jump) = titrimetric method = titrimetric method (w. flow apparatus)
F. Remarks and Comments
In some instances (aside from the activation param- eters and similar types of data in specifically designated columns) in the column headed Comments, short re- marks have been included. These concern, as a rule, clarifications of some aspect of the specific system studied (such as stereochemical course or position of
bond breaking), the nature of the counter ion (where given), and any further observations that we feel are useful for a better understanding of the data and me- chanism. When indicating the dependence of rate parameters on reaction conditions such as reagent concentration, short notations have been adopted. The following is a specific example: kt[H+]t signifies that the rate constant increases (t) with increasing ( t) hydrogen ion concentration.
Other remarks and comments are also found in the table footnotes.
The review has been put together with different sets of tables and references. The tables used to show speci- fic points relative to textual material are placed at appropriate sites, and in many instances the relevant references are cited in the list of Text Reference pre- sented at the end of the text. On the other hand, the tables containing the compilations of literature data are located at the end of the review and are termed Data Tables; the citations for these data are placed in Data Table References. The two types of references (i.e., for text material and for data tables) are number- ed separately. Although this results in some redund- ancy in the references, it is felt to be more flexible and to minimize the possibility of numbering errors.
4. Metal Oxidation State and Size
The emphasis in this review is on coordination com- pounds having the central metal atom in the +3 oxida- tion state. For completeness, however, we give here a brief discussion of the influence of oxidation state on the rates of ligand replacement. We consider that the effect of oxidation state is primarily electrostatic in nature (ion-ion, ion-dipole, etc.).
With few exceptions (e.g., Mn(CN)6s-), rates of replacement for complexes with central metals in +l oxidation state are very fast. The +l hydrated cations (alkali metal cations, Ag+) have water exchange rate constants in the vicinity of 10” with small variation of alkali metal cation rate with size (Cs+ > Rb+ > K+ > Na’ > Li+). This is the expected pattern for rate varia- tion, whether the mechanism be associative or dis- sociative, and little other data with mechanistic implica- tions are available.
For the coordination compounds having metals in the +2 oxidation state, most of the complexes fall into the category termed “labile” by Taube.’ With the newer fast reaction techniques, many ligand replace- ment rates have now been measured. Some relevant reviews are available.9’107’3 The data in the review of Wilkins13 suggest that replacement reactions in octa- hedral nickel(II) complexes follow an interchange mechanism not unlike that observed with complexes of cobalt(II1).
54
The influence of oxidation state also is seen in the behavior of platinum(IV) complexes. These are so inert towards a dissociative interchange mechanism ‘that more complicated, indirect paths for ligand re- placement predominate. Catalysis by base, by Pt(II1) intermediates, or by Pt(I1) complexes, even though slow, carry the bulk of replacement.
The influence of central atom oxidation state can, to a significant degree in some cases, mask the effects of electronic structure. Both ligand fields and metal oxidation states are important in determining rates of ligand replacements. Their individual and combined influences on the mechanism (as contrasted to the obvious influences on overall rates) could well be the subject of an interesting review. For the present re- view, we shall for practical reasons restrict our atten- tion to octahedral complexes of metals in oxidation state plus three.
If one has two metal ions having different sizes but with the same coordination number and electronic configuration (as, for example, in the complexes of cobalt(II1) and rhodium(III)), an entering ligand is more readily bonded to the larger metal as the leaving group moves away. In terms of the octahedral wedge transition state, the interchanging ligands both can be less far from the “surface” of the metal at the point of a transition state. The value of AH* will be lower and of AS* more negative for the larger cation. The mechanistic conclusion is that one can say that the reaction may have a greater fraction of associative character as size increases.
The predicted change in AS* value with metal ion size is seen in the data for hydrolysis of complexes hav- ing the d6 low spin electronic configuration shown in Table IV. The decrease in AS* from -2 for the cobalt complex to -6 for the rhodium complex and the further decrease to -16 for iridium when trifluoroacetate is the leaving group are believed to result from the in- crease in associative character with metal size. The changes in AH* are barely above the level of experi- mental error. The predicted decrease in AH’ expected from the increase in metal size is presumably com- pensated for by the contribution to activation enthalpy
TABLE IV. Activation Parameters for Hydrolysis in Acid Solution of Trifluoroacetato and Nitrato Complexes.
Complex AH* AS* Ref.a
(NH&ZOO~GF~~+ 26 -2 97 (NH3)sRhO&F3’+ 25 -6 97 (NH&~OZC~F~*+ 24 -16 97 (NH3)&oN03*+ 24.3 1.9 94 (NH3)5RhN03*+ 23.3 -3 160 (NH~)~I~N~~~+ 26.1 -4 160
a These reference numbers refer to the Data Table Refer- ences list.
J. 0. Edwards, F. Monacelli and G. Ortaggi
due to ligand field stabilization which increases in the order Co < Rh < Ir. When nitrate ion is the leaving group, the expected trend in AS* values is again seen and no clear trend in A H* values is apparent.
Another factor that can be important in determining the details of mechanism and that is related to metal ion size is orbital extension. The filled d orbitals of the central metal ion for low spin complexes of Co(III), Rh(II1) and Ir(II1) have different extensions in the space around the metal. Depending on the bonding, non-bonding, and antibonding character, orbital over- lapping will influence the energy of the transition state. Since the number and importance of the several inter- actions possible depends on the nature of the atoms, we cannot discuss it here; suffice it to say that the in- fluence of metal ion size and nature on the orbital length and hence on the efficiency of overlapping will have to be er tions.
5. Acid Hydrolysis
llored in more detailed investiga-
Aquation)
As a reference point, we shall employ the aquation of cobalt(II1) complexes. There are a large number of results which indicate that the mechanism involves dissociative interchange. The published’3334,s,“,9314 data (e.g., for AS* , AV’ , rates with sterically-hinder- ed ligands, lack of discrimination between incoming nucleophiles, and the linear free energy relation be- tween leaving ligand rates and equilibria) can be satisfactorily explained on the basis of this I,, model. The bond between cobalt and the leaving ligand is considerably stretched, and the new bond between metal and entering ligand (here water) is little formed. In most cases, one sees retention of geometric con- figuration during replacement suggesting that the entering water molecule drops into the hole which is in process of formation on departure of ligand. Con- cerning this mechanism, we concur with Rosseinsky” who - in another mechanistic context - has said “Se non & vero, 2 hen trovato”. Roughly translated (provided, of course, that he does not object to our addition of the two accent marks), this means “Even
if not the truth, it is well founded”. At first sight, there seems to be little new in the
collected data on aquation reactions which leads to definitive conclusions. Some representative data for cobalt(II1) and rhodium(II1) are shown in Table V. The reaction in each case is replacement of ligand Y by HzO. The activation enthalpies do not appear ex- ceptional (i.e., not too high or not too low) and the entropies fall not too far from zero. Nevertheless, careful inspection of the numbers indicates that some conclusions are warranted. For example, for each of the six cases where comparison can be made, the value
Ligand Replacements in Octahedral Complexes
TABLE V. Rates and Activation Parameters for some Octahedral Aquation Reactions.”
55
Rh(III) Co(II1)
Y- k dH* AS* Ref.b k
I. For M(NH3)gY 2+
NOa- 1.2 x 10-5 23.3 -3 160 2.4 x 10” so,*- 1.6 x lo-+ 21.4 -13.3 102 8.9 x 1o-7 CFaCOz- 2.0 x lO-’ 25 -6 97 1.5 x lo-’ I- 6.2 x 1O-9 26.2 - 7.8 181 8.3 x 10” Br- 3.4 x lo* 24.6 - 9.9 187 6.5 x lo-+ CT 3.8 x 1o-a 24.2 -11.1 187 1.7 x lo+
II. For tranr-M(en)zClY+
cl- 5.4 x loa 24.7 -9 190 3.1 x 1o-5 Bi 8.3 x lo+ 27.6 -3 190 1.1 x lo4
a Rate constants have units of see-’ and were taken at 25’ C. b These reference numbers refer to the Data Table References. ’ The data for Co(NH3)JZ+ are complicated by a concurrent redox process.
AH* AS* Ref.b
24.3 + 1.9 94 22.7 -10 102 26 -2 97 19 -16 90’ 23.9 - 3.0 85 22.9 - 8.1 85
27.5 +13.1 161 26.0 +10.6 136
of dS* for the cobalt complex is more positive than for the rhodium complex.
The activation entropies for the solvolysis of com- plexes of the type ML5XZ+ (where M = Cr, Rh or Ir and L = NH3 or HzO) are almost always lower than those for CO(NH~)~X*+ which we have taken as the reference. From the direction of this difference, we can infer that there is more associative character in the replacement mechanisms for Cr, Rh and Ir than for Co. This is in agreement with conclusions in the litera- ture based on other types of mechanistic information.”
As the associative character of the replacement in- creases, there should be a tendency towards decreased enthalpy of activation. All other things being equal, the energy of the bond being formed partially com- pensates for the energetic cost of bond-breaking. The activation enthalpies of the other complexes are usually lower than those for the analogous cobalt complexes, although there certainly are exceptions. The factors influencing rhodium(III) and cobalt(II1) enthalpies are probably balanced, so that the previous generaliza- tion” dH* rr >dH* Rh >dH*,c, must now be accepted with caution even if occasionally true; once again the data in Tables IV and V are interesting in context.
The compilation of data for aquations of complexes is presented in Data Table I below.
One group of ligands (including F, CN- and N3-) appears to be exceptional in terms of activation param- eters for their aquations. A case in point is Cr(H20)5 X2’. The postulated mechanism is
Cr(Hz0)5X2C # Cr(H,O),(OH)(XH)*+ (fast)
Cr(H,0)4(0H)(XH)2C+ Cr(H20)4(OH)2+ + HX (rate)
Cr(H20)4(0H)2+ + H30++Cr(H20)63+ (fast)
(The possibility that Hz0 from solvent participates directly in the rate step to form Cr(H20)5(OH)Z+ cannot be excluded, however we shall ignore this pos- sibility at this point.) The ligand XH should be a bet- ter leaving group than X- and the concurrent con- version of Hz0 to OH- in the coordination sphere should release electron density to the central atom making the loss of XH easier. Therefore, the overall effect of the change in proton position should be a rate enhancement. The ligands X- involved in this mechanism turn out to be the same ligands as those which undergo acid-catalyzed aquation (see below), and this is not surprising as placement of a proton on X- is an important aspect of both mechanisms. Con- version of Hz0 in the coordination sphere to OH- is quite analogous to the base hydrolysis mechanism discussed below.
The evidence for this type of proton tautomerism is not compelling on the basis of our activation param- eter compilation, however the mechanism is a reason- able one. The aquation of Cr(NH3)5F2’ does seem somewhat exceptional.
Considering aquations in general, the activation entropies are not far from zero, and this is not un- reasonable for an interchange mechanism. Neverthe- less, no clear trend between either dH* or dS* and the nature of the leaving group is apparent in this table. It is interesting to note that the values of dH* are practically insensitive to the overall electrostatic charge on the complex. One can speculate that the Coulomb contribution to the metal-ligand interaction energy is hidden among other charge effects, as for example in solvation of ground state and/or transition state.
In principle, the data for aquation of similar cis and trans complexes can be employed to explore the pos-
DA
TA
TAB
LE
I. A
quat
ion
(Aci
d H
ydro
lysi
s).
Com
plex
p(
m)
PH
Med
ium
k
- (N
a,H
)C10
4 1.
0 10
.7
-22.
6 C
r(H
20)s
(tetre
nI%
)‘+
4 _
HC
lO.,
-8.0
X
lo4
28
.9
1.4
6+
Cr(
HzO
),(tri
enH
3)
2.0
_ H
ClO
z,
I x
lo+!
27
.5
- 2.
9
1.0
o-1.
7 (L
i,H)C
104
Cr(
HzO
),B?’
1.
0 o-
1.3
(Li,H
)C10
4 C
r(H
zO)s
BrZ
+ 2.
0 SO
.6
(Na,
H)C
104
0.4-
0.67
1
(Cr/3
,H)C
lOh
2.06
51
.3
(Na,
H)C
lO.,
0.17
1
HN
03
1.0
1.0
1.0
1.0
1.0
04.7
(L
i,H)C
104
1.07
O
-O.6
(N
a,H
ClO
,
1.0
1.0
2.06
51
.3
(Na,
H)C
lO,
9.2
X 1
0”
26.9
8.
9
1.0
0.4-
3.2
(Li,H
)ClO
., 4.
1 x
lO+
32.4
16
.4
o-3
-0
-0
o-1.
2
o-1.
7 o-
3.1
Tabl
e R
ef.
No.
(Na,
H)C
104
(Li,H
)ClO
,,
(Li,H
)C10
4
(Li,H
)C10
4
(Li,H
)ClO
,, (L
i,H)C
104
2.3
X 1
0-s
3.2
x 10
” 8.
7 X
lo-’
(40”
) 1.
2 x
lo4
6.5
x 1o
-5
5.0
x 1O
P
6.2
X lo
--”
2.8
X lo
-’
4.3
x IO
4 9.
0 x
10”
(30”
) 6
x 10
-s
1.5
x 10
” (3
0”)
8.4
X l
o-’
1.2
x 10
-s
26.1
7.
8 16
.2
-15.
6 -
_
27.2
-
3.5
21.9
-
4.2
21.8
-
5.1
28.7
-
4.4
24.3
-
7.0
23.8
-
3.2
_ _
28.0
16
.1
- _
23.0
-
0.2
27.9
12
.7
S SF
S
S
S
S
S
D;<
CT>
; H
Cl
(but
no
t N
aCl)
is r
epor
ted
to
caus
e th
e im
med
iate
ex
chan
ge
of t
wo
Hz0
m
olec
ules
M
; (2
T,7’
C
ran
ge)
S S
1 33
2 30
9 30 2 3 5
S
4 7 6
325
S 8
S S; C
r(H
20)4
(OH
)(FH
y’
is s
ugge
sted
as
the
re
activ
e sp
ecie
s S S S
8 9
SC
S S S; C
r(H
20b(
OH
) (H
CN
)*+
is s
ugge
sted
as
the
re
activ
e sp
ecie
s S;
Cr(
H20)4
(OH
) (H
CN
)‘+
is s
ugge
sted
as
the
re
activ
e sp
ecie
s S;
Cr(
HzO
)d(O
H)
(NaH
)*+
is s
ugge
sted
as
the
re
activ
e sp
ecie
s
9 10
11
12
13 9 74 7 15
frun
s-C
r(H
zO)a
Clz
’ 1.
0 H
Cl
8.2
x 10
-s
25.9
trans
-Cr(
H20
)4C
l~+
0.5
l-l.3
7 (N
a,H
)Cl
8.3
x 1t
F _
cis
+ tr
am-
Cr(
H20
)4
(NC
S)SC
N+
1.0
o-1
(Na,
H)C
104
1.1
x 1o
A
19.6
C
r(H
20),(
tetre
nH3)
6f
4 -0
.6
HC
l04
3x10
” 25
.3
Cr(
H,O
)s(C
N)(
NO
)(H
CN
)‘+
cis-
Cr(
H2O
),(N
H,)C
l,+
[run
s-C
r(H
ZOh(
NH
a)C
lz+
1.0
1,2,
3-C
r(H
,O)s
(CN
)(H
CN
)’
2.0
Cr(
NH
3)sO
Hz3
+ 1.
7 C
r(N
Ha)
50H
Z3+
0.40
C
r(N
Hs)
5N3H
3+
8.0-
10.8
2.0
0.33
1.0
1.0
1.0
5-11
1.
0
2.0
1.0
2.0
1.0
3.0 1.0
1.7
0.25
-1.5
_ 4 1.
0 1.
0 1.
0 1.
5 3.
0
1.7
1.0
SO.6
(N
a,H
)C10
4
0.82
(N
a,H
)C10
4
2 (N
a,H
)ClO
.,
O-l.
1 O
-1.0
o-1.
3
0 o-1.
3
20
<o
(Li,H
)ClO
,, (L
i,H)C
104
HC
l04
(Li,H
)C10
4
(Na,
HM
04
(Li,H
)ClO
, H
CIO
., (N
a,H
)C10
4 H
ClO
, H
Cl0
4
- (N
a,H
)C10
4 ~0
.6
HC
l04
- _ H
Cl0
4
O-O
.82
20
o-1
co.5
(Na,
H)C
104
(Na,
H)C
lOd
(Na,
H)C
lO,,
HC
l04
(Na,
H)C
104
(Na,
H)C
lO,,
04.5
(N
a,H
)C10
4
o-o.
5 (N
a,H
)C10
4 -0
.2-1
.0
(Na,
H)C
104
1.3
(Na,
H)C
104
1 H
CIO
, -
HzS
O4
6 x
lo-’
(4
0”
C)
9.1
x lo
-+
- -
S 16
27.5
-
3.0
1.7
x 1o
-5
23.5
-
1.6
7.2
x 10
” 21
.4
- 5.
7 7.
7 x
10-s
21
.6
- 5.
1 7.
4 x
1o-3
14
.7
-19.
0 _
-33
-
1.4x
1F
20
.2
-17.
7 7.
5 x
lo-7
21
.9
-13
4 x
lo-’
23
.6
-9
3.1
x lo
-’
23.4
-
9.8
2.2
x 10
” 27
.1
-3
4.3
x 10
” _
_ - 9.
3 (+
9.7)
- -
9.8
-6
5x
10”
13.3
-2
4 4.
8 x l
o-’
24.4
-6
(8
.2
x 10
”)
12.6
-3
5 2.
7 X l
Od
24.5
-2
1x10
-+
26.9
8.
1 x
lo-’
23
.7
5.3
x l@
18
.6
3.0
x ltr
’ 26
.8
3x10
-+
21.4
2.5 x 1
O-3
19
.7
2.8
x lo
@
22.5
4.8
x 1F
19
.6
5.8
x lo
4 16
5.
47
x 10
-s
22
5.24
x
lo-’
23
.2
1.59
x
lo4
19.1
4.0
- 6.
9 -1
1 1.
7 -
7.4
(-
12)
F46.
3)
ZU
(-3.
9)
-13
-19
-4
0.0
-11.
8
S; S
N2
beha
vior
is
su
gges
ted
S;dS
* =
+l.O
if
the
trans
ition
st
ate
is t
he
sam
e fo
r bo
th
aqua
tion
and
Cr-
S +
Cr-
N
isom
S S S
(2T)
S;
A H
* va
lue
refe
rs
to
Cr-
0 cl
eava
ge
S S S S S S; c
is
to P
ans
isom
. w
as
not
acco
unte
d fo
r
S (2
T,
15’
C r
ange
)
17
18
19
20
21
22
23
24
309 30
3 27
27
S S S; s
ubst
rate
is
a m
ixtu
re
of i
som
ers.
Prod
uct
is
Cr(
HZO
)S(te
trenH
.,)7f
28
331
332
esr
ST
- S; p
rodu
ct
is C
r(H
zO)d
(te
trenH
3)6+
S S S ST
ST
25
26
29
332 31
30
30
32
33
esr
25
ST
26
ST
26
S 27
9 M
;k?
pHt
34
M;
[com
plex
] =
0.05
M
318
S 35
DA
TA
TAB
LE
I. (C
ont.)
Com
plex
p(
m)
PH
Med
ium
k
AH
’ A
S+
Cr(
NH
3)50
NO
zZ+
Cr(
NH
,),O
CO
CF,
*’
Cr(
NH
&O
CO
CC
lsZ+
C
r(N
H3)
50S0
3+
Cr(
Me-
NH
*)&
1 *+
1.0
0.1
0.1
_ 1.0
0.5 0.1
0.2 1.0
0.10
6 - _ _ 1.
0 0.
1 0.
2 1.0
0.1
0.2
0.1-
0.2
0.06
0.
2 0.
07
0.10
6 1.
3 (N
a,H
)ClO
,, 4.
1 x
lo-’
29
.6
11
1.0
0.01
0 0.
10
0.13
0
(ext
.) 1.
0
1.0-
l .3
(N
a,H
)C10
4 3.
70x
10-l
21.3
7
NaN
OS
9.7
x lo
4 26
.0
l-10.
5 (N
a,H
)(C
104,
OH
) 2.
54
x lo
-’
24.4
14
- 8.
0 x
lo+
21.8
H
ClO
‘, 7.
3s
x 10
” 23
.6
(Na,
H)C
lOd
6.8
x 10
” 22
.2
l-10
(Na,
H)(C
lO~,
OH
) 9.
3 x
lo4
1-2
~Na,
DW
04,(
D20
) 5.
6 X
10d
0.
4 (N
a,H
)C10
4 3.
9 x
lo+
1.3
(Na,
H)C
104
6.8
x 10
” -
MeO
H
: Hz0
6.
0 x
10”
1 :4
..5
(m)
_ Et
OH
: H
Z0
6.0
x lO
A
1 :4
.5
(m)
- 5
x 10
-s
HC
lO‘,
6.X
x
10”
l-10.
0 W
,H)(
CK
kOH
) 1.
0 x
lOA
l-2
(N
a,D
FXM
D20
) 9.
8 x
lo-’
H
ClO
a 7.
8 x
1O-3
(2
6°C
) l-1
0 (N
a,H
)(C
KL
OH
) 1.
0 x
1o-3
l-2
(N
a,H
W0d
D20
) 1.
5 x
1o-3
1.
2-2
(Na,
H)C
lO.,
3.6
x lo
4 2.
5 H
ClO
z,
9.3
x lo
4 l-2
W
a,D
)C10
dD20
) 4.
0 x
lo-
1.5
HC
l04
8.7
x lo
4
slig
htly
K
N03
3.
2 x
1om
5 ac
idic
(N
a,H
)OC
OC
Hz
HC
l04
7.0
x lo
+ 1.
03-1
.72
(Li,H
)CI0
4 8.
7 x
lo4
l-2
(Na,
H)C
104
3.6
x lO
A
- _
1.2
x lo
4 0.
4 (N
a,H
)C10
4 (7
.0
x 10
”)
10.8
-
3.4
- 4.
6 (-
6.8)
-
8.7
- 2.
8 -8
21.8
-
8.4
22.4
-
7.5
22.3
-
8.5
20.7
-1
2.7
21.5
-
10.3
21.6
-1
0.0
22
- 4.
4 23
.9
2.6
20.9
-
6.7
22.3
-
2.1
_ -
20.8
-
2.5
22.4
3.
7 26
.3
- 4.
9 24
.9
- 7.
2 24
.6
- 9.
8 24
.7
- 8.
0
34.4
21.0
20
.2
21.5
(22)
36.3
-3
-2.5
(-
13
.9)
-11.
3
(-13
)
Com
men
t Ta
ble
Ref
. N
o.
SW
36
T
38
P;S
39
- S S; k
ind
ep.
of p
H
but
dep.
on
p P P S;
k t
[H+]
&
(bas
e ca
t.)
S T
q 40
37
43
41
44
42
34
45
T 45
_ S P P S; D
iffic
ultie
s fro
m
solu
bilit
y pr
oble
ms
P P S; (
10”
C r
ange
) S P S,
T;A
H*
andA
S*
are
give
n fo
rp
ext.
to 0
S;
Not
e th
e la
rge
disc
repa
ncy
rela
tive
to
othe
r da
ta
on
the
sam
e co
mpl
ex
S
cl 4
0 37
41
44
37
41
44
326 40
44
46
34
213
S S 48
49
S S T; k
t [H
+]J.
(bas
e ca
t.)
320 50
42
Cr(
Et-N
H2)
sC1*
+ C
r(A
ll-N
H2)
&lZ
+ ci
s-C
r(N
Ha)
4(H
zO)C
12+
cis-
Cr(
NH
3)4(
H20
)C12
+
cis-
Cr(
NH
3)4(
HzO
)IZ+
ci
s-C
r(N
H3)
4(H
20)1
2+
cis-
Cr(
NH
3)4(
0H)I
C
trans
-Cr(
NH
3)4(
H20
)CIZ
+
trans
-Cr(
NH
3)4(
HzO
)Cl*
+ tru
ns-C
r(N
H3)
4(H
20)B
rZ+
truns
-Cr(
NH
a)4C
h+
trans
-Cr(
NH
3)4C
1Br+
tra
ns-C
r(N
H3)
4ClI+
trans
-Cr(
NH
a)dB
rCl+
tru
ns-C
r(N
H3)
4(0H
)If
Cr(
NH
3)4(
NC
S)N
HsZ
+
twin
s(?)
-Cr(
en)(
HzO
hBrZ
+
trans
(?)-
Cr(
en)(
NH
a)(H
20)B
rz+
Cr(
en)(
H2O
)Klz
+
trans
-Cr(
en)F
z(en
)+
trans
-Cr(
en)(
NC
S)2e
n+
cis-
Cr(
en),(
H20
)C12
+ ci
s-C
r(en
)Z(H
20)B
f+
cis-
Cr(
en)z
(HzO
)NC
S2+
ci.s-
Cr(
en)z
Clz
+ ci
s-C
r(en
)&&
+ ci
s-C
r(en
),Clz
+ ci
s-C
r(en
),Br*
+ ci
s-C
r(en
)2(N
a)2+
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
-0
1.0
2.0
0.3
0.1 1.0
0.01
0 0.
10
0.4
0.4 1.0
(Na,
H)C
104
3.3
x lo
-’
26.0
(N
a,H
)C10
4 2.
9 x
lo-’
26
.0
(Na,
H)C
104
2.0
x lO
A
21.4
H
C10
4 5.
4 x
10”
21.3
l/[H
+]
(Na,
H)C
lOd
8.0
x 10
-s
20.2
ex
t.to
0 O
-l.78
l/[
H+]
ex
t.to
0 12
-14
l/[H
+]
ext.
to 0
O
-l .7
8 l/[
H+]
ex
t. to
0
04.7
o-
o.7
o-1
o-o.
7 12
-14
O-O
.8
SO.5
0.5-
l
l-2
(Na,
H)C
lO.,
1.1
x 10
” 19
.7
-6
S 32
7 (N
a,H
)ClO
d 8.
5 x
lo4
20.2
-
4.9
S 35
2
Na(
C10
4,0H
) 6.
3 17
.0
HC
104
8.6
x 1o
-7
23.4
HC
lO.,
6.5
x lo
-’ 23
.3
(Na,
H)C
104
1.0
x 10
-s
21.6
2 -
7.8
- 9.
5 -
9.4
(-4.
4)
-5
- 6.
7
S S,T;
29
0%
tran
s pr
od.
- S
327 51
q 35
2 35
2
(Na,
H)C
lO.,
(Na,
H)C
104
(Na,
H)C
lOd
(Na,
H)C
104
(Na,
H)C
104
7.4
x 10
-s
9.5
x lo
-5
S 32
7 S
352
4.9
x 10
” 3.
1 x
lOA
3.
3 x
lOA
21.4
20
.9
21.0
20
.2
18.0
S; 2
92
% t
ram
pro
d.
51
S; 2
95
% b
ans
prod
. 51
S
327
(Na,
H)C
104
Na(
C10
4,0H
) N
aOH
(Na,
H)C
104
2.9
x lo
-4
19.5
2.
1 18
.7
3.9
x lo
-’
28.5
S; 1
00%
tr
am p
rod.
51
S
327
S 21
3
4x
lo4
22.6
- 7.
8 -
6.8
(_?4
) -
9.3 5.5
11.9
(7
.8)
- 7.
0 S,
T;
prob
able
co
nfig
. fo
r B
r- an
d a
Hz0
m
olec
ule
31
(Na,
H)C
lO.,
4.0
x l@
19
.2
- 9.
2 33
(Na,
H)C
104
4.1
x 10
” 20
.1
- 7.
0
(Na,
H)C
lOa
24.7
3.
8
24.1
-
0.3
ST;
prob
able
co
nfig
. re
fers
to
the
B
r’s
S,T;
pr
obab
le
conf
ig.
refe
rs
to t
he
Br’
s
ST
31
3.1
x 1o
-5
32
0.24
-1.3
6 (N
a,H
)C10
4
HN
O3
HN
Oa
0.06
4.14
H
ClO
., 0.
75
HC
104
0.10
H
NO
Z 0.
10
HN
Os
- _
none
0.
1 l-2
(L
i,H)C
lOd
0.4
2.12
(N
a,H
)ClO
d
1.2
x 10
”
3.5
x 1f
P 2.
8 x
10-s
1.
8 x
lo4
1.5
x lo
-+
3.3
x lv
” 3.
5 x
lo”
3.8
x lo
-4
2.8x
1O
-3
1.4x
lo
4
- 1.0
-
1.2
- 3.
7 -1
8 (-
11)
- 9.
5
23.8
-
3.6
(35.
3)
(39.
1)
- -
_ -
20.5
-
5.7
- -
2 173
_ -1
5.3
- -
23.4
-
6.9
T; k
t [H
+]
$ (b
ase
cat.)
42
T;
k t
[H+]
& (b
ase
cat.)
42
S;
295
%
cis
pr
od.
51
- q
352
S 35
2
S; t
he
prod
. is
tra
ns-
C
rF2
(en)
(enH
) A
H*
.l~l;d
S*
&J
S T; (
2T),
100%
ci
s pr
od.
S S T;
100%
ci
s pr
od.
T T; <
Cl->
S;
97
% c
is p
rod.
S
328 63
52
53
54
52
55
56
53
58
DA
TA
TAB
LE
I. (C
ont.)
Com
plex
r(
m)
PH
Med
ium
k
cis
-Cr(
en)z
(OH
)Cl+
0.
1
cis-
Cr(
en)z
(NC
S)C
l+
0.1-
1.0
fran
s-C
r(en
)z(H
20)B
?+
1.4
trans
-Cr(
en)&
&+
0.1
truns
-Cr(
en)2
Clz
+ 0.
1 tru
ns-C
r(en
)&+
_
trans
-Cr(
en)&
Z+
0.1
truns
-Cr(
en)Z
Brz
+ 0.
1 rr
ans-
Cr(
en)Z
(OH
)Cl+
0.
1
0.1
cis-
Cr(
dipy
)zC
lz+
trans
-Cr(
dipy
),Cl?
+ tra
ns-C
r(tm
d)z(
HzO
)Cl*
+ tra
ns-C
r(tm
d),(H
zO)B
rZt
trans
-Cr(
tmd)
2CIz
+ Pu
ns-C
r(tm
d),B
r,+
&,a
-Cr(
trien
)Ch+
C
r(H
,O)(
tetre
nH)‘
r+
0.5
- 1.0
1.0
0.1
0.3
0.1
4 4
cis
-Cr(
ox)(
a -tr
ienH
)‘+
CrC
la(H
ZO)Z
tu
CrC
ls(H
zO)tu
z C
rC13
tu3
Cr(
acac
)a
truns
-C
r(N
H3)
* (N
CS)
.,-
truns
-Cr(
NH
3)2(
NC
S)~-
1.9
12
12
12
_ - so.1
$0
.1
2.0 1.0
2.0
0.1-
2 0.
1-2
0.1-
2
10.1
-10.
7 en
( Li
C10
4 H
ClO
,, H
N03
H
NO
a 1.
0-2.
9 (L
i,H)N
03
3.7
_ HN
Oa
1-2
(Li,H
)C10
4 9.
8-10
.8
1 en
Li
C10
4 H
NO
s
1.0
(Na,
H)C
l 3.
3-3.
9 H
NO
a
l-3
- - _ l-4
l-4
- 3-4
- l-3
2-5
9-12
HN
OZ
HN
OZ
HN
Oa
HN
O3
(Na,
H)C
104
HC
l04
HC
l04
(Li,H
)N03
H
Cl
HC
l H
Cl
HC
l04
none
M
eOH
: H
z0
(3 :
1 by
V)
_ HC
l04
HC
lO.,
(Na,
H)C
104
NaN
Oa
(Na,
H)C
104
(Na,
H)C
lO,,
(Na,
H)C
104
Na(
C10
4,0H
)
AH
* A
S’
Com
men
t Ta
ble
Ref
. N
o.
3.3
x 10
” _
- S;
96%
ci
s pr
od.
57
8.1
x lo
-’
3.0x
la
d 3.
9 x
10”
2.2
x 10
” 2.
3 x
lo+
3.3
x lti
3.
2x
lo-4
4.
6 x
1O-3
19.6
_
-11.
5 _
- -
22.6
-
4.0
22.6
-
3.8
21.8
-
1.4
_ -
_ -
ST;
98%
ci
s pr
od.
54
S 53
S
55
T 59
T;
<C
l->
60
ST
61
S; 4
% t
runs
pr
od.
53
S; 8
7 %
tra
m
prod
. 57
8.8
x lo
* (5
5”)
2.9
x 1O
-7
1.9x
lo
-’
2.9
x lo
4 1.
0x
1o-5
2.
1 x
1o-5
3.
6 x
lo4
1.9
x lO
A
3.5
x lO
A
- _
T 62
22.8
-1
1.9
23.8
-1
0 21
.1
-13.
1 23
.6
-2.2
23
.9
0.1
22.3
0.
5 20
.6
- 6.
4 22
.5
1
356
353
321
321
321
321 64
33
2
1.4x
l@
20
.1
-9
S T T T T,S
TS
TS
S; p
rod.
is
1,2
,3-C
r (H
20),(
tetre
nHz)
J+
S; p
rod.
is
Cr(
H20
)2
(tetre
nH)4
f S S S S S C
o;
<K+>
C
o;
<K+>
332
2.9
x lu
-4
19.9
-
8.1
2.4
x lo
4 14
.5
-26.
4 2.
6 x
1O-3
15
.0
-20.
1 6.
9 x
lo@
15
.1
-17.
8 8.
0x
lo-6
29
.3
16.4
1.
9x
lOA
26
.6
4.6
1.2
x lo
4 27
.9
8.0
67
65
65
65
66
71
71
6.1
x lo
-’
28.1
7
R
47
3.0
x lo
4 17
.0
-17.
6 s
68
1.2
x 1o
-3
12.3
-3
0.6
S 68
1.
5 x
1o-5
28
.5
14.7
S
69
1.6
x lo
-’
20.1
-1
3.1
S; 1
00%
ci
s pr
od.
330
1.6
x lo
-’
21.6
-
8.4
S 69
1.
7 x
1o-5
27
.7
12.6
S
70
6.2
x lo
4 16
.3
-18.
8 S
70
2.7
x lo
-’
8.4
-38
S 70
Co(
NH
3)sF
2+
Co(
NH
a)sF
’+
Co(
NH
)&C
l*+
Co(
NH
3)sC
lZ+
Co(
NH
&C
l’+
Co(
NH
3)sC
12+
Co(
NH
&C
l”
Co(
NH
3)&
1*+
Co(
NH
&C
l’+
Co(
NH
3)&
12+
Co(
NH
&B
f+
Co(
NH
3)sB
r2+
CO
(NH
~)~B
?+
1.0
O
-1.0
(N
a,H
)ClO
, 9.
7 x
10-s
-
- 0.
18-1
.2
9-10
.8
K(N
Oz,
CN
) 4.
4 x
104
-8
-47
3.0
O-O
.6
(Mg/
2,
H)C
lOd
1.1
_ _
1.0
HC
lOz,
1.
5 x
1o+2
18
.3
12.8
1.
0 o-
O.3
5 (L
i,H)C
IO,
2.0
x lo
+’
14.7
-
3.2
0.40
0.
7-1.
5 (N
a,H
)C10
4 8.
8 x
10-l
14.5
-
9.6
3.0
1.0
6.8
x 10
-l 1.
1
8.0
-0.2
5 (M
g/2,
H
)ClO
d 0.
3-1.
7 (N
a,H
)C10
4
- K
NC
S
1.0-
1.7
(Na,
H)(
ClO
,,NC
S)
HC
104
2.0-
2.2
HC
104
HzS
O4
HC
lO,
1.0
x 1o
+5
- 8.4
- 10.3
- _30
- 1.
5
1.0
10.4
0.
6
8 x
10”
- -
- 22
.9
_
5.9
x la
d 26
.6
6.7
7.2-
12.4
0.
8-4.
1 1.
1 x
10-4
24
.1
1.4x
la
d 25
.6
0.5
0.1
_ 0.12
- 0.
1 - _ 0.
002-
1.0
- - 0.1
0.01
0.1
0.4-
1.0
(Na,
H)C
104
0.3-
2.0
(Na,
H)C
104
2.0
x lo
4 -
4.2
- 7.
4
(0.6
) -
5.9
x 1o
-9
29.0
1
- no
ne
5.13
Li
C10
4 -
_ HN
O3
- no
ne
- no
ne
8.7
x lO
a 20
.7
-21.
4 8.
7 x
loa
24.4
-
8.4
1.7
x 10
” 23
.7
- 5.
5 1.
7 x
lo+
22.9
-
8.1
2.1
x lo
+ 24
.8
- 1.
3 1.
7 x
l@
23.1
2 -
7.4
6.9-
1.0
(Na,
H)N
OB
-
EtO
H
30%
(w
)
- D
XN
30
%
(w)
1.9
x lo
4 22
.6
- 9.
0 1.
1 x
10”
22.7
-
9.5
1.2
x lo
4 22
.6
- 10
.0
- ET
G
30%
(w
)
2 (K
,H)C
lO,
HN
03
1.3
x lo
-6
23.3
-
7.4
HN
O3
1.8
x lO
A
22.9
-
8.1
4.0
x 10
” 22
.9
- 6.
4 6.
3 x
lo4
24.0
-
1.8
6.5
x l@
23
.9
- 3.
0 7.
4 x
10-6
21
.8
- 8.
9 0.
002-
0.8
1.0-
6.5
(Na,
H)N
03
S R
S SF
SsF;
2T;
14
” C
ran
ge
SW
S~F ;
A S
* is
cal
cd.
from
A
S”
andA
S*
of t
he
reve
rse
reac
tion
SW
SS
F; S
OS’
- pr
obab
ly
S-bo
nded
nm
r(lb
); m
ost
likel
y Fe
-N
bond
ed
S R M;
<C10
4>,
[com
plex
] q
0.1
S R S; k
is
corr
ecte
d fo
r 80
%
Co-
O
rupt
ure
S; k
tp
& (A
H*
and
AS*
ar
e 22
.0
and
-20
atp
= 1.
0,
resp
.)
T;
<NO
a->
T; p
H
give
n is
ini
tial
pH
S K;
<CT>
T
<Clo
d->,
ac
tiv.
1
para
m.
at 2
5”
C
dAH
’/dT=
50
Cal
/mol
e X
’ K
T,
[2]
,<N
O,->
T,
[2]
; kl
DL
(at
diff
. [E
tOH
]),<
NO
s->
T, [
2] R
ate
cons
tant
de
pend
s on
[H
,O],
<NO
,->
T, [
2];
klD
l (a
t di
ff.
[ETG
])
<NO
N->
S;
(2T
, 10
” ra
nge)
S S
=
332 79
80
35
79
81
82
83
84
9 40
85
86
87
89
89
89
89
88
350
q 40
85
T,
[2]
<N
O3-
> 89
369 72
73
74
75
76
77
280 78
DA
TA
TAB
LE
I. (C
ont.)
Com
plex
p(
m)
PH
Med
ium
k
AH
+
AS”
C
omm
ent
Co(
NH
3)5B
rZ+
Co(
NH
3)5B
rZ+
Co(
NH
3)5B
r *+
Co(
NH
3)sI
Z+
Co(
NH
3)sN
3*+
Co(
NH
3)sN
CS2
+
CO
(NH
~)SN
CS’
+
_ _
MeO
H
50%
(w
)
_ _
DX
N
50%
(w
)
_ _
ETG
50
%
(w)
1.0
3 (N
H4,
H)C
lOd
0.06
44.1
64
1.85
(N
a,H
)C10
4 0.
05
2.5
HC
l04
0.00
2-O
. 1
l-2.7
H
C10
4 0.
12
0.2-
7 H
ClO
, 1.
0 ac
id
(K,H
)NO
z
Co(
NH
3)5o
x +
1.
0 1-
7 C
O(N
H~)
~OPO
~H+
1.0
54
Co(
NH
3)50
P03
Co(
Me-
NH
&C
l’+
Co(
Me-
NH
&C
l’+
Co(
Et-N
H2)
&1
Z+
1.0
0.01
-0.1
0.
01
0.01
0.12
1.0
1.0
0.1
- - 0.1
_ 0.1 1.0
-0.2
_ 1.0
1.0
2 2.0-
2.7
l-2
- - 1.0-
2.0
- 1.0-
2.0
o-7
2 - o-2
(Li,H
)C10
4
LiC
104
I (N
a,H
)NaH
POd
NaC
lO.,
(Na,
H)C
lOd
_ (Na,
H)C
lOd
(Na,
H)C
lOd
(Na,
H)C
lO.,
c N
aZSO
., H
CIO
, N
azSO
a (N
a,H
)C10
4
(K,
F>
+I
(Na,
H)C
lOd
c (N
a,H
)NaH
POA
N
aC10
4 N
aClO
., H
C10
4 H
N03
H
NO
S
Tabl
e R
ef.
No.
1.9x
lo
+ 23
.1
- 7.
1
2.6
x 10
”
3.9
x lO
A
8.3
x lo
-+’
2.1
x lo
+ 2.
8 x
1o-9
3.6
x lo
-”
1.2x
lo
* 8.
2 x
1p
22.6
-
8.5
21.9
-
9.9
19
-16
33.1
12
.8
26.8
-
7.8
30.1
-
0.7
29.6
4.
5 23
.9
-11.
1
2.4
x lo
-’
3 x
1o-5
2.
2 x
1o-7
2.7
x lO
a 1.
3 x
lo-’
4x
10+
1.5
x lo
-’
1.6~
lo
-’
4.6
x lo
+ 2.
2 x
lo+
1.2
x lo
4
7.0
x lo
-’
8.9
x 1O
-7
1.6~
lo
-’
24.3
1.
9
_ _
23.3
-1
1.2
25
-8
S 97
26
.3
- 1.
6 _
q 98
26
.4
- 3.
5 _
4 98
26
-2
S
97
25.7
-
3.0
_ q
98
32
10.7
S
97
28.4
1
S 96
18
.7
-24
S; (
2T,
13°C
ra
nge)
10
0
1.5
x lo
+ 7.
9 x
1o-9
1.5
x 1v
9 3.
7 x
1o-5
3.
3 x
lo-5
1.
6 x
lo4
24.4
-
4.9
22.7
-1
0
19.3
-2
4.8
26.2
-5
26
.8
- 6.
6
39.6
34
22
.0
- 5.
1 22
.6
- 3.
2 21
.3
- 4.
4
T, [
2];
SN2;
k d
epen
ds
on
[Hz0
1 <N
03->
T,
[2]
; k
depe
nds
on
[H,O
]; <N
Ox-
> T,
[2]
; kJ
D1;
<N
Os-
> S S S;
k =
a
+ b[
NC
S-]
<c10
4->
S,T;
(8
0~T~
97”
C)
S S; T
he
reac
tion
was
ca
rrie
d ou
t un
der
cond
i- tio
ns
whe
re
k m
ay
be
sepa
rate
d fro
m
a co
n-
com
itant
re
dox
proc
ess
S; d
4H?/
dT
= -2
0 ca
l/mol
-l de
g-’
S R R;
[21
S
89
89
89
90
91
40
46
92
93
94
99
95
101
102
103 96
95
95
105
350
350
Co@
P
r N
Hz)
sCIZ
+
0 01
H
N03
19
x10-
4 20
9
Co(
n
Bu
NH
&Z
1 2+
0
01
HN
03
20x1
04
20 8
C
o(z
Bu
NH
&C
l*+
0
01
HN
Os
37x1
o-4
16 1
u
s C
O(N
HJ)
~(H
~O
)OP
O~
&~
+
10 8
H
CIO
, 1
1x1o
-6
24 4
C
LS
CO
(NH
&H
~O
)OP
O~
H~
~+
0
66-5
7
HC
IO,
36x1
0”
24 9
tran
s C
o(N
H&
&+
01
tr
am
CO
(NH
~)~
CI~
+
10
frun
s C
o(N
H3)
.,(N
CS
)C1+
05
tr
un
s C
o(N
H3)
4(N
02)C
lf
01
tram
C
O(N
H~
)~(N
O~
)BI+
01
C
o(N
H&
(NO
&N
CS
_
Co(
NH
&(O
NO
)z,-
25
tr
am
Co(
py),
(HzO
)C1*
+
-
tran
s C
o(py
),C
lz+
_
fru
ns
Co(
py),
C12
+
trun
s C
o(py
),C
lz+
tr
un
s C
o@
p~&
Cl~
+
tram
C
o(y
~ic
)~C
l~+
C
o(en
)(N
H3)
(NO
z)N
CS
C
IS C
o(en
)(N
H3)
2C12
+
fran
s C
o(en
)(N
H3)
2C12
+
cu
Co(
en)2
(0H
2)23
+
us
Co(
en),
(NH
3)(0
H2)
” C
IS C
o(en
),(H
ZO
)OP
03H
33+
C
IS C
o(en
X(N
H:,)
OP
OgH
33’
CIS
Co(
en)2
(HzO
)C1Z
+
cts
Co(
enh
(NH
3)C
lZ+
C
IS C
o(en
),(N
H:,)
Cl’+
czs
Co(
en),
(NH
,)C
I’+
1 a
s C
o(en
),(N
H3)
B?+
d
I ct
s C
o(en
)z(N
H~
)ON
022f
u
s C
o(en
)2(N
HzO
H)C
12C
cu
C
o(en
)z(N
H20
H)B
rZ+
cz
s C
o(en
),(M
eNH
Z)C
IZf
CIS
Co(
en)z
(MeN
H2)
C1Z
+
cu
Co(
en)z
(MeN
H2)
Bf+
HN
03
HC
l04
HN
03
HN
OZ
H
N03
-
- HC
IO‘,
none
su
e 10
% (
w)
1 8
x 1O
-3
1 5
x 1o
-3
36x1
0A
27x1
0-*
7 2
x 1o
-2
8 2
x lO
-5
17x1
0-4
_ 98~
10~
22 0
25
7
176
19 2
25
8
16 0
25
4
317
- 55
-
56
-183
-
40
- 78
(0 1
) -
24
3 -
67
1 93
-22
1 -
24 9
_ -
ET
G
lo-I
O%
(w
) (9
5 x
10-
6)
30 4
20
5
- _ - - 01
01
08
0 01
40
37
- - m
dep
ofp
1-92
-
l-92
-
l-92
-
- _ H
NO
Z
HN
OZ
0
1-O
5
(Na
H)C
104
HC
104
HC
l04
HC
104
2-3
HN
OX
_
non
e 0
3-2
(Na
H)(
N09
C
lO4)
84xl
F6
25x1
0-5
1 5
x 1o
-5
29x1
0-’
23~
10~
22
x104
75
x10-
6 11
x10-
6 5x
lo
- 3
6 x
lo-’
16~
10~
37
x10-
’ (7
0 x
10-
9)
- - 22 3
28 8
- 24
9
27
1
24 9
23
2
- - - - 48
- -
1.5
_ - 83
-
28
- - 43
-1
8
_ 0 17
0
17
0 50
0
50
01
HC
IO,
HC
104
HC
104
HC
IO.,
non
e H
NO
a
5 5
x 1o
-7
22 6
-1
14
16x1
0”
22 5
-
96
94x1
0+
23 5
-2
7
50x1
0+
19 7
-1
67
2 1x
1o-5
19
6 -1
4 2
2 3
x lo
+
24 4
-
71
35x1
0-7
23 9
-8
S S S R
R
350
350
350 79
79
S
T S
45
f
10%
tr
am
prod
S
S
10
0%
tram
pr
od
S
100%
tr
am
prod
_ S
K
S
<C
l->
T
[2
] k
J [W
C]
? bu
t A
H*
and
AS*
ar
e es
sen
tral
ly c
onst
nt
up
to
40%
su
e <
CT
>
T
[21
130
154
346
333
333
174
176
155
156
158
T
T
T
- S
S
M
M
R
R
100%
C
D p
rod
T
<S
O4’
->
T
<C
D->
-
[2]
act
para
m
mde
p of
p
pH
pres
ence
of
EtO
H
GL
C
ET
G
159
159
159
174
130
130
125
106 79
30
2 12
7 87
108
T
S
(2T
) S
(2
T)
T
<N
O,-
>
T
<N
03->
T
<
N03
->
T
[2]
k A
H?a
nd
AS*
ar
e n
ot s
ensi
tive
to
add
ed E
TG
u
p to
40
%by
w
q 10
7 10
9 10
9 11
9 11
1 10
7 11
0
4 6
x lo
-’ 26
3
07
T
cN03
->
111
DA
TA
TAB
LE
I. (C
ont.)
Com
plex
P
(m)
PH
Med
ium
k
AH
+
AS’
C
omm
ent
ci.s-
Co(
en),(
EtN
HZ)
B?
cis-
Co(
en)z
(n-P
rNH
z)C
l’+
cis-
Co(
en),(
n-Pr
NH
z)B
r*+
cis-
Co(
en),(
i-PrN
HZ)
Cl”
ci
s-C
o(en
),(i-P
rNH
Z)B
? ci
s -C
o(en
)z(A
llNH
Z)C
l*f
cis-
Co(
en)z
(AllN
Hz)
CIZ
+
-
Tabl
e R
ef.
No.
cis-
Co(
en)2
(A11
NH
z)B
?+
cis
-Co(
enX
(P
r-2
-yny
INH
2)C
lZ+
cis-
Co(
en)z
(Pr-
2-yn
ylN
Hz)
B?’
ci
s-C
o(en
),(C
H20
HC
HzN
Hz)
C12
+
- - _ - 0.1
- - 0.1
0.1
0.1
HC
lO.,
8.1
x lo
-6
25 .S
-5
H
CI0
4 4.
2 X
lO
-7
25.5
-
2.1
HC
l04
7.3
x lo
-’
25.7
-
0.4
none
5.
6 x
lo_7
22
.5
-11.
7 no
ne
1.3
x lo
+ 22
.2
-11.
0
cis-
Co(
en)Z
(CH
aOC
H,C
H2C
H2N
Hz)
C12
+ no
ne
cis-
Co(
en),(
CH
3CH
ClC
H2N
H2)
CIz
C
0.1
HC
l04
cis-
Co(
en)~
(CH
2CIC
H2C
H,N
H2)
C12
+ 0.
1 H
C10
4 as
-Co(
en),(
CH
20H
(CH
2)aN
H2)
Cl
2+
none
ci
.s-C
o(en
)z(C
H20
H(C
H2)
4NH
z)C
lZC
no
ne
cis-
Co(
en),(
CH
ZOH
(CH
&N
H2)
C12
’ no
ne
cis-
Co(
en)2
(@-C
HzN
H2)
CIZ
+ 0.
05
HN
Oa
4.7-
5.7
,/ (N
a,H
)OC
OC
Ha
5.0
x lo
-’
\ (N
a,H
)OC
OH
no
ne
1.5
x lo
-’
3 H
N03
3.
4 x
lo-’
-
none
no
ne
none
no
ne
none
H
NO
a
none
5.
6 x
lo-’
26
.8
2.8
no
ne
1.2
x lo
-’
25.4
-
5.0
none
3.
1 x
lo-’
26
.6
0.9
none
1.
7 x
lOA
21
.8
-11.
8
2.9
X l
o-’
3.2
x 10
” 1.
8 x
10d
1.2
x lo
4 7.
3 x
10”
2.0
x lo
-’
3.3
x lo
-’
3.5
x lo
-’
6.5
x IO
-’
9.8
X lo
4 1.
3 x
lo-’
3.
7 x
lo-’
4.
8 X
lo-’
4.
8 X
lo-’
1.
8 X
lo-’
22.6
-1
1
26.1
-
2.2
24.3
-
6.5
27.5
3.
8 24
.6
- 5.
7 22
.9
- 8.
0 24
.3
- 4.
1 22
.9
- 5.
2
25.4
-
4.0
23.3
-1
8 (-
10)
23.4
-
9.6
22.2
-1
2.4
25.5
-
5.1
25.8
-
3.6
23.7
-
8.5
23.4
-
9.0
23.4
-
9.0
2.4.
5 -1
5 (-
7.2)
T;
[21
T; <
NO
,->
T; A
H*
is i
nsen
sitiv
e to
+ 40
% w
DX
N
and
-+60
%ET
G;A
S*
Iby
a fa
ctor
of
-2
in b
oth
case
s T;
<NO
a->
S; <
NO
,->
T ; <
NO
,->
T;<N
O,->
T;
<N
O,->
T; <
NO
,->
T;(2
]; A
ct.
par.
are
unaf
fect
ed
by+
40%
(w
) ET
G
and-
+ 20
%
(w)
DX
N
T; <
NO
,->
T; <
NO
a->
T; <
ClO
4->
T;
100%
ci
s pr
od.;
<NO
,->
T T T T; <
NO
,->
T;
100%
ci
s pr
od.;
<NO
,- >
T;
100%
ci
s pr
od.;
<NO
,->
T; <
N03
->
T T S,T;
<N
O,->
S,
T;
<NO
,->
S,T;
<N
O,->
T;
[2]
; A
ct.
par.
are
unch
ange
d by
add
ition
of
ETG
(4
0%
by w
.) an
d D
XN
(2
0%
by w
.)
112
107
113
111
114
111
114
111
115
110
111
115
111
116
117
117
117
118
116
116
118
117
117
347
341
347
110
DA
TA
TAB
LE
I. (C
ont.)
Com
plex
p(
m)
PH
Med
ium
k
AH
+
AS+
C
omm
ent
Tabl
e R
ef.
No.
trans
-Co(
en),(
NO
z)C
lf 0.
1 lr
ans-
Co(
en),(
NO
$I+
0.
1 tr
ans-
Co(
en)2
(N02
)C1+
0.
1 tr
ans
-Co(
en)2
(N02
)C1+
0.
1
trans
-Co(
en)2
(NO
z)C
lf tra
ns-C
o(en
)Z(N
02)B
r+
tran
s-C
o(en
),_(N
CS)
Cl+
tra
ns-C
o(en
),(N
CS)
CI+
tra
ns-C
o(en
),(N
CS)
Cl+
tr
am-C
o(en
),(N
CSj
Cl+
tr
ans-
Co(
en),(
NC
S)C
l+
tran
s-C
o(en
)2(N
CS)
Br+
0.
007
Pan
s-C
o(en
),(N
CS)
Br+
0.
01
0.01
truns
-Co(
en),(
NC
S)B
r+
0.01
truns
-Co(
enh(
OH
),+
0.8
truns
-Co(
en),(
CH
BC
OO
)(O
HC
OC
H3)
2’
2.0
truns
-Co(
en),(
CH
BC
OO
)CIC
0.
012
truns
-Co(
en),(
@-C
OO
)Cl+
0.
012
Co(
en)2
(H20
)C1Z
+ 0.
1
truns
-Co(
Me-
enhC
l,+
truns
-Co(
Et-e
nhC
l*+
truns
-Co(
en)(
tn)C
h+
truns
-Co(
n-Pr
-en)
zC1z
+ lru
ns-C
o(pn
)2C
12+
truns
-Co(
pn)2
(0H
)Cl+
tr
uns
-Co&
l -b
nh&
+ tr
uns-
Co(
m-b
n)$&
+
trans
-C~(
i-bn)
~Cl~
+ C
o(i-b
n),(c
ytam
)Clz
f
cis
-Co(
phen
)2C
12c
0.1
0.1
0.10
0.
10
0.10
0.1
0.00
25
0.10
0.
01
_ 0.1
- 0.00
7 -
- - - - - _ -
- 8.
9 X
1V
19
.6
- 6.
7 su
e 40
%
(w)
4.9
X lO
A
19.3
-
8.9
ETG
40
%
(w)
MeO
H
(30%
by w
.) A
ceto
ne
30%
(w
) - H
CIO
, ET
G
40%
(w
) su
e 40
%
(w)
GLC
40
%
(w)
EtO
H
30%
(w
)
4.4
X I
O-4
19
.0
-10.
1 4.
5 X
l@
18.7
-1
1.1
4.4
X 1
0”
18.8
-1
0.8
5.1
x 10
-3
21.4
-
1 4.
5 X
10-
a 29
.8
7.8
2.4
X l
p 29
.4
5 2.
6 X
lp
29.5
6
2.3
X 1
0”
29.4
5
1.6
X 1
F”
29.1
3
HC
IO,
1 H
N03
Et
OH
40
%
(w)
c H
N03
ET
G
40%
(w
)
( H
NO
X
GLC
40
%
(w)
13.5
-13.
9 N
a(C
104,
0H)
-0.3
-l (N
a,H
)C10
4 H
ClO
, H
ClO
, 4.
7 (
(Na,
H)O
CO
CH
, (N
a,H
)OC
OH
H
N03
HN
O3
HN
03
HN
O,
HN
O3
7-8.
7 N
aOH
H
NO
3 H
NO
, H
N4
HC
lO,
- no
ne
6.8
X 1
o-s
23.1
2.4
X lo
-’
29.5
10
.1
1.4
X lo
-’
28.0
4
1.8
x lo
-’
27.7
4
1.6
X l
o-’
28.5
6
2.3X
lo
-6
30.4
20
(1
8)
1.6
x 10
” 23
.0
1 3.
1 X
10”
26
.8
6.7
1.2X
10
-6
29.3
13
.2
2.7
X lO
-’ 26
.9
11
1.6
X l
o-’
9.6
X 1
0-’
4.3
x 10
-4
1.2
x 10
” 6.
1 x
10-s
1.
3 x
10”
1.5X
lo
” 4.
2 X
lF3
2.
2 x
lo-3
1.
2 X
lO
A
26.5
8.
4 27
.5
15.4
25
.5
11.6
26
.5
12.4
27
.5
14.6
- 25
.5
23.5
25
.5
23.4
_
9.5
9.4
14.8
-
0.5
(2.0
) 0
- _
I k is
a f
unct
ion
of
- [H
z01
but
not
of D
. - - I
S T; [
2]
logk
de
crea
ses
T; 1
21
linea
rly
with
T;
i2j
I
T; [
2]
I (l/
D)
and
is
inse
nsiti
ve
to t
he
natu
re
of t
he
orga
nic
com
- po
nent
S
; 5 5
% t
ram
pr
od.
T; [
2],
logk
de
crea
ses
linea
rly
with
(l/
D)
T; (
21,
logk
de
crea
ses
linea
rly
with
(l/
D)
T;
[2]
M
S,&
; 75
% t
rans
pro
d.
S,T;
80
%
cis
prod
.
ST
T;
[2],k
tpH
f
125
329
323
323
112
ST
161
S,T
161
S 16
1 T
161
S,T
161
T 13
6
S,T
161
S 16
1 S
161
S 12
3
T, <
Cl->
15
3
142
142
142
142
142
q 16
7 16
5 14
0 14
0 14
0 14
0
139
144
144
144
trans
-Co(
dipy
)z(N
Ozh
+ tra
ns
-Co(
DH
)2C
12-
trans
-CO
MB
ED-
trans
-Co(
DH
k(N
CSk
- tru
ns-C
O(D
H)~
(SO
~)C
I~
fran
s-C
0(D
H)~
(S0~
)B?-
tru
ns-C
O(D
H)~
(SO
~)I*
- C
o(ac
ac)z
(H20
)ON
0 C
o(C
pdox
H)(
Cpd
oxH
z)(N
02)(
N02
H)+
C
o(C
pdox
H)(
Cpd
oxH
Z)(N
Oz)
z C
o(di
en)(
NO
&N
CS
E-C
o(di
en)(
en)C
l’+
o -C
o(di
en)(
en)C
l*+
w-C
o(di
en)(
en)B
? w
-C
o(di
en)(
en)I
’+
fran
s-C
o(da
n)C
lz’
cis-
Co(
tren)
(H,O
)Cl’+
ci
s-C
o(tre
n)(H
zO)B
rZ+
cis-
Co(
tren)
F*+
cis-
Co(
tren)
CIZ
+ ci
s-C
o(tre
n)B
r2+
D,a
<is-
Co(
trien
)(H
zO)C
12+
,8-c
is-C
o(tri
en)(
H20
)C12
+ (s
low
is
omer
) @
is-C
o(tri
en)(
HzO
)Clz
+ (f
ast
isom
er)
p-ci
s -C
o(tri
en)(
HzO
)CIZ
+ ci
s-C
o(tri
en)(
NH
3)C
12+
a <i
s-C
o(tri
en)C
IZ+
D-a
-&s-
Co(
trien
)Clz
f ci
s-C
o(tri
en)C
12+
p-ci
s-C
o(tri
en&
+ D
-/Lci
s-C
o(tri
en)C
lz+
Da-
&-C
o(tri
en)(
OH
)Cl+
tra
ns-C
o(tri
en)(
H20
)Clz
+ fr
ans-
SS-C
o(tri
en)C
12+
/3-c
is-(
RR
,SS)
-Co(
2,3,
2-te
t)Clz
+
2.5
- _ _ - - - 0.5
1.0
1.0
_ 0.01
0.
01
0.01
0.
01
0.10
1.
0 0.
1 _ 0.
1 0.
1 0.
1 0.
1
0.1
0.01
- 0.
01
51
(Na,
H)N
4 -
none
-
none
_
- -
- -
- -
none
-
NaC
104
- (N
a,H
)(C
KLN
O~)
_
(Na,
H)(
CK
LNO
~)
_ - H
CIO
., H
ClO
., H
C10
4 H
C10
4 H
N03
H
ClO
, H
ClO
z,
- no
ne
HC
104
HC
104
l-3
(Na,
H)C
104
l-3
(Na,
H)C
lO.,
l-3
(Na,
H)C
104
HC
l04
- no
ne
HC
lO,
1.3
x lo
-’
2.7
x lo
-4
3.8
x 1K
” 1.
2 x
lo+
(6.0
x
lo-‘
) (8
.4
x lo
-‘)
(9.8
x
lo-‘
) 1.
4 x
lOA
3.
6x
l@
1.1
x lo
-6
3.1
x 1p
3.
3 x
lo+
1.9
x lo
-’
2.4
x lo
-’
1.8
x lo
-’
3 x
lo-3
2.
4 x
lOA
1.
6 x
lOA
9.
0 x
lo4
3.0
x 1o
-3
2.8
x lo
-’
5.2
x lo
-’
2.0x
lo
+
23.5
-1
1.2
23.3
3.
6 23
.9
6.0
31.6
12
.9
23.5
-
8.3
21.5
-
14.2
19
.5
-20.
6 26
.2
12.5
18
.8
-10.
9 25
.4
- 0.
2 26
.9
6.5
24.4
-5
23
.4
-9
25.4
-2
28
.4
7 23
.5
8.8
21.6
-1
1 -
-
22.3
-
6.5
17.3
-1
0.4
15.1
-1
5.0
23.5
-
8.4
26.4
3.
9
8.2
x lO
-’ _
-
0.00
1-1.
0 H
ClO
., 0.
1 H
NO
Z 0.
01
HC
l04
0.00
2-l
o-3
(Na,
H)C
lOd
0.1
l-3
(Na,
H)C
lO.,
0.1
HC
lO.,
0.1
HC
104
0.00
5-l
HN
09
2.4
x 1O
A
1.7
x lo
-’
1.5
x l@
1.
6x
lo4
1.5
x 1o
A
1.5
x l@
1.
5 x
1o-3
3.
8 x
lo-3
2.
0 x
lo+
3.2
x 1O
-3
1.1
x lo
-3
_ _
24.9
-
5.8
- -
20.9
-
5.8
_ -
_ -
20.5
-
2.7
18.8
-
6.5
26.4
3.
9 25
.4
15.3
22
.3
2 (3
)
truns
-R,S
-Co(
2,3,
2-te
t)C&
+ 0.
016
HN
03
1.5
x lo
+ 24
.3
1 tra
ns-R
R,S
S-C
o(2,
3,2-
tet)C
lz+
0.01
4 H
C10
4 2.
9 x
lo-’
25
.9
12
cis
-Co(
cycl
am)C
lz+
1.6x
lo
-’
18.3
-
5.4
trans
-Co(
cycl
am)C
IZ+
trans
-Co(
cycl
am)(
OH
)Cl+
tra
ns-C
o(cy
clam
)(N
C)C
l+
trans
-Co(
cycl
am)(
N02
)Cl+
0.51
0.01
0.
10
0.01
0 0.
010
2.0
i N
a(N
O&
l) H
CIO
., H
N03
7.
0-11
.8
buff
ers
HN
OJ
HN
Os
1.1
x la
d 24
.3
- 4.
3 1.
2 x
lo-z
18
.8
- 4.
2 4.
8 x
lo-’
23
.5
-9
4.3
x l@
20
.6
-9
S P; <
H+>
P;
(2T
), <H
+>
C,G
,T;
<H+>
K
PH
, T
K
pH,
T K
, PH
, T
S C;
colo
rim.
C;
colo
rim.
- S S S S S S SK
s;
<c10
,->
S,K
S,
K
SAP;
SJ
LP,
S&P,
1
Ret
ent
of c
is
conf
. an
d op
t. ac
t.
169
171
171
173
172
172
172
175
345
345
174
123
123
123
123
161
295
150
277
355
150
147
147
147
S,K
T;
[3]
, <C
lOa-
> S,
K
SAP,
S S,
K
SKP,
S&
P,
S,K
SK
S;
B
(RR
,SS)
co
nf.
pres
umed
148 87
14
8 14
7 13
0 14
8 14
7 14
7 14
7 14
7 15
2
S; 1
00%
tr
ans-
R,S
pr
od.
S ; 5
0 +
20 %
tra
ns -R
R,S
S pr
od.
S; 1
00%
ci
s pr
od.
152
152
151
S; 1
00%
tr
ans
prod
. S;
100
%
tran
s pr
od.
S; 1
00%
tr
ams
prod
. S:
100
%
tram
m
od.
168
168
252
I 25
2
DA
TA
T
AB
LE
I.
(C
ont.
)
Com
plex
_
tran
s-C
o(cy
clam
)(N
02)B
r+
0.01
0 tr
ans-
Co(
cycl
am)(
NC
S)C
l+
0.01
0 tr
ans-
Co(
rac
-L’)(
HzO
)C12
+
0.01
0 tr
am -
Co(
rac
-L’)C
12+
0.
010
tram
-C
o(L
)C12
+
0.01
0 a-
Co(
tetr
en)C
l’+
1.0
CO
(CN
)~O
H~
*-
1.0
Co(
CN
)J-
CO
(CN
)SN
~~
- C
o(C
N),
NC
S3-
C
o(C
N)s
OS
zOz’
M
o(N
CS
&~
- M
oC&
,-
1.0
1.0
1.0
1 .o
Ru
(NH
&C
l*+
Ru
(NH
&B
f+
Ru
(NH
&‘+
cis-
Ru
(NH
3)4C
l,+
cis-
Ru
(en
)z(H
ZO
)C12
t
cis-
Ru
(en
),(H
ZO
)B?’
cis-
Ru
(en
)Z(H
zO)I
Z+
cis-
Ru
(en
)#.Z
l,+
cis-
Ru
(en
)zB
r2+
cis-
Ru
(en
)&+
cis-
Ru
(-pn
)&12
’
cis
-Ru
(a -
trie
n)(
HzO
)C1*
+
cis-
Ru(
a -t
rien
)Clz
t
0.1
0.1
Ru
(HzO
)Cl5
’- _
Ru
Cb3
- 1.
0 R
uC
le3-
6.
0
0.1
0.1
0.1 0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
PH
M
ediu
m
HN
Oa
HN
03
HN
Oa
HN
Oa
HN
Oa
HC
l04
6.4
N a
ClO
d
- N
aC10
4 6.
0-13
.0
Na(
ClO
+O
H)
13
Na(
ClO
,,,O
H)
13.7
-14.
0 K
(NO
a,O
H)
- N
CS
- 3.
24.5
(
KH
Ph
thal
ate
HzS
04
or K
OH
CH&S
O,H
CH@
SO,H
CH,@
SO,t’
CH,@
SO,H
CH,@
SO,H
CH@
SO,H
CH@
SO,H
cH@
SO,H
CH,@
SO,H
C tI@
SO,H
CH@
SO,H
CH,@
SO,H
CH,+
SO,H
- - H
CI
HC
l
k 5.5
x lo
4 3.
2 X
lo4
3.
4 x
lOA
4.
2 x
lO-3
9.
3 x
lOA
4.
6 x
lOa
1.3
x 1F
(40”
) 6.
2 x
lo-’
5.4x
l@
2.
8 x
lo4
2.6
x lo
+
3.5
x lo
+
1.3
x lO
A
(0”)
7.1
x lo
-’
8.7
x lo
-’
2.5
x lO
-’
7.8
x lC
r+
1.7
x lo
-5
1.4
x lo
-5
2.7
x 10
”
3.8
X 1
O-5
3.2
x lo
-’
1.0x
lo
-s
3.8
x 1o
-5
2.0
x lO
A
5.85
x l
o4
(3.5
x 1
0”)
6.7
x lo
-*
1.8
x 1K
3
AH
* A
S*
(21.
0)
-3
24.2
-1
1 39
.5
58
28.3
-
25.6
13
26
.4
-5
- _
29.7
12
.5
27.3
-
0.6
31.1
11
.5
21.6
-2
1.1
21.3
-1
1.8
- -
22.6
-1
0.8
22.6
-
10.5
23.9
-
8.5
21.8
-
8.8
20.1
-1
3.0
21.8
-
7.7
24.4
2.
4
19.9
-1
2.0
20.5
-1
0.3
22.1
-
7.2
18.2
-1
7.8
_ _
18.1
-
12.6
21.4
2
_ -
24.6
12
Com
men
t T
able
R
ef.
No.
S 34
8 S
346
S,T
36
0
ST
36
0
S,T
36
0
S,T
12
4 M
17
7
S 17
8
S; (
2-O
17
7
S; W
) 17
7 S
17
9 R
47
S
35
4
S S S S S S S S S S S s R
R
180
181
181
181
181
181
181
181
181
181
181
181
181
q 18
2 q
187
182
RuC
L,-
Rh(
H,0
)b3+
R
h(N
H,)s
OH
,3+
Rh(
NH
3)50
H,3
+ R
h(N
Hs)
5N3H
3+
Rh(
NH
&C
l’+
Rh(
NH
&C
I’+
Rh(
NH
&C
l*+
Rh(
NH
&C
l’+
Rh(
NH
s)sB
?+
Rh(
NH
s)sB
?+
Rh(
NH
x)sB
?+
Rh(
NH
3)JZ
+ R
h(N
HJ)
$+
Rh(
NH
&I’
+ R
h(N
H3)
50N
Oz*
+ R
h(N
H,)s
OC
OC
F,*’
R
h(N
H3)
50S0
3+
truns
-Rh(
NH
&C
l,+
trans
-Rh(
en)Z
Cl*
+ tr
ams -
Rh(
en)z
Clz
+ tra
ns-R
h(en
)zC
lz+
fran
s-R
h(en
)ZB
rCl+
tram
- R
h(en
)JC
l+
trans
-Rh(
en)z
IC1+
truns
-Rh(
en)&
Br+
trans
-Rh(
enhB
rz+
trans
-Rh(
en)z
Br*
+
trans
-Rh(
enkI
Br’
trans
-Rh(
en)&
+
trans
-Rh(
en)z
Iz
+
Rh(
DH
)*(S
03H
)Br+
R
h(D
Hk(
SOaH
)I+
Rh(
H20
)ClS
Z-
RhC
&*
II(N
H&
OH
~~+
Ir(N
H&
Zl*+
Ir
(NH
,),B
f+
_ 20.7
(A
1/3,
H)C
I04
2.0-
1.3
(Na,
H)C
104
2 H
ClO
, H
&L
none
HC
104
NaC
104
N&
Br
none
N
aC10
4 N
&C
l no
ne
NaC
104
N&
Cl
2 (N
a,H
)C10
4 2-
l (N
a,H
)C10
4 o-
2 (N
a,H
)C10
4 -
NaB
r or
NaI
-
- none
N
aI
(8 X
10-
2)
3.2
X lo
+ 1.
0 x
1o-5
8.
4 x
lo+
2.0
X lO
A
1.42
X
lo-
’
4.83
X
lo+
1.5
x lO
-’
3.8
X 1
LP
4.87
X
lo4
6.
30
X l
o+
3.40
X
loa
8.31
X
1O
-9
1.95
X
1P
6.2
x lo
-’
1.2X
l@
2.
0 X
10-
7 1.
6X
l@
1.3
X lo
-’
6.4
X lo
4 _ 5.
4 x
lo+
NaB
r 1.
7 X
lO-’
- - N
aI
1.0X
lo
” 4.
8 X
10-
’
27
33
23.9
24
.6
26.7
20
.4
23.8
22.2
24.2
23
.5
24.4
24
.6
25.4
26
.7
26.2
23
.3
25
21.4
24
.1
23.8
24
.5
24.7
2z
18
- 1 0.
8 5.
0 -2
1.4
-12.
2
-15.
3
-11.
1 -1
3.3
- 9.
6 -
9.9
- 10
.3
- 4.
2 -
7.8
-3
-6
-13.
3 -
9.2
-13
q 18
2 P
183
G‘
184
%
318
; 35
a”
F 18
8 8
185
2 18
6 $ _.
187
189
G
186
8 $ 18
7 3
188
&
186
s 18
7 2
160
fi 97
D
10
2 33
6 19
1 19
2 19
0
12
0.5
0.25
8.
1-9.
2
M
M
M;
[com
pl.]
= 0.
040M
S R
; <C
l->
S T S R;
<Bf>
T S R
; <I
->
T S S S S S S R S ; 1
00 %
tra
m
prod
. ;
k in
sens
itive
to
p S;
100
%
trans
pr
od.;
k in
sens
itive
to
p S S;
100
%
tram
pr
od.;
k in
sens
itive
to
,u
S; 1
00%
tr
am
prod
.; k
inse
nsiti
ve
top
S S; 1
00%
tr
ans
prod
.; k
inse
nsiti
ve
top
S
0.01
~.02
5
0.1
0.2
0.1
0.2
0.1
0.2
1.0
0.1
1.0
0.05
-0.1
0.1
-9
0.20
23
.2
-11.
7
14.0
-3
1.8
21.1
-
7.5
190
191
190
0.20
NaC
l 8.
3 X
1K
9 27
.6
-3
190
0.20
5.6
X lo
-’
20.0
1.
8 X
lo-’
25
.2
-22.
0 -5
19
1 19
0
- 0.1-
0.5
- - N
aI
4.6
X 1
O-5
16
.1
191
-26.
3 (-
24.3
) -3
N
aBr
2.1
X lo
-5
23.1
S;
100
%
tran
s pr
od.;
k in
sens
itive
to
,u
S S; 1
00%
tr
ans
prod
.; k
inse
nsiti
ve
top
T T S S M
R;
<CT>
R
; <B
r->
190
0.20
3.5
X 1
0”
26.2
4.
3 X
1cP
25
.1
191
190
4.4 1
- 0.20
- -
- 1 N
aCl
or N
aBr
OI
NaC
N
HN
03
HN
03
H(C
lO&
l) H
(ClO
.,,C
l) 0.
3-2.
0 (N
a,H
)C10
4 no
ne
none
1.2
X 1
O-s
13
.7
-35.
1 3.
0 X
1O
-5
12.2
-3
8.3
3.9
X 1
o-5
25.2
5.
8 1.
8X
10-3
24
.5
11.1
6.
5 X
lO+
28.2
3.
0 1.
1 x
lo+
22.4
-2
4.3
1.1
X l
o+
22.5
-2
4.1
349
349
193
194
195
188
192
2’
0.05
0.
05
4.0
4.0
0.96
DA
TA
TAB
LE
I. (C
ont.)
2
Com
plex
P(
m)
PH
Med
ium
k
AH
* A
S*
Com
men
t Ta
ble
Ref
. N
o.
Ir(N
H,)$
+ Ir
(NH
&O
NO
,‘+
Ir(N
H&
0CO
CFj
2+
trans
-Ir(
en)Z
Cl,+
ba
ns-I
r(en
),BrC
I+
trans
-Ir(
en),I
Cl+
0.
5 tru
ns-I
r(en
)zB
rz+
0.5
frun
s-Ir
(enX
IBr+
0.
5 tru
ns-lr
(en)
z12+
0.
5
Ir(H
20X
C13
Ir
(H,O
)sB
r, tru
ns
-Ir(
H20
XC
L-
Ir(H
20)K
L-
Ir(H
20)z
Br4
- Ir
(HzO
)C15
2-
Ir(H
20)C
152-
Ir
Q-
IrC
&-
IrC
163-
- 3.8
- - 3.75
- _ 1.
0 2.
2 1.0
0.1
0.5
0.5
none
2
(Na,
H)C
104
l-2
(Na,
H)C
lO.+
N
a(C
IO,,X
) N
a(C
lO,,B
r)
Na(
ClO
,.X)
Na(
C10
4,X
) N
a(C
104.
X)
Na(
C10
4,X
)
-3
-3
90
-3
-3
<o
-3
-3
0
&S
O4
(4.7
x
10-9
) 28
.9
Hz.
%
(7.3
x
lo-“
) 33
.0
(Na,
H)C
104
8 x
10-q
29
.9
HzS
O.,
(1.4
x
10d)
30
.1
HzS
O4
(6.1
x
104)
28
.8
(Na,
H)C
104
2.9
x lo
-’
28.8
H
zSO
., (2
.5
x 10
-7)
28.8
H
zSO
4 (4
.0
x 10
-5)
24.9
H
C10
4 2.
5 x
10-s
27
.4
(Na,
H)C
104
1.0
x 1o
-5
29.8
1.9
x 1o
-‘o
25.6
6.
9 x
1cP
26.1
5.
1 x
lo+
24
1.4
x 1o
P 29
.2
4.4
x 1o
P 27
.1
1.5
x lo
4 25
.3
8.5
x 1o
-‘o
27.2
6.
3 x
1O-9
27
.1
2.0
x 1o
-9
28.7
-17.
3 -4
-1
6 -6
-9
(-
10
.4)
- 4
(-9.
4)
-9
-5
-3
(-2.
1) 0.3
5.8
4.7
6.5
5.1
8.2
7.9
4.9
12.3
18
.6
R;
<I->
S S S.
T;
X-
= I-
, N
3-,B
r-
S,T
S,T;
X
- =
I-,
Br-
196
S,T;
X
- =
I-J-
19
6 &
T;
X-
= I-
, C
l- 19
6 S,
T;
X-
= C
T,
Bf
196
R
R
S R
R
S,T
R
R
R
S
188
160 91
19
6 19
6
197
197
198
197
197
199
197
197
200
201
DA
TA
TAB
LE
II.
Solv
olys
is
(non
-aqu
eous
so
lven
ts).
Com
plex
.
V(D
MS0
)5(S
SA)3
+ V
(DM
S0)5
(NC
S)2+
P(M
)
- 0.15
AH
* A
S*
: PH
M
ediu
m
k C
omm
ents
Ta
ble
2 R
ef.
s
No.
r, h Q
-
DM
SO
1.7x
1o-3
-
- S.
20
2 D
MSO
1.
5 9
_ -
- SW
20
2 a
NaC
104
8.
V(D
MSO
),(di
py)3
+ C
r(N
H3)
e3+
cis-
Cr(
ox),(
OH
&-
cis-
Cr(
ox~(
DM
SO)(
OH
2)-
Cr(
NH
&(N
CS)
+-
Cr(
NH
3)z(
NC
S),-
Cr(
NC
S)63
-
cis-
Cr(
en),B
rz+
cis-
Cr(
enb(
DM
SO)B
? tra
m-C
r(en
)zB
r2+
cis-
Co(
en),C
l,+
cis
-Co(
en),C
IBr+
ci
s-C
o(en
),Cl(D
MF)
‘+
cis-
Co(
enhC
l(DM
F)‘+
ci
s-C
o(en
),Cl(D
MSO
)Z+
cis
-Co(
en)lC
I(D
MSO
-&)2
f ci
s-C
o(en
kCl(D
MA
)‘+
cis
-Co(
en),C
l(DM
A)‘
+ ci
s-C
o(tre
n)B
r,+
cb -
Co(
tren)
Brz
+ ci
s-C
o(tre
n)B
rz+
cis
-Co(
tren)
BrZ
+ ba
ns
-Co(
en)2
Clz
+ tra
m-C
o(en
)#&
+
trans
-Co(
en)2
(NO
z)C
1+
tram
-Co(
en)2
(N02
)Brf
- _ _ - - _ 0.1
- - - - - -0
-0
-0
- -0
-0
- - - - - 0.1
-0
-0
-0
- o-1.
5
0.1
0.1
- - - _
- - _ - - _ _ _ _ _ - _ - - - _ - - - - _ - _ - _ - - - _ - _ - - - -
DM
SO
liq N
H3
DM
SO
DM
SO
MeO
H
I M
eOH
: M
eNO
z 1
: l(v
)
t M
eOH
N
aC10
4 D
MSO
D
MSO
D
MSO
D
MF
DM
F D
MSO
D
MA
D
MA
D
MF
DM
SO
DM
F FA
D
MSO
D
MF
NM
F D
MF
c D
MF
KN
CS
bMS0
D
MF
DM
F FA
1 TM
S K
CN
S
c D
MF
KN
CS
1 D
MF
KN
CS
CH
,CO
OH
CH
,CO
OH
CH
,CO
OH
CH
sCO
OH
3.6 X l
r3
4.1
X lO
A
2.0
X l
OA
6.
5 X
lO
-’ 1.
6X
lad
2.1
X l
o-’
(1.8
x
lr’)
- 32
28.5
29
.7
21.7
30
.4
- 24
.2
20.2
21
.9
7.9
12.9
26.4
8.
3 S
204
(2.7
X
1U
s)
21
-9
(1.0
x 10
-4)
19
-13
(3.7
x
10-S
) 22
-5
2.
8 X
lo5
18.2
-1
8.3
2.1
x 1o
-5
19.6
-1
4.2
1.2
x 1o
-5
24.0
+
0.6
6.0
X 1
0”
26.8
12
(7.5
) 9.
6 X
1O
-6
25.9
9.
9(5.
4)
1.2
X l
o-5
24.0
0.
6 1.
4X
1P
21.7
1.
3 1.
9X
1o-3
30
.0
29.5
2.
7 x l
o-*
10.1
-3
1.8
7.7
X l
o-4
17.9
-1
2.7
4.3
X 1
P 22
.1
0.2
2.5
X l
o-’
- -
8.5
X lo
-’
21.2
-1
5.2
1.6X
10
” 23
.5
- 6.
3
2.7
X lo
4 1.
1 X
104
1.
4X
l@
4.1
X lo
-5
8.0
X l
@
1.5
X 1
o-s
2.8
X lo
-
1.2
x lO
A
(84.
5 “)
4.
6 X
lo4
(8
4.5”
) 2.
3 X
lOA
(8
4.5”
) 2.
6 x
lO-’
(84.
5”)
26.3
23
.2
23.6
22
.3
21.5
13.4
1.
2 3.
0 -
3.8
- 0.
6
22.9
-
3.8
19.9
- _ - -
- 8.
0 S
167
-
S nmr
S L co
S 36
6 S
36
6 S
366
S 20
7 S
207
nmr
205
S 20
5 S
205
nmr
206
S; 1
6.6%
tra
m
prod
20
5 S;
16.
6%
tram
pr
od
205
S;K
;kfD
t 20
8 S;
K;k
tDf
208
S;K
;k?D
t 20
8 S;
K;k
tDt
208
S 20
7 S
167
S; 1
6.6%
tr
ans
prod
S nm
r S S;
pro
d.
is C
o(en
k (N
Oz)
NC
S+
S S S S S
202
203 68
68
71
71
205
205
205
209
209
167
364
364
364
364
74 J. 0. Edwards, F. Monacelli and G. Ortaggi
TABLE VI. Activation Parameters for Aquation of Isomeric Complexes of Type Co(en)zAX”+.a,b,e,d
cis tram
A X AH+ AS+ AH* AS* 6A H” 6AS+
Cl Cl 21.6 - 4.0 27.5 13.1 +5.9 +17.1 Br Cl 22.5 - 0.7 24.6 4.1 +2.1 + 4.8 OH Cl 22.5 7.9 25.6 14.6 +3.1 + 6.7 N3 Cl 21.1 - 4.3 23.1 2.2 +2.0 + 6.5 NCS Cl 20.2 -13.5 29.8 7.8 +9.6 +21.3 NOz Cl 21.8 - 3.4 20.9 -2.2 -0.9 + 1.2 NH3 Cl 24.9 - 4.3 23 -11 -1.9 - 6.7 Cl Br 23.3 4.8 26.0 10.6 -2.7 + 5.8 Br Br 23.2 5.6 25.5 9.4 +2.3 + 3.8 OH Br 22.7 12.1 24.4 14.1 +1.7 + 2.0 NCS Br 22.5 - 4.3 29.5 10 +7.0 +14.4 NH3 Br 22.5 - 9.6 24 -5.1 +1.5 + 4.5
a The reaction is Co(en),AZ”+ + H,O+ Co(en)ZAH,O”f’ + X-. ’ The quantity 6AH* is defined as A H* (tram) less AH* (cis); 6A S* is defined similarly. ’ Units of AH* arc kcal mol-‘, and of AS* are cal mol-’ deg-‘. d Data taken from Data Table References 52, 131, 136, 138, 139, 141, 87, 143, 109, 121, 128, 161 and 165.
sibility of a trans-effect in octahedral systems. In prac- tice, this is not easy. For example, in the isomeric sys- tems cis and tram Co(en)*AX”+ where A is a mono- dentate, non-leaving ligand and X- is the leaving group, one is not simply looking at the truns-effect of A. Rather, one is comparing the effect of A with that effect due to one end of an ethylenediamine ligand. Some data are given in Table VI. It is clear that the values of dS* for the tram complexes are generally more positive than those for cis complexes; a similar trend is seen in the values of AH*. The values of &l H’ decrease for ligand A in the order
NCS > CT > OH- > Br- 2 N3- > NOz- > NH3
and those for 6A S* in the order
NCS > Cl- > OH- 2 N3- > Br- > NOz- > NH3
Our knowledge of the trans-effect in octahedral systems is limited, and it seems possible that the magni- tude of the trans-effect will depend on the nature of the leaving group. Roughly, however, what we see in the above orders is that the values of the 6 are in opposite order to those of the trans-effect, at least for the unions. For the anions, Pal and Vuikzza report the order
Cl- = OH- < Br- < I-
and it has been suggested22b that I- ~1 NO*- for the trans-effect. Making the assumption that NH3 and one end of ethylenediamine have about the same trans-
effect, we may conclude that the trans-effect decreases the value of dH* (still considering anionic ligands) while lowering the value of dS* . This is explicable if
the trans-effect moves the mechanism toward a more associative nature; however, neither the assumption nor the conclusion can be considered definite, partic- ularly in view of the anomalous position of ammonia (which is a neutral ligand rather than anionic). Experi- ments relevant to these points would be welcomed.
It should be stressed here that, as suggested by PO& the observed kinetic trans-effect should be corrected for the thermodynamic trans-effect and this correction might change somewhat the sequence. Also the recent review of Byrd and Wilmarth23d makes a strong case for a D mechanism for octahedra having a strong truns-effect ligand.
The problem of the octahedral trans-effect is impor- tant, and we list here references bearing on this ques- tion that we have found during the course of our litera- ture survey.22*23
6. Solvolysis
Data on formation rates of solvo-complexes (other than aquo, of course) are given in Data Table II. One sees immediately that the amount of data in non- aqueous solvent systems is very much less than in water, and further that the variety of systems studied is such that generalization is almost impossible. The activation parameters cover a wide range, and the values of AS* are seen to be both positive and nega- tive. Whether this is due to experimental uncertainties or to variable nature of the complex-solvent interaction is not known.
Ligand Replacements in Octahedral Complexes 15
7. Acid-catalyzed Aquation
The cleavage of a metal-ligand bond can be facilit- ated by protonation of the leaving group. Using Co (en kb+ as the substrate example, the postulated mechanism is
Co(en)2Fz+ + H+ e Co(en)zF(FH)Z+ (fast)
Co(en)zF(FH)Z+ + HzO-+ Co(en)2F(H20)2+ + HF (rate)
with the rate-determining step involving the cleavage of the CO-FH bond. The rate has been found to be faster in DzO than in H,O. Since D30+ in DzO is a stronger acid than H30+ in HzO, the isotope experi- ment indicates that proton transfer occurs in a rapid equilibrium prior to the rate step. Acid catalysis is observed when the leaving ligand is basic towards protons; some such ligands are N3-, CN-, F, NOz-, SOd2-, HP0d2-, SO3’-, ox’-, mal’-, COJ2- and various acetates. This much seems certain, but the extent of participation by water in this step is not known.
which ranges from 3.1 X lo-’ to 1.3 X lo3 shows a distinct trend. Since &lG’ varies by seven kcal mar’, we should see some changes in the enthalpy and en- tropy of activation terms. However no clear trend is observed, and any trend must be covered by other factors. It is, therefore, interesting to see the ubiqui- tous d H’ /A S” compensation effect showing up in the values. A plot of 6AH* values against dAS* values forms a rough straight line with slope of 340” K which is uncomfortably close to the 25” C (298°K) of the data.
8. Base Hydrolysis
The dispute over the mechanism for the rapid base hydrolysis such as for example
Co(en)2Clz+ + OH--, Co(en)2Cl(OH)’ + CT
Comparison of the activation parameters in Data Table III with those for the analogous complexes in Data Table I (aquation reactions) shows no consistent difference. We expected that the acid-catalyzed path would be related to the aquation path in some non- complicated way. For instance, were the mechanism essentially dissociative in both cases, the &lS* values would be expected to be near the difference between the protonated ligand and the ligand itself in water solution. Unfortunately although in some instances this situation seems to occur, the lack of entrdpy data for many leaving groups prevents a complete analysis.
centered about the mode of action for hydroxide ion. The rate law is first-order in base. A direct displace- ment such as obtains for base hydrolysis in many organic compounds was favored by some research groups. The alternative mechanism invoked the uni- molecular heterolytic scission of the conjugate base of the complex. Now, there is quite general agreement that this conjugate base mechanism is the preferred one.
Some data which compare rates and activation parameters for acid-catalyzed and normal aquations are present in Table VII. Not even the ratio k,,/k,
We believe, however, that this is a particularly clear example of a reaction whose progress exhibited activa- tion parameters giving a definitive clue as to the actual mechanism, and for the purpose of demonstrating the importance of these parameters, we shall discuss some of the arguments here. Some recent reviews concern- ing this mechanism are available;‘~3’4~‘0”4~24 details of
TABLE VII. Comparison of Activation Parameters for Acid-Catalyzed and Normal Aquationsa
Complex kh k, Wk, AH*,, AH’, 6AH’ AS*,, AS*, 6A.P
Fe(HzO)sN32+ 5.1 20. 0.26 19.6 14.7 4.9 10.5 - 3.2 13.7 Cr(H20)5FZ+ 1.4 x lo4 6.2 x lo-“’ 23 24.5 28.7 - 4.2 -12.4 - 4.4 - 8.0 Cr(H20)5CNZ+ 5.2 x lOA 1.2 x 10-S 43 17.0 27.9 -10.9 -16.4 +12.7 -29.1 Cr(H20)5N32+ 2.3 x lo-’ 4.1 x lo+ 21 23.2 32.4 - 9.2 - 8.3 +16.4 -24.7 Cr(H20)&04* 2.3 x lp 7.5 x lo-’ 0.031 26.5 21.9 + 4.6 - 1.3 - 1.3 +11.7 Co(NH&F’+ 1.1 x lOA 8.7 x lp 1.3 x lo3 29.6 20.7 8.9 22.6 -21.4 44.0 Co(NH&N02’+ 2.6 x lOA 8.2 x lO-” 32 18.4 23.9 - 5.5 -22.7 -11.1 -11.6 CO(NH~)~OCOCH~‘+ 3.2 x lOA 2.7 x lp 1.2 x 10’ 25 25 0 2 -8 +10 Co(NHs)50xHZ+ 2.0 x lo-7 2.2 x loa 9.1 22.7 28.4 - 5.7 -14 + 1 -15 Co(NH&04+ 9.5 x 10-7 8.9 x 1O-7 1.1 28.4 22.7 5.7 9.2 -10 +19.2 Rh(NH&Od+ 1.1 x lOA 1.6 x lOA 0.69 28.5 21.4 7.1 9.9 -13.3 +23.2
a The following are the definitions for symbols in the table: kh = rate for acid-catalyzed aquation; k, = rate for normal aquation; A H* h = enthalpy of activation for acid-catalyzed aquation; AH* a = enthalpy of activation for normal aquation; 6AH” = difference in activation enthalpies (AH* ,-AH* .); AS* - h - entropy of activation for acid- catalyzed aquati0n;A.S’. = entropy of activation for normal aquation; and 6AS * = difference in activation entropies (A S* ,,-A S* .).
DA
TA
T
AB
LE
II
I. A
cid-
Cat
alyz
ed
Aqu
atio
n.
Com
plex
W
f)
PH
M
ediu
m
k A
H”
AS*
Fe(
HZ
O)S
N32
+
Fe(
H20
)sS
Os+
C
r(H
zO)s
F*+
C
r(H
20)&
NZ
+
Cr(
Hz0
)sN
3*+
C
r(H
20)5
0NO
Z’
Cr(
Hz0
)50P
OzH
gZ+
C
r(H
ZO
)sO
S03
+
cis-
Cr(
H,0
)d(C
N)2
+
Cr(
NH
3)5F
Z+
C
r(N
H&
(ON
O)‘+
C
r(N
H3)
5(0C
OC
Cl~
)2+
~
is-C
r(en
)~F
~’
cis
-Cr(
en)2
F(O
NO
)+
~is
Cr(
en)~
(H~
O)(
ON
0)~
+
cis
-Cr(
en)z
(O
NO
X+
tr
un
s-C
r(en
),C
l(O
NO
)+
tran
s-C
r(en
~B
r(O
NO
)+
rran
~-C
r(en
)~(~
,0)(
0~0)
~+
tr
ans-
Cr(
en)Z
(ON
O)z
t tr
ans-
Cr(
en)z
(DM
SO
)(O
NO
)Z+
tr
ans-
Cr(
en)2
(DM
F)(
ON
O)Z
+
Cr(
mal
)a3-
C
r(M
e-m
al),
3-
cis
-Cr(
HZ
O)z
(ox)
z-
cis
-Cr(
HzO
)z(m
alh
- ci
s -C
r(H
zO)Z
(mal
)z-
tran
s-C
r(H
zO)~
(mal
&-
Co(
NH
,),F
’+
Co(
NH
j)5(
NO
z)‘+
C
o(N
Hs)
5(N
O#+
Co(
NH
&(o
xH)‘+
Co(
NH
a)s(
OS
Oa)
+
cis-
Co(
en)Z
(NO
zh+
ci
s-C
o(en
)2(N
3)2+
1.0
co.3
(L
i,H
)C10
4 1.
0 0.
3-1.
7 (N
a,H
)C10
4 1.
0 o-
1.15
(L
i,H
)C10
4 1.
0 o-
3.1
(Li,
H)C
104
1.0
0.6-
3.15
(N
a.H
)ClO
., 1.
0 o-
2 1.
0 O
-l.1
1
.o
o-1.
3
2.0
_
1.0
0 1.
0 -
0.13
l-
2 0.
01-0
.15
0.8-
2 0.
15
0.15
0.
15
0.15
0.
15
0.15
0.
15
0.15
0.
15
1.0
1.0
2.0
2.0
_ 1.0
0.11
2 -+
O
1.0
0.1
0.1
0.1
1.0
1.0
3.5
-
20.8
2 20
.82
20.8
2 20
.82
20.8
2 20
.82
20.8
2 20
.82
20.8
2 o-
1 o-
1
2-3
0.3-
l - 0 l-
l.7
_ _ l-2
l-2
0.3-
2
7.0
O-2
.3
<o
_
(Na,
H)C
104
(Li,
H)C
lOd
(Li,
H)C
104
(Na,
H)C
104
HC
lOz,
K
N03
(N
a,H
)C10
4 H
C10
4 (N
a,H
)C10
4 (N
a,H
)C10
4 (N
a,H
)C10
4 (N
a,H
)C10
4 (N
a,H
)C10
4 (N
a,H
)CIO
., (N
a,H
)C10
4 (N
a,H
)C10
4 (N
a,H
)C10
4 (N
a,H
)C10
4 (N
a,H
)ClO
,,
(Na,
H)C
104
(Na,
H)C
104
_ HC
IO.,
(K,H
)NO
z,
HC
lO.,
(K,H
)NO
a an
d u
rea
(Na,
H)C
104
(Na,
H)C
104
(Na,
H)C
104
(Na,
H)C
104
(Na,
H)C
104
_
5.1
3.7
1.4x
lo
4 5.
2 x
lo-4
2.
3 x
lo-’
3.2
X 1
0-l
1.7
x 10
” 2.
3 x
lo+
8.
3 x
lOA
1.
5 x
lo-’
5.1
x l@
2x
1o-3
5.
3 x
10-s
1.
6X
lo-2
1.
3 x
10-l
5.
0 x
10-l
2.
8 x
lo-’
3.6
x lo
-’ 9.
6 X
lo-
’ 6.
5 x
lo-’
8.0
x IO
-’ 7.
6 x
lo-’
3.6
x lo
4 5.
9 x
lOA
19.6
10
.5
10.4
_2
1 24
.5
- 12
.4
17.0
-1
6.4
23.2
-
8.3
19.8
9(
5.6)
18
.1
-24.
2 26
.5
- 1.
3 19
.9
- 5.
9 28
4
11.9
-2
4.8
21.6
1.
6 23
-
0.9
20.9
3.
4 20
.1
+
4.9
22
I8
21.0
4.
9 20
.3
3.0
19.8
3.
2 24
.3
17.6
-
_
20.1
3.
8 23
.4
4.2
_ -
2.3
X 1
0”
2.3
x 10
” 6.
5 x
lo-’
1.1
x 10
” 1.
1 x
lo4
4.0
x lo
+
2.6
x lo
-6
23.9
_ 21
.8
24.3
29
.6
38.2
18
.4
- 4.
5 _ -
4.7
0.4
22.6
31
.2
-22.
7
3.2
x IO
4 25
6.
2 x
lo-’
26
5.9
x lo
-+
29
Z(3
) 1
2.0
x lo
-’ 22
.7
-14
9.5
x lo
-’ 28
.4
9.2
1.4x
1o
-5
25.0
3.
1 2.
4 x
lo4
26.1
12
.5
_
Com
men
ts
Tab
le
Ref
. N
o.
SS
F
SS
F ; p
roba
bly
S-b
onde
d S
S
s SW
S
S
S
S S
S
T
S;
lOO
%ci
s pr
odu
ct
S;
100%
ci
s pr
odu
ct
S;
100%
ci
s pr
odu
ct
S; 1
00%
tr
am
prod
uct
S
; 10
0%
fran
s pr
odu
ct
S;
100%
tr
ans
prod
uct
S
; 10
0%
trar
rs p
rodu
ct
S ;
100
% t
ram
pr
odu
ct
S ;
100
% t
rans
pro
duct
S
; on
e m
al*-
is
lost
S
; th
e pr
odu
ct
is tr
ans
- C
r(m
e-m
al)z
(OH
z)z-
S
; on
e ox
*- i
s lo
st
S;
one
mal
’- is
los
t S
S
T
S S
S
S S;
wh
enp
=
1.
0,
AH
* =
22
,AS”
=
-20
S S S S
75
280 9 14
15
21
0 21
1 24
212 37
21
3 32
0 21
4 27
8 27
8 27
8 27
8 q
278
278
278
278
278
217
305
215
216
157
157 83
92
93
97
97
82
96
102
218
218
L&and Replacements in Octahedral Complexes 77
the experimental results plus other references are sum- marized in these articles.
Let us first consider the direct displacement me- chanism. The mechanism requires both particles in the transition state with a fair degree of reagent orientation. It is expected from known entropies of activation for associative processes that a value of about -15 cal rnor’ deg-’ for AS* would be found.*’
The alternative mechanism, designated SNICB (for substitution, nucleophilic, unimolecular, conjugate base), is postulated to be made up of three steps. With Co(NH3)5Br2+ as substrate, the steps are as follows:
Co(NH3)5Br2+ + OH- # Co(NH3k(NH2)Br+ + Hz0 (fast)
Co(NH3)4(NH2)Br++ Co(NH3),(NH2)‘+ + Bi (rate)
Co(NH3&(NH2)‘+ + H20+Co(NH3)s0H2+ (fast) The first step is a rapid equilibrium (somewhat akin to neutralization of a weak acid). The second step is rate-determining, and it is the unimolecular scission of the intermediate formed in the first step.
A positive AS* value is predicted for the SNICB mechanism. The first step
NH-M-X”+ + OH- P H,O + N-M-X@-*)+
is closely similar to known “neutralization” reac tions in the literature; some of these are given in Table VIII along with the estimated values of AS”,,,. These are positive and large because of the consider- able charge neutralization. The second step, which involves some charge separation concurrent with formation of two particles from one, is expected to have a AS” 2 near to zero as is the case for aquation of Co(NH&X*+ where X- is a large leaving group. Using the two values AS”,,, = 34 (average value from Table VIII) and AS* z = 0, we obtain for AS* an estimated value of +34 cal mar’ deg-‘.
The bulk of the experimental values for AS* in Data Table IV lie between +20 and +40, and there is
TABLE VIII. Some Entropies of Neutralization of Aquo- complexes.a’b~c
Complex K, AH’ion AS’io,, AS”,,
V(Hz0)e3+ 2 x 1c3 10 20 39 Cr(HZ0)63+ 2x10-4 9.4 14 33 Mn(H20),,3’ 9 x 10-l 4.8 15.7 35 Fe(H20)b3+ 6x l@ 12.3 31 50 C0(Hz0)6~+ 2 x 1o-z 10 25 44 Rh(H20)b3+ 4 x lOA 4.3 -1 18 Rh(NH&0Hz3+ 4 X lo-’ 6 -9 10
a K., AHoion, and ASoion are for the process HzO-M-X5”+ P HO-M-X5”-1 + H+
b AS”,, is for the process H20-M-X5” + OH- # HO-M-X5”-’ + HzO.
’ Data from text ref. 25.
DA
TA
TAB
LE
IV.
Bas
e H
ydro
lysis
.
Com
plex
P
(M)
PH
Med
ium
k
AH
* A
S*
Com
men
ts
Cr(
H*0
)5py
3+
1.0
O-3
C
r(H
*O)&
l*+
1.0
o-1.
7 C
r(H
*O)s
B?+
1.
0 o-
1.3
Cr(
H*O
),Bf+
2.
0 -
(Na,
H)C
104
(Li,H
)C10
4 (L
i,H)C
104
_
Cr(
H*O
)sI*
+ 1.
0 04
.7
(Li,H
)C10
4 C
r(H
*O)s
IZf
1.07
O
-O.6
(N
a,H
)ClO
.,
Cr(
H*0
)512
+ 1.
0 o-
1.7
Cr(
H*O
)sSC
N*+
1.
0 2
Cr(
H*0
)5N
**+
1.0
0.4-
2.15
C
r(H
*0)5
0NO
**+
1.0
O-l.
1 C
r(H
*0)5
0N0*
2+
1.0
O-l.
1 C
r(H
*0)5
0S03
+ 1.
0 o-
1.3
cis
+~~~
wC
~(H
*O)~
(NC
S)SC
N+
1.0
o-1
trans
(?)-
Cr(
H*O
).,C
l*+
0.5
10-3
.7
Cr(
NH
*)sF
*’
0.1
- C
r(N
H,),
F*+
0.1
13
Cr(
NH
,)sF*
’ 0.
11
_
(Li,H
)C10
4 (N
a,H
)C10
4 (L
i,H)C
104
(Li,H
)Cl0
4 (L
i,H)C
104
LiC
lO,
(Na,
H)C
104
(Na,
H)C
I N
a(N
O,,O
H)
NaO
H
EtO
H-H
*O
114.
5 N
a(C
lO.+
,OH
) M
eOH
-H*O
1:
4.5
EtO
H-H
*O
114.
5 N
a(C
104,
0H)
Na(
C10
4,0H
) N
a(C
104,
0H)
9.9
x lo
3 2.
8 x
lo6
9.2
x lo
7 1.
1 x
10”
(30°
C)
(4.0
x
109)
8.
2 x
lo9
(30°
C)
3.4x
lo
9 2.
7 x
10”
2.1
x lo
3 1.
0x
ld
1.4x
10
’ 3.
2 x
lo5
7.3
x 10
” 2.
6 x
10’
2.7
X l
o-+’
3.
2 x
lo-’
6.
3 x
lOA
22.3
34
.5
S 16
.1
25.0
S
; see
bel
ow*
13.8
24
.0
T; s
ee b
elow
* -
- S;
see
bel
ow*
7.3
9.9
ST;
see
belo
w*
- -
S; s
ee b
elow
*
15.6
37
.2
S; s
ee b
elow
* 14
.5
31.0
(28.
7)
S; s
ee b
elow
* 23
.9
36.6
S;
see
bel
ow*
11.6
17
.1
S; s
ee b
elow
* -
_ S;
see
bel
ow*
14.4
14
.9
S; s
ee b
elow
* 11
.6
21.9
S
_ _
S 23
.2
-6.2
T
32.4
20
.6
P 25
.5
3.2
T
Cr(
NH
a)sC
l*+
Cr(
NH
*)5C
I*C
0.
1 0.
11
11.5
-13
_ 1.
8 x
1O-3
2.
5 x
1O-3
5.2
x lo
-’
7.2
x lC
r*
3.7
1.8
x 10
-s
8.1
x 10
” 2.
3 x
10”
210(
40.5
”C)
26.1
16
.5
P 41
27
.7
22.5
T
45
Cr(
NH
*)&
l*+
0.11
-
27.6
23
.6
7 45
Cr(
NH
*)5B
?+
Cr(
NH
*)sI
*+
Cr(
NH
*)sN
**’
Cr(
NH
3)sN
CS*
+ C
r(N
H*)
sNC
S*+
cis-
Cr(
en)*
F*’
0.1
0.1
0.2
0 o-o.
5 0.
010
11.5
-13
211.
5 0.
7-1.
3 _ 7-
13.7
7.
9
_
25.7
22
.5
P 26
.2
26.8
P
24.9
2.
9 S,
(10
” ra
nge)
35
.0
35.6
ST
31
.4
21
S -
- T
cis-
Cr(
en)*
Cl*
+ 0.
10
11.3
-14
cis-
Cr(
en)*
OH
Cl+
0.
10
10.1
-10.
7 tru
ns-C
r(en
hCl*
+ 0.
10
11.3
-14
trans
-Cr(
en)*
OH
Cl+
0.
10
9.8-
10.8
Fe
(OH
*)sC
12+
3.0
CO
.6
Co(
NH
3)sF
*+
O(e
xt)
-
NaO
H
Buf
fer
B(O
H)-
JH*B
O*
Na(
N03
,0H
) N
a(C
104,
0H)
Na(
N03
,0H
) N
a(C
104,
0H)
(Na,
H)C
104
2.7
x lo
-*
-
2.2
-
3.7
x lo
-*
-
<3x
lo-*
-
3.4
x 1o
14
-
1.3
x lo
-2
26.1
T
- S;
96
% c
is
prod
T
- _ 20
.4
S; 8
7 %
tra
m
prod
uct
S; n
ote
unus
ual
k T
Tabl
e R
ef.
No.
325 9 10
11
12
13 9 18
15
20
19
24
331 28
38
33
8 45
41
41
326 46
21
3 21
4 55
57
55
57
73
222
* O
rigin
al
resu
lts
give
n by
rat
e la
w
k =
kr[H
+]-‘.
A
ctiv
atio
n pa
ram
eter
s an
d ra
te
cons
tant
s ar
e co
rrec
ted
for
the
k,,A
H”
and
AS
" of
the
pr
oces
s H
*O
P H
+ +
OK
, k,
=
1.0x
lC
?,A
HO
=
13.3
,A.S
” =
-19.
3.
Co(
NH
,),F
’+
0.11
Co(
NH
s)sF
*+
0.11
Co(
NH
3)5C
l*+
O
(ext
) C
o(M
H&
Cl’+
0.
1 C
o(N
H3)
sClZ
+
0.05
-0.0
05
Co(
NH
~)&
I’+
O
(ext
) C
o(N
H&
B?+
O
(ext
) C
o(N
Hg)
sB?+
1.
0 C
o(N
H3)
gB?+
0.
05~
.005
C
o(N
H&
B?+
O
(ext
) C
o(N
H,)
,B?+
va
riab
le
Co(
NH
&B
r’+
C
o(N
H&
I’+
C
o(N
H3)
$+
Co(
NH
&I’
+
Co(
NH
3)s1
2+
Co(
NH
&N
Oz’
+
Co(
NH
&N
3’+
C
o(N
H&
NC
S’+
C
o(N
H&
NC
S’+
C
o(N
H&
ON
O’+
C
o(N
H&
ON
O*+
C
o(N
H&
NH
$O#+
C
o(N
H&
(NH
S03
)+
CO
(NH
&O
CO
CH
Clz
*+
Co(
NH
&O
CO
CC
ls*+
C
o(N
H3)
s0C
OC
F3*
+
CO
(NH
~)~
OC
OC
F~
*+
Co(
NH
&O
CO
,+
Co(
NH
3 )5
(ox)
+
Co(
NH
&(m
al)
+
Co(
NH
3)s(
fum
arat
e)+
C
o(N
H3)
sOS
03+
C
o(N
H&
OS
zOz+
C
o(N
H&
OS
zOz+
C
o(N
H&
OP
03
Co(
en)3
3+
cis-
Co(
en),
NH
3N02
’+
cis-
Co(
en)z
NH
3NC
SZ
*
cis-
Co(
en)z
NH
3C12
’
cis-
Co(
en)z
(NH
zOH
)C12
+
ci~
-Co(
en)~
(NH
~0H
)Br*
’ ci
s-C
o(en
)z(N
HzM
e)C
lz+
ci
s -C
o(en
)Z(N
H2M
e)C
12+
O(e
xt)
0.1
O(e
xt)
1.0
O(e
xt)
O(e
xt)
O(e
xt)
O(e
xt)
0.00
7 0.
1 0.
12
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
O(e
xt)
1.0
>O
.l
0.03
3-0.
1
0.03
3Al.
l
0.10
0.1
0.1
0.10
0.
10
- 12-1
4 11
.7-1
2.7
- 12.0
-13.
4 11
.7-1
2.7
t,P
,itia
l)
13.5
-14.
0 13
.0-1
3.1
12.8
-13.
5
_ 12.3
-14.
0 13
.0-1
4.0
13.6
-14.
0 13
.6-1
4.0
13.3
-12.
7 12
.6-1
3.3
11-1
2.6
>13
12
.5-1
3.0
12.5
-13.
0
9.2-
9.8
11.5
-12
11.5
-12
11.5
-12
9.2-
10.0
MeO
H-H
Z0
114.
5 E
tOk
H20
11
4.5
Na(
C10
4,O
H)
NaO
H
NaO
H
Na(
ClO
.,,O
H)
NaO
H
NaO
H
NaO
H
NaO
H
Na(
ClO
+O
H)
N&
Clo
d,
NH
, - _ N
aOH
N
aC10
4 L
iC10
4,N
aOH
N
aClO
,, N
a(C
lO.,,
OH
) N
a(C
l,O
H)
Na(
Cl,
OH
) N
a(C
l,O
H)
Na(
CI,
OH
) N
a(N
03,0
H)
Na(
Cl,
OH
) N
a(C
I,O
H)
Na(
Cl,
OH
) N
a(C
lO,,,
OH
) N
aOH
,N&
N03
_ N
a(C
104,
0H)
NaO
H
NaO
H
NaO
H
KC
1
NaC
104
NaC
lO,,
NaC
104
KC
1
1.0
x 10
-z
26.4
2.1
x lo
-2
26.5
1.5
27.6
0.
61
-
0.81
28
.7
1.6
26.6
6.
2 27
.6
1.4
-
6.0
23.5
8.
9 27
.0
5.2
(30°
C)
- 10
-
6.3
27.2
17
.4
27.2
3.
70
21
23
28.3
4.
2 x
1OA
37
.4
3.0x
lo
-4
32.6
5.
0 x
lv4
34.0
1.
4 x
1o-3
21
.6
15
28.1
12
28
.8
1.0x
10
2 32
2.
5 x
lO-’
41.2
5.
8 x
1O-3
28
.9
2.2
x lo
-*
23.3
2.
1 x
10-Z
22
.7
1.6
x lo
-*
27
3.3
x lo
4 30
.0
2.5
x l@
31
.7
2.8
x lO
-’ 28
.0
8.0
x lo
-’ 28
.5
4.9
x lc
rZ
26.3
6x
lo
-5
27.6
1.
1 x
l@
30.4
5.
0 x
lo-’
36.8
(1
.1 X
10-
9)
38.6
5.
1 x
1Crs
33
.3
2.9
x l(
r3
30.6
8.1
-
7.0
23.4
48
23
.7
7.3
23.4
13
-
20.9
T
22.7
T
30.7
(34.
8)
- 37
31.6
37
.7
_ 23
36.4
- - 36
.4
38.4
19
(14.
5)
42.6
42
.4
34.7
40
.4
1.9
41.0
43
58
46
28
.8
12.5
10
24
18
32
.2
14.4
18
.3
24.0
14
.4
25.7
36
.0
30
33.5
32.5
- 23
.8
28.7
23
.9
-
T
SW
S
S
; (1
3.4”
ra
nge
) T
SF
S
S
S
S pH s
tat
S S
T S,T
S
,T
S,T
K
pH
sta
t S
S
S
S
S
S - co
o S
S
S
S
S
T
- R
S
T
S;
90%
ci
s pr
od.
T ;
100
% c
is p
rod.
T
T
T
T;
100%
ci
s pr
od.
45
Ir
o;j’
222
G s
223
R
85
3
224
2 i: 22
2 s.
223 85
B
225
E
“a
226
a
227
5
228
h 6
229
6 90
22
2 23
0 91
46
231
228 94
99
99
98
98
23
2 23
3 23
4 23
5 23
5 23
5 99
103
337 95
22
1 23
6 23
7
238
111
111
111
238
;1
DA
TA
T
AB
LE
IV
. (C
ont.
) g
Com
plex
p(
M)
PH
M
ediu
m
k dH
* dS
* C
omm
ents
T
able
R
ef.
No.
cis-
Co(
en)*
(NH
*Me)
B?’
0.
1 ci
s-C
o(en
)*(N
H*E
t)C
l*+
0.
1 ci
s-C
o(en
)*(N
H*E
t)C
l*+
0.
1
cis-
Co(
enX
(NH
*Et)
CI*
+
cis-
Co(
en)*
(NH
*Et)
Br*
’ ci
s-C
o(en
)*(N
H*-
n-P
r)C
l*+
ci
s-C
o(en
)*(N
H*-
n-P
r)C
I*+
ci
s-C
o(en
)*(N
H*-
n-P
r)B
?+
cis-
Co(
en)*
(NH
*-i-
Pr)
Cl*
+
cis-
Co(
en)*
(NH
*-i-
Pr)
Cl*
+
cis-
Co(
en)*
(NH
*-i-
Pr)
B?+
ci
s-C
o(en
)*(N
H*-
n-B
u)C
l*’
cis-
Co(
en)*
(NH
*-n
-Bu
)Cl*
’ ci
s-C
o(en
)*(N
H*-
All
yl)C
l*+
ci
s-C
o(en
)*(N
H*-
All
yl)B
? ci
s-C
o(en
)*(N
H*C
H*C
H*O
H)C
l*’
cis-
Co(
en)*
(NH
*(C
H*)
~C
H*O
H)C
l*+
ci
s-C
o(en
)*(N
H*(
CH
*)4C
H*O
H)C
l*f
cis-
Co(
en)*
(NH
*(C
H*)
5CH
*0H
)ClZ
+
cis-
Co(
en)*
(NH
*-P
rop-
2-yn
yl)C
l*+
ci
s-C
o(en
)*(N
H*-
Pro
p-2-
ynyl
)Bf+
ci
s-C
o(en
)*(N
H*(
CH
*)sC
OO
Me)
C12
+
cis-
Co(
en)*
(NH
*(C
H*)
sCO
O-)
C1*
+
cis-
Co(
enX
pyC
l*+
ci
s -C
o(en
)* @
-pi
c)C
l*+
ci
s-C
o(en
)*(y
-pic
)Cl*
+
cis-
Co(
en)*
@-C
H30
-py)
Cl*
+
cis-
Co(
en)*
Cl*
+
cis-
Co(
en)*
ClB
r+
cis-
Co(
en)*
BrC
l+
cis-
Co(
en)*
(OH
)F+
ci
s -C
o(en
)* (
OH
)Cl+
ci
s-C
o(en
)*(O
H)B
r+
cis-
Co(
en)*
(OH
)(N
O:)
+
cis-
Co(
en)*
(OH
)(N
O*)
+
cis-
Co(
en)*
(OH
)N3+
ci
s-C
o(en
)*(O
H)(
NC
S)+
ci
s-C
o(en
)*(O
H)(
NC
S)+
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.5
0.1
0.1
0.1
_ _ 0.1
0.1
0.1
0.1
- - 0.00
1-0.
01
0.00
1~.0
1 0.
001-
0.01
0.
10
0.00
1-0.
01
0.00
1-0.
01
0.10
0.
050-
0.10
0.
05
- 0.05
0~.1
11.5
-12
NaC
104
50
11.5
-12
NaC
104
6.5
4.65
-5.6
5 B
uff
er
12
(Na.
H)O
CO
CH
3
9.2-
10.2
11
.5-1
2 11
.5-1
2 9.
2-10
.0
11.5
-12
11.5
-12
8.8-
9.6
11.5
-12
9.2-
10.0
12
.4-1
3.7
11.5
-12
11.5
-12
9.0-
9.6
1 (N
a,H
jOC
OH
K
C1
NaC
104
NaC
104
K(C
l,N
O*)
N
aC10
4 N
aC10
4 K
C1
NaC
104
KC
1 K
CI-
NaO
H
NaC
104
NaC
104
KC
1
13
47
11
13
2.7
x l
o*
17
52
4.2
x lo
* 13
6.
5 6.
4 1.
2 x
lo*
20
2.7
X 1
0-l
2.7
x 10
-l
2.5
x 10
-l
3.3
57
14
1.5
x lo
-’ 1.
6 x
1O
-3
1.3
x 1o
-3
1.3
x 1o
-3
1.2
x 10
” 7.
1 x
lo*
2.6
x l
o3
8.4
x l
o*
1.2
x lo
-’ 12
86
- 11.5
-12
11.5
-12
12.4
-13
11-1
1.5
- - - 11.0
-12.
0 11
.0-1
2.0
11.0
-12.
0 11
.5-1
2.0
11.0
-12.
0 11
.0-1
2.0
13.0
12
.7-1
3.0
12.7
12-1
2.3
NaC
lO.,
NaC
104
bora
x bu
ffer
s bo
rax
buff
ers
- NaO
H
NaO
H
NaO
H
Na(
N03
,0H
) N
aOH
N
aOH
N
aOH
N
aOH
N
aOH
- N
aOH
- 2.5
x l
@
2.8
x 1O
-3
2.3
x 1
O-3
1.
6 x
lo-
* (3
5°C
)
23.7
28
.8
23.5
24
.0
25.4
32
- 23.7
23
.4
- 23.7
23
.4
_ 23.7
- - 23
.4
23.8
_ _ _ - 23
.4
23.7
_ - _ _ _ _ 24
.0
22.5
22
.1
22.7
21
.8
21.9
30
.3
- - - -
- 28.6
24
.8
- 32.1
25
.6
_ 33
- _ 23.7
30
.8
_ _ - - 22.3
29
.0
- - - - - - 35.0
32
.6
29.0
13
.4
19.5
23
.8
_ _ - _ _
T
T
T
T;
100%
ci
s pr
od.
T
T
T;
100%
ci
s pr
od.
T
T
T;
100%
ci
s pr
od.
T
T;
100%
ci
s pr
od.
SS
F
T
T
T;
100%
ci
s pr
od.
S,T
S
,T
S,T
T
T
S
SF
, pH
sta
t S
sF, p
H s
tat
T
T
T
T
T;
37%
ci
s pr
od.
T;
30%
ci
s pr
od.
T;
40%
ci
s pr
od.
T
T;
97 %
cis
pr
od.
T;
96%
ci
s pr
od.
S
T S,T
T
T
111
111
112
238
111
111
238
111
111
238
111
238
239
111
111
238
347
347
347
111
111
361
361
159
4
159
P
159
!z
159
g 24
0 &
24
0 “J
24
0 3
129
240
f
240
f:
236
$
241
9
138
:
242
b 24
1 2 8.
cis
-Co(
en)Z
(OH
)(O
CO
CH
3)+
cis-
Co(
en),(
OH
)mal
ci
s-C
o(en
)z(N
3)N
3+
cis
-Co(
en)z
(N3)
NC
Sf
cis
-Co(
en)z
(NO
z)C
1+
cis-
Co(
en),(
N02
)N02
+ ci
s-C
o(en
),(N
Oz)
NC
S+
cis-
Co(
enX
(NC
S)N
s’
~i.s
-Co(
en)~
(NC
S)N
0~+
cis-
Co(
en)z
(NC
S)N
CS+
ci
s-C
o(en
)z(O
CO
CH
3)2C
C
o(en
),OA
ZO+
Co(
en)z
ox+
Co(
en)z
ox+
Co(
en)2
mal
+ tra
ns-C
o(N
H&
(NO
z)C
l+
trans
-Co(
NH
3)4(
N02
)BrC
truns
-C
o(N
H3)
4(N
CS)
Clf
trans
-Co(
en)z
(NH
3)N
022+
tra
ns-C
o(en
X(N
H3)
NC
SZ+
tram
-Co(
enX
FZf
trans
-Co(
en)z
Clz
+ tra
ns-C
o(en
)2C
lBr+
tra
ns-C
o(en
)zB
r2+
trans
-Co(
en),B
rCl+
tra
ns-C
o(en
),(O
H)F
+ tra
ns-C
o(en
)2(0
H)C
l+
trans
-Co(
en)z
(OH
)Br+
tru
ns-C
o(en
)Z(N
HB
)NC
S2+
trans
-Co(
en)Z
Fz+
trans
-C
o(en
XC
L+
trans
-C
o(en
ji
(&H
)N02
+ tra
ns-C
o(en
k(O
H)N
OZ+
tra
ns-C
o(en
)2(0
H)N
g+
trans
-Co(
en)z
(OH
)Ng+
tru
ns-C
o(en
)z(O
H)N
CS+
tra
ns-C
o(en
)z(O
H)N
CS’
tra
ns-C
o(en
)z(O
H)O
CO
CH
a+
tran
s -C
o(en
)z(C
N)C
1+
trans
-Co(
en)z
(CN
)Br’
tr
am-C
o(en
)z(N
02)C
l+
tran
s-C
o(en
)2(N
02)Z
f tra
ns-C
o(en
),(N
Oz)
NC
S+
0.01
4 - 0.
05
- 0.00
1-0.
01
0.03
3-0.
10
0.05
0-0.
10
- 0.05
-0.1
0 0.
01-0
.05
0.01
4 1.
0 0.
01-0
.03
3.4
- 0.3
0.3
0.21
0.03
3-0.
10
0.05
0-0.
10
- 0.00
10-0
.010
0.
0010
-0.0
10
- 0.00
10~.
010
0.10
0.
0010
-0.0
10
0.00
10-0
.010
0.
050-
0.10
- 0.
001-
0.01
0.
033-
0.10
0.
05-0
.10
0.05
_ 0.
05-0
.10
- 0.01
4 0.
010
0.00
5 0.
0010
-0.0
10
0.03
3-0.
10
12.0
N
aOH
12
-14
NaO
H
12.7
N
a0I-
i -
-
11.0
-12.
0 N
aOH
12
.5-1
3.0
NaO
H
12.7
-13.
0 N
aOH
_ 12
.7-1
3.0
12.0
-12.
7 12
.0
11.1
-14
12.0
-12.
5 14
- NaO
H
NaO
H
NaO
H
Na(
C10
4,0H
) N
aOH
N
aOH
12-1
4 13
.0-1
3.5
13.0
-13s
12.5
-13.
0 12
.7-1
3.0
- 11.0
-12.
0 11
.0-1
2.0
11.0
-12.
0 N
aOH
13
N
a(N
03,0
H)
11.0
-12.
0 N
aOH
11
.0-1
2.0
NaO
H
12.7
-13.
0 N
aOH
_ 11
-12
12.5
-13.
0 12
.7-1
3.0
12.7
NaO
H
NaO
H
NaO
H
NaO
H
- 12.7
-13.
0 N
aOH
-
-
12.0
N
aOH
12
.0
NaO
H
11.7
N
aOH
11
.0-1
2.0
NaO
H
12.5
-13.
0 N
aOH
NaO
H
Na(
N03
,0H
) N
a(N
03,0
H)
1
Pipe
ridin
e,2,
6-
dim
ethy
lpyr
idin
e-
HN
Os
buff
ers
NaO
H
NaO
H
NaO
H
NaO
H
8.2 x 1
O-3
25
.8
4.3
x lo
4 26
.5
6.6
x 1o
-3
-
2.7
x 1C
r3
-
1.2
22.5
3.
7 x
1o-5
31
.9
4.3
x 10
-4
29.6
6.
0 x
1O-3
-
1.5
x 1o
-3
-
4.6
x lo
-’
29.3
2.
4 x l
o-’
25.6
2.
7 X
lC?
22.0
1.
3 x
1Cr5
33
.4
5.3
x 1o
-3
_
2.8
x 1O
A
29.1
22
.8
1.4
x 10
-l 24
.3
19.2
3.
7 x
lo-’
20
.4
8.2
4.8
29.6
44
7.6
x lo
-’
5.9
x 1o
-3
64
3.2
x lo
3 1.
2x
lo4
1.2x
lo
4 5.
3 x
lo3
9.0
x 1c
r3
5.6
x 10
-l 7.
0 5.
9 x
lo-3
64
3.
2 X
lo3
7.
2 x l
o-6
3.5
x 1o
-5
1.2
x 1o
-3
1.2
x l@
4.
3 x
lo4
7.0
x 10
-s
1.3
x 1o
-3
4.9
67
3.7 1.6x
lo
-“
0.10
-0.0
50
12.7
-13.
0 N
aOH
4.
6 X l
p
15.8
(18.
5)
T; 9
5%ci
s pr
od.
14.9
- - 17
.3
28.2
25
.4
- - 33.6
18
.4
3.6
31.2
-
33.3
34
.3
31.8
38
.0
- -
22.6
33
.3
23.6
39
.3
- -
24.3
40
.0
23.3
10
.3
22.2
14
.8
23.1
22
.8
31.8
38
.0
- -
22.6
33
.3
28.0
11
.9
- -
_ - -
- - -
27.8
21
.4
22.6
20
.6
22.8
26
.3
23.8
23
.9
30.0
24
.7
31.3
31
.2
S S,T;
55
% c
is p
rod.
T;
10
0%
cis
prod
. T;
67
% c
is
prod
. T T;
45-
55
% c
is p
rod.
T;
65-
70
% c
is p
rod.
T T T;
cis
pro
d.
s;
coo
S, P
nl
S; T
he
rate
co
qst.
refe
rs
to t
he
form
atio
n of
cis
- C
o(en
),(O
H)o
x S S;
100
%
trans
pr
od.
S; 1
00%
tr
am
prod
.
S T S ; 3
0 %
tra
ns p
rod.
S T;
95%
tr
ans
prod
. T;
95
% t
rans
pr
od.
S T;
100%
tr
ams
prod
. T;
11
%
trans
pr
od.
T; 6
% t
rans
pro
d.
T;
10%
tr
ans
prod
. S;
30%
tr
ans
prod
. S T;
95
% t
rans
pro
d.
T T S,T
T T T T; 5
% t
rans
pr
od.
T;
100%
tr
ans
prod
. T;
10
0%
tran
s pr
od.
T; 9
4%
tran
s pr
od.
T; 8
5-90
%
tran
s pr
od.
T; 8
5-90
%
tram
pr
od.
243
IF _.
245
%
138
&
242
k 24
0 G
F 23
6 2
241
3 24
2 9 c:
24
1 S’
237
243
B
145
g B
244
5 36
2 s 2 6
363
5 33
3 33
3
346
236
237
128
240
240
128
240
129
240
240
237
128
240
236
241
138
242
241
242
243
164
166
240
236
241
2
DA
TA
TAB
LE
IV.
(Con
t.)
e
Com
plex
/W
) PH
M
ediu
m
k A
H+
AS*
C
omm
ents
truns
-Co(
en)Z
N3C
lf 0.
0050
11
.7
NaO
H
rran
s-C
o(en
),(N
j)z+
trans
-Co(
en)z
(N3)
NC
S+
trans
-Co(
en),(
NC
S)C
l+
fran
s-C
o(en
)z(N
CS)
NO
Z+
tram
-C
o(en
)z(N
CS)
N3f
tra
ns-C
o(en
),(N
CS)
z+
trans
- C
o(en
)z(O
CO
CH
3)C
l+
fran
s-C
o(en
)z(O
CO
CH
3)2+
tru
ns-C
o(en
)z(O
CO
Ph)C
l+
trans
-Co(
en)2
(OC
OPh
)2+
trans
-Co(
Me-
en),C
l,+
trans
-Co(
Et-e
n),C
l,+
trans
-Co(
d,l
-pnX
C12
+ tra
ns-C
o(d,
l-bn)
zC1z
f tra
ns-C
o(m
eso-
bn)2
C12
+ tra
ns
-Co(
teta
)Cl,+
0.02
5 -
O.O
018~
.002
l 0.
050-
0.10
- 0.
033-
0.10
0.
1 0.
014
0.1
0.00
27
_ - - _ _ 0.20
NaO
H
_ NaO
H
NaO
H
12.4
- 11
.3
12.7
-13.
0 - 12
.5-1
3.0
1.3-
2.3
12.0
2.
0-2.
3 11
.3
-
NaO
H
Na(
ClO
.,,O
H)
NaO
H
Na(
C10
4,0H
) N
aOH
-
- - _ 5.74
.8
_
trans
-C
o (t
runs
-14-
dien
e)C
lz’
0.20
trans
-Co(
cycl
am)C
lz+
0.1
truns
-Co(
cycl
am)(
NO
Z)C
l+
0.3
trans
-Co(
cycl
am)(
N02
)Br+
0.
05
trans
-Co(
cycl
am)(
NC
S)C
l+
0.25
Ru(
NH
&C
l’+
0.00
2
6.0-
6.8
_ 8.4-
9.4
2,6-
lutid
ine
buff
er
HN
OJ2
,6-lu
tidin
e bu
ffer
Li
NO
a B
orax
bu
ffer
7.2-
8.0
_ 11.3
-11.
7
Ru(
NH
~)sC
?+
Ru(
NH
3)5B
rZ+
Ru(
NH
&B
r?+
- - 0.00
1
0.00
2
- -
11-1
2.1
y-co
llidi
ne/H
NO
, bu
ffer
y-
colli
dine
/HN
03
buff
er
NaO
H
+ CH
3-@
S0,N
a
NaO
H
11-1
2.1
11.0
-11.
4 N
aOH
N
aOH
+
CH,+
SO,N
a
Ru(
NH
&I*
+ 11
.0-1
1.3
NaO
H
+ CH
,-@SO
,Na
cis
-Ru(
en)&
’ ct
i-Ru(
en)z
Br2
+ 11
.3-1
2.0
10.0
-
4.1
x 10
-l
(0°C
) 1.
1 x
lo-*
2.
2 x
lo-3
13
2.
0 x
lo4
3.3
x 1K
3 6.
6 x
1o-3
11
5.
1 x
lo-z
7.
8 3.
2 x
lo-*
1.
2 x
lo4
1.6x
lo
4 2.
5 x
1O-3
2.
3 x
lo3
1.0x
lo
4 5.
7 x
lo5
(19.
8”C
) 2.
2 x
lo5
(19.
8”
C)
6.7
x lo
4 7.
6 x
lo*
(26.
9”
C)
1.0x
lo
4 (2
2.3”
C)
8.9
x 10
’
5.2
26.7
34
.2
5.0
(24.
6”
C)
18
11.7
5.3
Fast
(0
” C
) -
-
Fast
(0
” C
) -
-
- _
_ -
- -
22.6
22
.3
- -
_ -
33.6
44
.2
22.6
22
26
.3
23
24.8
28
_
-
23.3
38
.3
22.6
36
.5
23.6
36
.2
24.2
38
.0
24.0
40
.4
- -
_ -
_ _ - _
_ -
21.1
25
- -
- 22.5
- 21.8
23.7
24
.2
Tabl
e R
ef.
No.
-
S,T;
87
%
tran
s pr
od.
138
ST;
70%
tr
ans
prod
. 13
8 T;
60-
90%
ci
s pr
od.
242
S; 2
6%
tran
s pr
od.
165
T 24
1 T;
70%
ci
s pr
od.
242
T; 4
0 %
tra
ns p
rod.
23
7 SS
F; 8
0 %
tra
ns p
rod.
32
3 T;
10
0%
trun
s pr
od.
243
S SF
323
T 24
5 TF
24
6 TF
24
6 TF
24
3 TF
24
6 TF
24
6 S
247
S S &r;
100%
tra
ns
prod
.
Sap;
100
%
tran
s pr
od.
S ST
247
168
348
348
s
346
P
S S; P
relim
inar
y va
lue
S, T
S, T
180
5 24
8 $ 3 s
248
S, T
S,
T
248
9 9 24
8 8.
Rh
(NH
&C
l’+
Rh
(NH
a)sC
l’+
Rh
(ND
a)5C
l’+
Rh
(NH
a)sB
r’+
R
h(N
Ha)
sBt+
R
h(N
D3)
sBr2
+
Rh
(NH
a)sI
’+
Rh
(NH
&I*
+
Rh
(ND
&‘+
Rh
(NH
&N
3*+
R
h(N
Ha)
sON
O’+
R
h(N
H&
OS
Oa+
R
h(N
H&
OC
OH
’+
Rh
(NH
&O
CO
CH
3’+
R
h(N
Ha)
s(O
CO
CH
zF)‘+
R
h(N
H&
OC
OC
HF
#+
Rh
(NH
&(O
CO
CF
a)2+
R
h(N
H~
)&K
OC
Cla
)Z+
Ir
(NH
a)sC
I*+
Ir
(NH
3)5B
f+
Ir(N
H,)
,B?’
Ir
(NH
,)sI
”
Ir(N
H,)
sON
O,‘+
Ir
(NH
3)50
CO
CF
32+
0.00
4
0.04
0 11
.4-1
2.0
0.1
O(e
xt.)
0.
1
0.1
O(e
xt.)
0.
1
0.1
O(e
xt.)
0.
1
0 1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
O(e
xt.)
- O
(ext
.)
O(e
xt.)
1.0
1.0
11.7
-12.
0
- - - - - - - _ -
12.0
-13.
3 N
a(C
104,
0H)
12.8
-13.
0 N
a(C
lO,,,
OH
) 12
.0-1
2.4
Na(
Cl,
OH
) 13
.4-1
3.7
Na(
Cl,
OH
) 13
.4-1
4.0
Na(
Cl,
OH
) 12
.7-1
3.4
Na(
Cl,
OH
) 12
.0-1
2.7
Na(
CI,
OH
) 12
.5-1
3.3
Na(
CI,
OH
) 12
.5-1
2.7
NaO
H
- n
one
12.5
-12.
7 N
aOH
-
NaO
H
13.0
-13.
9 N
a(C
lO.,,
OH
) 1.
9x
1P
31.0
19
12
.0-1
2.7
Na(
CI,
OH
) 5x
10-4
-
-
NaO
H
+
CH
,@-S
O&
0.5
- -
S,
T;
100%
ci
s pr
od.
NaO
H
+
CH
,-@
SO
,Na
1.42
20
.3
10.3
S
, T
; 10
0%
cis
prod
.
Na(
C10
4,0H
) 1.
09 x
lo-
4 27
.5
15.6
N
aOH
4.
1 x
lo-4
27
.9
19.5
N
a(C
104,
0D)
1.8
x 1O
A
25.6
9.
8
Na(
C10
4,0H
) 9.
6 x
lO-’
29.5
22
.1
NaO
H
3.5
x 10
-4
30.0
26
.1
Na(
C10
4,0D
) 1.
6 x
lK-’
26.3
12
.9
Na(
C10
4,0H
) 2.
3 x l
o-’
31.8
27
.0
NaO
H
7.3
x 10
-s
32.2
30
.8
Na(
C10
4,0D
) 3.
1 x
1o-5
29
.0
18.2
3.1
x lo
-’ 34
.0
25.8
1.
8 x
lo-’
27.5
26
1.
3 x
10-3
24
.5
10
3.6
x lO
d 33
.2
28
2.1
x 10
-6
31.9
22
1.
3 x
1o-s
31
.9
26
5X10
A
30.1
22
1.
0 x
1tP
18
.0
-12
3x10
4 26
.4
14
4.8 x l
p 33
.2
19
1.1
x 1o
-9
22.5
-2
4.1
2.2
x 1P
34
.6
22
8.3 X 1
O-9
35
.7
24.2
T
S
S;
DzO
as
sol
ven
t,
10”
ran
ge
T
S
S;
DzO
as
sol
ven
t,
10”
ran
ge
T‘
S
S;
DzO
as
sol
ven
t,
10”
ran
ge
S
S
S
S S
S S
S;
OC
su
gges
ted
S;
OC
su
gges
ted
T
R
S
S
S
S
248
P
_.
% h
248
a B z R
186
3 24
9 2 E
: 33
9 S
’
186
B
249
%
B
339
a
186
5
249
2 6 33
9 k 2
250
160
102
251
251
251
251
251
251
340
192
9 34
0 25
3,
340
160
251
84 J. 0. Edwards, F. Monacelli and G. Ortaggi
no clear variation with central metal ion. It is indeed obvious that the values from experiments agree not at all with the estimates for the first mechanism and are in very good agreement with the estimates available for the second mechanism.
Rate constants and activation parameters for the base-catalyzed process for aquocomplexes (M = Cr, Fe) are more frequently expressed in the literature in terms of the rate law
R = k_r[H+]-‘[complex]
In such cases the data reported in Data Table IV have been changed to conform to the rate equation
R = k,[OH-] [complex]
by use of the values K, = 1.0 X 10-‘4Mz, AH” = 13.5 kcal mar’ and AS” = -19.3 cal mar’ deg-’ for the process
Hz0 # OH- + H+
For these aquocomplexes the formation of a con- jugate base through the dissociation of an acidic co- ordinated water is quite obvious and it can be readily seen that when interpreted according to the rate law R = kz[OH-][complex] the experimental data lead to d S* values which fall into the range expected for a conjugate base mechanism. This result lay unrecognized among the data available during the long and heated discussion of the base hydrolysis mechanism.
9. Leaving Group Effects
If the solvation entropy of complexes ML5XZ+ is less dependent on the nature of the leaving ligand X- than is the solvation entropy of the free ligand, then one might expect to see a part of this difference in the dS* values when a substitution mechanism is pre- dominantly dissociative. Taking as examples of X- the halide ions, we would expect to see the lowest value (e.g., the most negative or the least positive) of dS* for F and the highest value for I-. Some data which show this trend are presented in Table IX. These are
.base hydrolysis reactions involving the pentaammine- halo complexes of four different cations.
TABLE IX. Activation Entropies for Base Hydrolysis of some Halocomplexes.”
Complex F cl- Br- I-
Cr(NH3)5XZ+ - 6.2 +16.5 +22.5 +26.8 Co(NH3)gXZ+ +20.4 +34.s +37.7 +42.6 Rh(NH&X*+ - +19.5 +26.1 +30.8 Ir(NHj)5XZ+ _ +19 +22 i24.2
a These data are taken from Data Table IX.
A similar variation of dS* values should appear in the aquation reactions of Data Table I. Although it is not always as clear (as a consequence of the already mentioned scatter of experimental activation data), the expected trend is seen for aquations of Cr(Hz0)5 X2+ (except for F which very likely has a different hydrolysis mechanism), Ru(NH~)~X*+, cis-Ru(en)z (HzO)X*+, and Rh(NH3)5X2+.
We deem it important to reiterate here that ideas presented in this review are not necessarily original with us. The correlation of entropies of activation with ground state entropies of free ions in solution has been discussed often,*’ and the relation of this to solvation is expected. Nevertheless, the generality of this entropy correlation is made clear by the data summarized here.
10. Isomerization
The change in configuration of an octahedral com- plex can be related to the lability of the complex towards ligand substitution. Complexes which are labile to substitution tend to be labile to isomerization as well. Also isomerization rates decrease as crystal field stabilization energy in the ground state increases; for example, isomerization rates for cobalt and chro- mium complexes are measurable but there is little or no evidence for isomerization in the more inert rhodium and iridium complexes.
Isomerization may be a direct consequence of a ligand substitution mechanism; a clear example of this is seen in the mechanistic postulations of Nordmeyer24b for chloropentaaminecobalt(II1) base hydrolysis. In other cases, isomerization may proceed by a mechanism unrelated to a replacement; the “Bailar twist” me- chanism29 is an example.
In Table X, a set of data for hydrolyses of cobalt and rhodium complexes with chloride ion as leaving group is reported. The striking thing about these numbers, mostly collected by Tobe, 3o is that a positive entropy is accompanied by a considerable steric change @runs- reactant goes to cis -product). When the value of d S* is negative, only lrans-product (i.e., retention of con- figuration) is obtained.
It is reassuring therefore to see that the numbers in Data Table V on isomerizations (leaving out oxalate complexes, of course) show predominance of positive entropy values. One can conclude that, in order for an isomerization to occur, considerable loosening of the metal-ligand bonding must take place. Such a loosen- ing is expected to decrease bond force constants for both stretching and bending modes and thus to in- crease the entropy of the reacting system.
It is interesting to observe that for the truns-cis iso- merization of the complexes Co(en),(OH,)X’+, the values of dS* are always positive and fall generally in the range from +lO to +20 cal mot’ deg-’ (see
DA
TA
TAB
LE
V.
Isom
eriz
atio
n.
Com
plex
PH
M
ediu
m
k dH
* dS
*
0.20
truns
-Cr(
OH
2)4C
l2
+ 0.
20
cis-
Cr(
en)z
(OH
h+
cis-
Cr(
en),(
OH
2h3+
tru
ns-C
r(en
h(O
Hh+
tru
ns-C
r(en
)Z(O
Hz)
23+
trans
Cr(
en)~
(DM
SO)C
l*+
truns
-Cr(
en),(
DM
SO)B
?+
truns
-Cr(
en)Z
(DM
S0)~
3+
rrun
s-C
r(en
)z(D
MSO
)~3+
rr
uns-
Cr(
ox)Z
(OH
)23-
tru
ns-C
r(ox
)2(O
Hz)
OH
Z-
truns
-Cr(
ox)z
(OH
&-
trans
-Cr(
oxh(
OH
2);
truns
-Cr(
ox)2
(OH
2)z-
trans
-Cr(
ox)z
(OH
&
trans
-Cr(
oxh(
OH
z)z-
truns
-Cr(
mal
)Z(O
H)2
3-
truns
-Cr(
mal
)z(O
H2)
OH
*-
trans
-Cr(
mal
)2(O
Hz)
z-
truns
-Cr(
mal
)n(O
H2)
Z-
aBR
-Co(
tetre
n)N
CS*
+
cisC
o(N
H&
(0H
&~~
+ H
z0
cis-
Co(
NH
&(0
H2)
NO
z2+
Hz0
cis-
Co(
en)z
Clz
+ -
Hz0
ci
s-C
o(en
)Xlz
+ _
TMS
cis-
Co(
en)2
Clz
+ -
MeO
H
0.10
0.
01
0.10
0.
01
- - _ 0.10
0.
10
1.0
0.10
0.
10
0.10
1.
0
1.4
0.7
HC
104
0.7
HC
l04
10.9
-11.
4 en
-LiC
IOd
2.0
HC
I 10
.9-l
1.4
en-L
iC10
4 2.
0 - _ - - -1
2 -8
3.
0 1.
8-4.
4
-12
7-9
1.0-
3.0
2.8
2.15
-2.4
HC
l D
MSO
D
MSO
D
MSO
D
MSO
N
a(C
104,
0H)
Na(
ClO
.,,O
H)
(H,N
a)C
lO.,
_ 50 %
(w
)HzO
- A
ceto
ne
50%
(w
)HzO
- D
ioxa
ne
50%
(w)H
~O-
Met
hano
l 5O
%(w
)H20
- Et
hano
l 5O
%(w
)HzO
- Is
opro
pano
l N
a(O
H,C
lO.,)
N
a(O
H,C
lO.,)
(N
a,H
)C10
4 Li
C10
4
Na(
CI0
4,N
CS)
C
H,C
OO
H
6.2
x 1o
-5
(34.
8”C
) 7.
8 x l
o-5
(34.
8”
C)
1.0x
10
” 2.
9 x
1F5
5.1
x lO
A
2.2
x 1P
(2
.6
x 10
4)
(2.5
x
lOA
) (3
.0
X 1
0-6)
(9
.0
x l@
) 1.
9 x
1o-z
2.
0 x
lo-3
5.
9 x
lo4
4.2
x lo
4 6.
5 x
10-s
6.2
x 1O
-5
1.0x
1t
P
7.8
x lo
-’
9.7
x l(r
5
2.5
x lC
? 1.
4 x
10-3
1.
8 x
lOA
1.
8 x
lOA
3x1@
2.7
x lo
4 8.
3 x
10d
(30”
) 1.
9 x
1o-5
(1
.2
x 10
-y
5.3
x 10
-s
- _
S
_ -
S
31.4
19
.4
_ -
26.4
5.
8 -
-
23.2
2.
9 23
-7
22
-1
0 21
.9
1.0
13.8
-2
0.3
14.0
-2
3.9
17.9
-1
3 17
.5
-15.
3 -
-
S S S S S S S S S S S S; o
x on
e en
d di
ssoc
iatio
n S
x 3 26
3 3”
B
26
3 3’
B
262
g 54
b
262
2
54
5 36
7 d
366
6 36
6 5
367 70
70
26
5 26
4 36
8
- -
S 36
8
_ -
S 36
8
- _
S 36
8
- -
S 36
8
17.9
-1
5.1
24.3
9.
9 31
.8
21.5
28
.7
11.3
30.3
6
S S S S; N
Oa-
incr
ease
s k
S; f
ast
exch
ange
of
H o
n N
H
grou
p;
NC
S is
N-
bond
ed;
isom
eriz
atio
n to
th
e ag
.S
form
70
70
70
330
283
24.4
(7
.0)
- -
256
256
(41.
1)
57.8
25
.0
- 6.
4 _
-
S S S S s;
35”
261
267
133
Z
Com
men
ts
Tabl
e h
Ref
. N
o.
.$ s
DA
TA
TAB
LE
V.
(Con
t.)
Com
plex
cis-
Co(
en)*
Cl*
+
cis-
Co(
en)*
Cl*
’
cis
-Co(
en)*
Cl*
+ ci
s-C
o(en
)*C
l*+
cis-
Co(
en)*
Br*
+ ci
s-C
o(en
)*(O
H*)
Cl*
’ ci
s -C
o(en
)*
(OH
*)C
l*+
cis-
Co(
en)*
(OH
)*+
cis
-Co(
en)*
(OH
)*+
cis-
Co(
en)*
(NH
*)O
H*’
ci
s -C
o(pn
)*C
l*+
cis
-Co(
pn)*
Cl*
’
cis-
Co(
pn)*
Cl*
+
tram
-C
o(en
)*C
l*+
trans
-Co(
en)*
Br*
+ W
zns-
Co(
en)*
(OH
)*’
- 1.0
_ TM
S _
DM
A
13.7
N
a(N
O,,O
H)
trans
-Co(
en)*
(OH
)*+
(unc
ontr)
>7
tra
ns-C
o(en
)*(O
H)*
+ 2.
5 14
tr
ans-
Co(
en)2
(OH
)N02
+
- -7
trans
-Co(
en)*
(0H
)NH
3*+
truns
-Co(
en)*
(OH
)NH
3*+
trans
-Co(
en)*
(OH
*)C
l*+
truns
-Co(
en)*
(OH
*)C
l**
trans
-Co(
en)*
(CH
30H
)Cl*
+ tra
ns-C
o(en
)*C
l(DM
F)*f
tra
ns-C
o(en
)*C
l(DM
SO)*
+
trans
-Co(
en)*
(OH
*)B
? fr
uns-
Co(
en)*
(OH
*)O
H*f
tru
ns-C
o(en
)*(O
H*)
*3+
- 0.01
2 0.
01
2.5
(unc
ontr)
(u
ncon
tr)
- _
EtO
H
_ _
n-Pr
OH
7.
26
x lo
+’
24.6
0.10
(u
ncon
tr)
0.01
0.
012
0.01
-0
-0
0.01
_ 0.
050X
J.10
1.07
tra
ns-C
o(en
)*(O
H*X
3+
0.8
PH
Med
ium
k
AH
* A
S+
- M
eOH
2.
2 x
1@
22.8
_ M
eOH
2.
2 x
1o-5
-
3.5
(-3.
3)
-
- Et
OH
_
- -
DM
A
1.92
H
CIO
,, 2.
0 H
NO
* 14
N
a(N
03,0
H)
>7
Na(
ClO
.,,O
H)
-11
Na(
N03
,0H
) _
MeO
H
1.7
x 10
” 9.
2 x
lo-6
(7.4
x
lo-‘
) 2.
6 x
lo-’
3.
6 x
10”
3.6
x lo
4 1.
8 x
lo6
2.38
x
lo-’
22.9
20
.7
22.5
26
.4
- - 28.9
_ 23
.3
1.0
x 1o
-5
23.9
(1.7
x
10-9
) - 7.
6 x
lo4
27.5
24
.5
_
3.4
-12
-
2 _ -
13.5
_
5.4
(-1.
5)
5.9
(-1.
2)
6.8
(0.5
) -
6.4
_ _
Na(
C10
4,0H
) N
a(N
O*,
OH
) se
lf-bu
ffer
ing
mix
ture
s
2.9
x lO
A
27.9
9.
7 1.
8X
lo-6
-
_
1.7
x lo
-’
_ _
10.2
-1
1 2.
0 1.
92
_ _ _
- Na(
N03
,0H
) H
N09
H
C10
4 M
eOH
D
MF
DM
SO
40.3
- 26
.6
26.4
25
.4
23.6
_
50.7
-
11.7
(1?.
8)
3.0
-
2.0
_ 1.3-
1.0
0 -
HN
03
Hz0
H
NO
*
2.1
x lo
+ 4.
3 x
lo+
7.1
x 10
” (1
.2
x 10
”)
1.2
x lo
-*
1.5
x lo
4 8.
5 x
1o-5
(3
7.6”
) 1.
63
x lO
A
3.0
x l@
1.
18~
lo-’
26.4
12
.7
27.5
22
.2
- -
(Na,
H)(
C10
4,N
Og)
6.
92
X l
p -
6.84
X
10”
- -
25.6
4
Com
men
ts
Tabl
e R
ef.
No.
S 26
8
S; V
ery
accu
rate
ra
te
cons
tant
S S;
2.9
<[Li
Cl]<
7.8
S S S nmr
S nmr
S
132
268
269
270
257
133
324
260
324
S 26
8
S 26
8
S 26
7 S
270
S; r
ate
cons
tant
is
dep
ende
nt
254
on
purit
y of
com
plex
S
260
nmr
324
S; i
ntra
mol
, re
arra
ng.
258
S 10
6
nmr
324
S 13
1 $
S 25
7 e
S 26
6 P
S 20
5 S
205
S 13
6 S
131
S; R
ate
cons
tant
is
25
4 de
pend
ent
on
purit
y of
co
mpl
ex
S 25
5 S
125
trans
/Co(
en)z
(OH
z)N
32+
0.01
rr
ans-
Co(
en)z
(OH
z)N
022+
-
trans
-Co(
en),(
OH
z)N
CS’
+ -
0.28
-2.1
6 tra
ns-C
o(en
)2(0
Hz)
NH
a3+
0.1
1.22
tra
ns-C
o(en
)2(O
Hz)
(OC
OC
H3)
Z+
0.1
1.04
.5
trans
-Co(
dipy
)2(O
Hz)
N0~
2+
2.5
0.2-
2.5
cis,c
is-C
o(en
)(N
Ha)
2(O
H)z
+ -
10.3
tra
ns,c
is-C
o(en
)(N
H~)
2(0H
)z+
_ 10
.3
trans
-Co(
en)(
NH
a)2(
OH
)z’
- 10
.3
trans
-RR
&S-
Co(
2,3,
2-te
t)(O
Hz)
Cl*
+ 0.
014
2.0
2.0
l-3.6
H
Cl0
4 - (N
~,H
)cI~
~ (N
a,H
)C10
4 (N
a,H
)NO
s N
a(C
l,OH
) N
a(C
l,OH
) N
a(C
l,OH
) H
ClO
z,
7.3
x 1o
-5
1.7
x lo
-’
6.5
x lo
-’
1.8
x lo
4 2.
4 x
10-s
3.
4 x
lo4
4.3
x 10
-s
1.0
x 1o
-5
3.5
x 1o
-5
3.8
x 1O
-3
_ _
S 32
.8
S; I
ntra
mol
ecul
ar
rear
- ra
ngem
ent
sinc
e th
e O
H
form
ha
s id
entic
al
rate
26
.8
3.1
S 33
.3
(17.
8)
S 26
.9
11.1
S
32.9
17
.7
S -
- nm
r ; t
ram
, tr
ans
prod
. -
- nm
r; ci
s, c
is p
rod.
_
- nm
r; ci
s, c
is p
rod.
_
- S
138
258
165
106
2.59
16
9 32
4 32
4 32
4 15
2
DA
TA
TAB
LE
VI.
Liga
nd
Isom
eriz
atio
n.
Com
plex
P(
M)
PH
Med
ium
k
dH*
dS*
Com
men
ts
Tabl
e R
ef.
No.
Cr(
OH
z)$S
CN
2+
cis
+ t
rans
-Cr(
H,0
)4(N
CS)
(SC
N)+
Co(
NH
s)sO
NO
’+
Co(
NH
&O
NO
’+
cis-
Co(
NH
s)4(
0H2)
0NO
Z+
cis-
Co(
NH
~)~(
ON
O)O
N02
+
bans
-C
o(en
)Z(N
CS)
ON
O+
Rh(
NH
&O
NO
*+
Ir(N
HX
)50N
02+
1.0 1.0
- - - _ _ - -
1.92
o-1
- - - - - - -
(Na,
H)C
104
(Na,
H)C
lOd
Hz0
H
z0
Hz0
Hz0
Hz0
H
z0
Hz0
4.2
x 1O
-5
8.3
x 10
-s
3.2~
10
-s
3.3
x 10
” 3.
8x10
-6
(30”
) 2.
5 x
lo-4
1.5
x lO
A
9.6
x lo
4 4.
4 x
lo-5
23.5
1.
0
19.6
-
9.8
21.9
-
5.6
22
-5
- -
7.7
-49
22.7
-
8.9
18
-12
19
-14
S;dS
* =
0.3
if aq
uatio
n 18
an
d is
om.
proc
eed
thro
ugh
diff
eren
t tra
nsiti
on
stat
es
S; S
CN
- fro
m
S- t
o N
- 33
1 bo
nded
S
284
S; I
ntra
mol
. re
arra
ng.
285
S 25
6
S; t
he
final
pr
oduc
t is
cis
- 25
6 C
o(N
H&
(NO
z)z+
S
184
S; I
ntra
mol
. m
ech.
28
5 S;
Int
ram
ol.
mec
h.
285
2
88
TABLE X. Activation Parameters and Steric Courses of the Reactions” mans-(MLACI)“+ + H,O-+ (MLAH20)“+’ + Cl-.
M L A dH* dS* % steric change
co (enk OH 25.6 +14.6 75 co (en)2 Cl 27.5 +13.1 35 co (en)2 Br 24.6 + 4.1 50+5 co (enk NCS 29.8 + 7.8 60flO co SS-trien Cl 25.4 +15.3 100 co RR,SS-2,3,2-tet Cl 25.9 +12 50+20 co (en)2 N3 20.7 - 6 0 co (en)2 NH3 23.0 -11 0 co (en)2 CN 22.0 - 3.4 0 co (en)2 NOz 20.9 - 2.2 0 co cyclam OH 18.8 - 4.2 0 co cyclam Ci 24.3 - 4.3 0 co RS-2,2,2-tet Cl 24.3 + 1 0 Rh en, Cl 24.7 - 9 0 Rh en2 Br 23.2 -11.7 0 Rh en, I 21.1 - 7.5 0
a The values of dH* quoted in this table are generally reli- able to better than 50.5 kcal mol” and the dS* to better than +1.5 cal mol-’ deg-‘. The numbers in this table have been taken from Data Table I wherein original sources are given.
Data Table XIV). We estimate that the contribution to AS* from the dissociation of a water molecule should be near to +7 cal mar’ deg-‘. This seems to suggest that the isomerization proceeds through a dissociative mechanism involving cleavage of the metal-water bond and subsequent rearrangement of the pentacoordinate complex. Owing to the fact that some degrees of freedom not present in the octahedral reactant are acquired by the pentacoordinate inter- mediate, the observed dS* values are in agreement with the dissociation of a bound water.
A dissociative mechanism is also consistent with the postulation that, in the hydroxo complexes Co(en)z (OH)z+ and Co(en),(OH)(NH3)‘+, the isomeriza- tion involves dissociation of one end of the ethylene- diamine chelate link.
TABLE XI. Isomerization Reactions of truns-Cr(AA)2XY.a~b~c
J. 0. Edwards, F. Monacelli and G. Ortaggi
There are some interesting observations on the isomerizations of anionic chromium complexes with oxalato and malonato ligands. The relevant numbers are given in Table XI. The differences in AH* and AS’ are large enough to signal a change in mecha- nism.
One possible explanation is that the oxalate com- plexes isomerize through a cleavage of the chelate ring assisted by solvent water molecules. The negative values of AS* led to the suggestion of water participa- tion and this recently has been supported by the activa- tion volume of the reaction (see Data Table XX).
For malonato complexes, the high values of AH* and the positive values of AS* (when one ligand is water) suggest that the isomerization proceeds through dissociation of a coordinated water molecule or spon- taneous opening of the chelate ring without any parti- cipation of the solvent. However, the observation that tram- Cr (mal), (OH)2- shows activation parameters analogous to the oxalato complexes and the considera- tion that the malonato six-membered ring should be more inert than the five-membered ring indicates that the mechanism involving dissociation of the water molecule is to be preferred.
11. Ligand Isomerization
The change in point of attachment of a ligand at the ligand-metal bond is a matter of considerable interest because the factors which govern the position of bond- ing, as in the case
M-O-N a=E U-N /O
‘0 ‘0
are not at all clear. For thiocyanate ion, isomerization in both directions is accompanied by a positive entropy, suggesting metal to Iigand loosening in the transition state. By way of comparison, isomerization of nitrito complexes to the nitro form (as in the equation above) occurs with a negative value of AS*. This suggests
that the transition state is more restricted in conforma- tion than is the reactant. A configuration such as
OX ma1 mal-ox
Complex dH* dS* dH* AS+ 6AH* 6AS’
Cr(AAMHz0)2- 17.9 -13 31.8 +21.5 13.9 +34.5 Cr(AA),(OH)(H20)*- 14.0 -23.9 24.3 -4 9.9 10.3 +33.a Cr(AA)Z(OHh3- 13.8 -20.3 17.9 -15.1 6 + 5.2
a The symbols are defined as follows: ox = oxalate, ma1 = malonate, AA represents both of the bidentate ligands, and X and Y represent HZ0 and/or OK. ’ The reaction is tram to cis isomerization. ’ Data taken from Data Table Ref. 70.
L&and Replacements in Octahedral Complexes 89
the prime interaction is between metal atom and nucleophile. This is usually the case (albeit the inter- action may be weak), but there are unquestioned ex- ceptions. For example, the reaction
Co(NH&0COR2+ + OH- # Co(NH&0H2+ + RC02-
can proceed by direct nucleophilic attack on carbonyl carbon as well as by attack at metal or as by SNICB mechanisms. The distinction between the possibilities can be made by an isotope tracer experiment, for the bimolecular reaction of the equation above with la- beled hydroxide ion would yield labeled acetate and unlabeled CO(NH~)~O~~“. The alternative mecha- nisms (&lCB and direct displacement on cobalt) would yield unlabeled acetate and labeled complex. Electronic effects and activation entropies also are helpful in making these mechanistic assignments.
The alkaline hydrolysis of cobalt(II1) carboxylato complexes has a complicated rate law with one rate term of form
for the transition state is possible. The available data are presented in Data Table VI.
12. Racemization
Coordination compounds with three bidentate ligands (or with related configurations) can exist in optically-active forms. Thus, for example, it is possible to have a D-Cr(ox)J3- and L-Cr(oxX3-. The race- mization process (which is a type of isomerization) leads to the d,l-mixture. This process can occur more rapidly, at the same rate, or more slowly than ex- change of ligands with those in the surrounding me- dium. Some data on the racemization process for a variety of complexes are given in Data Table VII.
With one significant exception, the data are too limited to allow worthwhile discussion. The exception is the group of chromium(II1) oxalate complexes. The activation entropies are very close to those for cis-truns
isomerization of chromium(II1) oxalate complexes. This suggests a common mechanism for racemization and isomerization. A possibility might be as follows:
1- FI FI Cr(ox)l + H,O zr? bd2 jr-O-C-C-OH
OH
with the intermediate species able (a) to add water to the carbonyl group of the monodentate oxalate and accomplish hydrolysis, (b) to reform into the opposite optical form, (c) to add another oxalate and accom- plish exchange, etc. These mechanisms have been dis- cussed in some detail in the references given in the Data Table and also in reference 25a.
Some cobalt(II1) racemizations, including Co (ox)~~-, show positive values of dS* , whereas for the chromium complexes negative values have been found. This sharp difference in the entropy of activa- tion values can be explained on the basis of some recent studies of the exchange between water and the bound oxalato ligand.31 Although a definite mecha- nism for reaction of the cobalt(II1) complexes could not be offered, any mechanism such as that suggested for the chromium complexes (equation above) can be ruled out on the basis of the difference in d S* values alone.
Also the negative entropy values for racemizations of Cr(ox),(NN)- and COG+ complexes may involve attack of water at the carbonyl carbon (see next section and Data Table XVII).
13. Ambiguity in Site of Attack
When a nucleophile reacts with a coordination com- pound, it is generally assumed (often implicitly) that
v = k[Co(NH&0COR2+] [OH-]
For this term, the rate constants are similar to those for loss of other ligands from the cobalt coordination sphere and rather small electronic and steric effects are found.32,33 Study of the alkaline hydrolysis of the first displaced benzoato ligand in some trans-Co(en)2 Kxoc,H4x)2+ ions indicated that the Hammett equation is followed with a reaction constant Q of o.745.33c This is significantly less than the value of about +2 expected for OH- attack at carbonyl carbon. Mass spectrometric investigations of the benzoate product from base hydrolysis of Co(en)2(OCOAr)2+ in ‘“0 enriched water showed no enrichment there- in,33e thus the cobalt-xygen bond is cleaved in the reaction. The values of AS* observed for base hydro- lysis of cis- and trans-Co(en)2(OCOCH3)2+ are the +18.4 and +22.4 cal moT’ deg-‘;33g the sign and magnitudes are fully consistent with the SNICB me- chanism.
When the carboxylato ligand has a strong electron- attracting group attached to the carbonyl center, a second rate law term is observed and a new mecha- nism intrudes. The complex CO(NH~)~OCOCF~~+ hydrolyzes with the la:v
v = {k,[OH-] + k2[OH-]2}[Co(NH3)s0COCF32+]
with the new term being second-order in base con- centration. For the first term, values of 22.7 kcal mar’ and +lO cal mar’ deg-’ were obtained for AH* and AS*, respectively; again these are con- sistent with the SNICB path. For the second term, the respective values are 6.8 kcal rnor’ and -37 cal mar’ deg-’ which suggest considerable bond formation. Tracer studies showed that the kl path takes place with cobalt+xygen bond breaking and the k2 path
DA
TA
TAB
LE
VII
. R
acem
izat
ion.
8
Com
plex
/#
-‘)
PH
Med
ium
k
AH
”
Cr(
ox)X
3-
Cr(
ox)a
3-
CU
-Cr(
ox)Z
(OH
,),-
cis-
Cr(
ox)z
(OH
z)z-
C
r(ox
),(en
)-
Cr(
ox),(
dipy
)-
Cr(
ox)*
(dip
y)-
Cr(
ox)z
(dip
y)-
Cr(
ox)&
ipy)
- C
r(ox
),(ph
en)-
C
r(ox
)Z(p
hen)
- C
r(ox
)Z(p
hen)
- C
r(ox
),(ph
en)-
C
r(ox
)(en
),+
Cr(
ox)(
bipy
)Zf
Cr(
ox)(
phen
)z+
(+)f
rans
-Co(
dien
h (?
)
I-ci
s-C
o(en
)zC
lz+
0.00
24.0
9 -
(+)-
cis-
Co(
en)2
(NH
3)0H
Z3’
_ 1.
0 (+
)&-C
o(en
)zC
l(OH
z)Zf
0.
012
1.92
(+
)-C
oED
TA-
_ 2-
4
1
co(o
x)33
-
Rh(
ox)a
”-
0.54
0.
4-7.
0 (N
a,H
)ClO
., 8.
7 x
lO-’
23.3
*
Rh(
oxh-
0.
54
0.4-
7.0
(Na,
H)C
104
2.8
X l
o4
26.8
+
5.8
_ -
1.0
0 _
2.5-
l 1.
0 2.
6-7
1.0
_ 0.1
0.9
- 0.1
0.9 1.0
1.0
1.0
1.0
2.0
0 _ 1.0
14
- 1.0
14
0 0 0 0 7.1-
8.27
Hz0
H
ClO
., H
ClO
, (H
,Na)
C10
4 H
z0
HC
I H
z0
HC
l K
OH
H
z0
HC
l K
OH
H
Cl
HC
l H
Cl
HC
l N
aN03
+
HN
OX
, co
llidi
ne
buff
er
MeO
H,
LiC
l H
ClO
., H
ClO
, H
NO
a +
nitra
tes
Hz0
H
Cl
3.1
x lO
A
1.4
x lo
-*
3.3
x 10
4 4.
3 x
lo4
2.1
x 10
” 5.
3 x
lo4
2.1
x l@
2.
3 x
lo”
1.3
x 1o
-3
2.3
x lo
4 3.
0 x
lOA
1.
6 x
1O-3
6.
4 x
lo4
1.7
x 10
-s
3.2
x lo
-’
2.1
x 1o
-5
62
3.6
x lo
-’
2.1
x lo
4 1.
4 x
lo6
4.0
x lo
-r2
2.9
x lo
@
1.8
x lo
-5
1.9x
1O-5
AS*
15.2
- 13
.4
13.4
15
.2
17.8
15
.5
17.1
15
.3
17.4
17
.3
15.2
17
.7
20.5
19
.0
19.8
23
.5
-23.
7 - -2
8 -2
9 -1
9.8
-13.
8 -2
4 -2
1(-1
8)
-19
-17
-17
-21
-13.
7 -1
2.0
- 14
.5
-13.
6 29
22.0
21
.7
26.1
40
.0
25.4
28
.1
- 5.
1
(4.7
) 2.3
20.6
(2
3.5)
6.
0 14
.1
26.5
8.
8
Com
men
ts
Tabl
e R
ef.
No.
PM
27
2 PM
29
7 PM
27
5 PM
21
6 PM
27
2 PM
27
3 PM
27
4 PM
27
4 PM
27
4 PM
27
4 PM
27
4 PM
27
4 PM
27
3 PM
; k
incl
udes
aq
uatio
n 28
1 PM
28
1 PM
28
1 Ph
i; O
K
indu
ces
race
miz
.; 34
1 k
is 2
nd
orde
r (k
&
[OH
-])
rate
co
nsta
nt.
PM
282
PM
106
PM
257
P,;
Intra
mol
. re
arra
ng.
271
PM
272
PM;
’ th
e on
e-en
ded
344
4 di
ssoc
iatio
n is
ex-
P
elud
ed.
The
exch
ange
PM
‘ of
the
m
ore
labi
le
F (c
arbo
nyl)
oxyg
ens
B
hasA
H*
= 16
.3,
344
?
\ A
S”
= -
19.9
PM
34
2 Ph
i; H
+ in
duce
d ra
cem
iza-
g
342
tion,
k
is 2
nd
orde
r (k
,,,,/
$
[OH
-])
rate
co
nsta
nt.
&
a
Ligand Replacements in Octahedral Complexes 91
with carbon-oxygen bond breaking. The postulated mechanism is
“\‘a era \
(NH,),d+-0----C---OH=--OH--w tNH,),CoO+ + c
b
+H,O
0’ ‘fJ-
fulfilled,3’ for the values of kl change by a factor of 16 on going from Co to Rh and by a factor of 2 on going from Rh to Ir. On the other hand, the overall change in k2 values is less than a factor of two.
Some other possible examples of attack at carbonyl carbon include:
The base hydrolysis of a series of carboxylatopenta- amminerhodium(II1) complexes shows the same general behavior.35 If the R group of RCOO- ligand is H, CH,, CH*F, or CHF,, both the enthalpy and the entropy of activation related to the k1 path are virtual- ly insensitive to the nature of R and are in agreement with the SNICB mechanism. When R is a powerful electron-attracting group like CC& or CF,, both the enthalpy and the entropy of activation values are lower, as can be seen in Table XII.
a) Cr(NH3)50COCF3, aquation,dS* = -25; b) truns-Cr(ox)z(H20)OCOCH32-,‘aquation,
dS” = -18 8. . > c) trans-Cr(ox)z(OH)OCOCH33-, aquation,
AS* = -38.8; d) trans-Cr(ox)z(H20);, isomerization,
AS* = -14; and
This fact together with an observed deviation in an otherwise linear logkl versus pK, plot (where K, is the dissociation constant for the acid RCOOH) sug- gest a change in mechanism from the SNICB to a bimolecular attack on the carbonyl carbon of the carboxylato ligand. The dH* and d S* values of the kz path are consistent with the proposed termolecular mechanism with CO bond breaking.
Also consistent with the above mechanistic hypo- theses are the facts that the k1 term depends on the nature of the metal whereas the k2 term does not so depend; in some instances comparison is not possible. Data relevant to the postulated mechanisms for reac- tions of the type
e) Cr(ox),(NN)-, where NN is en, dipy, phen, or ox, racemization, average AS* = -20.
A carboxylato ligand when bound as a monodentate ligand has two distinct oxygen environments. Thus exchange between the carbonyl carbon and water with- out concomitant hydrolysis is possible. Unless properly accounted for, the isotope data obtained in the hydro- lysis reactions can be misleading. This danger is not so severe, generally, as to vitiate the conclusions given above on the position of bond cleavage.
Although this ambiguity is most often seen with complexes having carboxylato ligands, it is not limited to them. Some other ligands that can show similar electrophilic behavior are acetylacetonate, nitrito, nitro, carbonate, nitrato, phosphato, arsenato, per- rhenato, iodato, etc.
M(NH&0COCF3*+ + OH-+ M(NH3)50H2+ + CF3C02-
are as follows: 14. Second-Order Anations
a) The rate constants at 25” C for the first term (k,) are 1.6 x 10m2, 1.0 X 10e3, and 5 X 104M-’ see-’ for Co, Rh, and Ir, respectively;
b) The rate constants for the second term (kz) are 5.0 X lo-‘, 2.9 x 10-l and 2.7 X 10-‘M-2 se? for the three metals, respectively. The expectations are
The anation process which is the interchange reac- tion involving a solvent molecule as leaving group in the coordination shell and an entering ligand (often an anion, thus anation)
ML5H203+ + X- P ML5X2+ + Hz0
TABLE XII. Activation Parameter? for Base Hydrolysis of Pentaamminerhodium(II1) Carboxylato Complexesb
R
Path I
AH,’ dSl*
Path II
AH** dSz*
CF, 18.0 -13 7.5 -36 cc13 26.4 14 8.4 -39 CHF, 30.1 22 10.5 -32 CH,F 31.9 26 19.1 -17 H 33.2 28 25.6 2 CHs 31.9 22
a The average precision of dH* and AS* values are &OS kcal/mole and +2 cal mol-’ deg’ respectively. b Data of reference 35.
is the reverse of aquation. Since there is no reason to believe that water in the coordination sphere is essen- tially different from other ligands, it seems reasonable to assume that microscopic reversibility holds and that a dissociative interchange mechanism is probable for anation of aquocobali(I11) complexes. Whatever the cause may be, the data given in Data Table VIII are not very convincing as to this point. There is con- siderable variability in the numbers for the same reaction from different research groups, In part, this may be due to the nature of the anation process which is postulated to be a two-step sequence
ML~H~~~+ + x- P (ML~H~~~+ .x-> (fast) {ML5H203+. X-}+MLsX*+ + Hz0 (rate)
with the first step being a rapid ion-pair formation and the second step being the slow interchange. If there
DA
TA
TAB
LE
VII
I. A
natio
n (I
nter
chan
ge);
2nd-
Ord
er
Rat
e C
onst
ants
, z?
Com
poun
d R
epla
cing
p(
M)
PH
Ioni
c Li
gand
M
ediu
m
V(H
zO),“
+ SC
N-
1.0
SCN
- 1.
0 N
CS-
0.
15
dipy
-
SSA
_
NC
S-
O(e
xt)
H,P
Oz
1.0
NH
z _
CO
NH
2
-OC
OC
H,
0.1
Ok
0.1
oxH
2 2.
0 m
a?
0.1
mal
K
1.0
citra
te
0.1
o -p
htha
late
0.
1 cl
- l(7
)
- _ - - _ _ 0.74
_ 4.
85
KN
03
4.85
K
NO
a C
O.7
(N
a,H
)ClO
., 4.
85
KN
Oa
_ _
4.85
K
NO
, 4.
85
KN
03
- _
trnns
-C
r(H
z0)4
C1(
OH
2)Zt
cl
- l(7
)
trans
-Cr(
en)z
Cl(O
H#+
cl-
0.52
C
T 0.
106
cl-
1.71
N
CS-
0.
106
NC
S-
1.71
N
CS-
_
Cl-
10.9
Cl-
10.2
- <3
1.3
1.3
1.3
1.2
2 - -
cis-
Cr(
en),(
DM
SOX
3+
cl-
o-O
.031
-
cis
-Cr(
en),(
DM
S0)2
3+
Bf
o-o.
45
-
cis
-Cro
x2 (
HzO
),-
oxH
- 0.
5 2.
7
k dH
* dS
* C
omm
ents
Ta
ble
Ref
. N
o.
(Na,
H)C
lO,
(Na,
H)C
lO.,
DM
SO
DM
SO
DM
SO
(Na,
H)C
IOJ
none
- NaC
104
Na(
ClO
+Cl)
Na(
ClO
+Cl)
Na(
ClO
+Cl)
Na(
NC
S,B
r)
(Na,
H)(
ClO
,,NC
S)
HC
I
HC
l
DM
SO
DM
SO
(n-B
u)A
NB
r (N
aH)
(ClO
.. %
)
1.0
X lo
+*
(23”
C
) 1.
1 x
lo+*
2.
1 X
1o+
2 1.
1 x
10-l
2.1
X 1
0-l
1.1
x lo
-5
3.0
x 10
-s
6.2
X l
o-’
_ - 4.7
X lo
+
1.0
X 1
oF
_ - 9.8
X 1
o-’
9.8
X
lo-’
1.6X
lO
-6
3.5
X 1
0-6
1.4
X l
o+
2.4
X lo
-’
1.2
X l
o-5
r13x
X1;
~ (3
5°C
) 1.
7 x
1oF
(35O
C)
_
_ -
ST
1 28
6
7.6
-23.
8 _
-
11.7
-2
5 _
-
25.4
4.
0 20
.3
-11.
2 (2
1.4)
(-
15.0
)
S S
F
1
SS
F
202
SW
20
2
SW
20
2 S
17
S
21
1 S
28
9
21.0
23
.2
29.0
22
.4
24.4
22
.2
22.4
_
- -, 14
.1
_ - 0.
1 - _ _ - -
4.5
7 2
3 -9
- 5.
9 - _
1.9
18
_
24.0
26
.6
25.6
24
.2
21.2
23
.4
-
S; k
obt
aine
d by
usin
g ra
te
cons
ts.
atp
= 1
and
eq.
ratio
at
p =
7 S;
k o
btai
ned
by u
sing
rate
co
nsts
. at
p =
1 an
d eq
. ra
tio
atp
= 7
S S S S S S s
290
290
291
290
292
290
290 27
_ 27
43
34
34
34
34
287
288
_ S
288
(9.6
X
lo-
‘)
19.4
(5
.3
X 1
0-6)
30
_ 21
.7
S 36
7 S
366
S;d
H*
refe
rs
to t
he
varia
- tio
n w
ith
tem
p of
the
ob
serv
: k
mea
sure
d w
hen
[oxH
-] =
O.lM
293
cis
-Cro
xZ(H
Z0)
2-
ox=
- 0.
5 6.
0 (N
aH)
- 21
.7
_
cis
-Co(
en)&
l(D
MS
O)‘+
C
l-
cis
-Co(
en)z
Br(
DM
F)2
+
cis-
Co(
en),
Br(
DM
A)”
Cl-
N
CS
- O
XH
- so
4*-
HN
3 C
l-
NC
S-
CH
,CO
OH
HN
a H
zSal
H
Sal
- N
CS
- cl
-
cl-
N3-
N
CS
HzP
Od-
Cl-
NH
3 C
l-
ct
Cl-
cl-
Bi
Br-
(C10
4, 3)
1.0
+7
NaC
104
0.40
0.
7-l
.5
(Na,
H)C
104
0.03
-0.4
5 0.
50
NaC
104
0.5
0.7-
1.3
1.0
1.0
0.40
0.
50
1.0
1.0
1.0
1.0
1.0
0 o-1.
2 o-
1.5
0.5-
l .5
0 0.
2-2
0.2-
2 1.
0-1.
7 3.
0
c (Na,
H)C
104
Na2
S04
H
C10
4 (N
a,H
)ClO
., (N
a,H
)C10
4 (N
a,H
)ClO
., H
C10
4 K
NO
a K
NO
S
(Na,
H)(
CIO
,,NC
S)
Na(
ClO
,,Cl)
0.1
2.0
K(C
lO&
l)
0.5
4.0-
4.9
Na(
ClO
a,N
a)
1.0
5.0
Na(
CIO
+N
CS
)
_ -
1.0
- W
,+ %
) C
l
1.0
0.00
1
[CT
] =
4.
1 x
10-3
M
[Cl-
] =
3.
8x
lo-‘M
[C
T]
=
4.0
x 10
-3M
[c
l-]
=
9.15
x
10-2
M
[CT
] =
- N
fLN
O3
- H
N03
- D
MA
- D
MA
- T
MS
- T
MS
- D
MF
7.
1 x
1c3
M
[cl-
] =
- D
MF
5.
3 x
lo-‘M
_
- D
MF
-
- D
MA
9.4
16.6
2
1.3x
1o
+2
13.0
-5
1.
4 x
1O+
3 18
16
6.
4 X
1O
+3
18.0
19
.4
4.0x
lo
3 -
1.1
x lo
4 13
.1
1.0
x 10
4 10
.0
2.8
x lo
3 11
.1
6.8X
1o
+3
- 5.
5 x
1o+
3 12
1.
4x
lo+
4 11
2.
0x
10-Z
-
6.5~
10~
-
(45
o C
) 2.
8 x
10d
24.1
1.
7 x
10-6
26
.9
6.9x
l@
-
(45
a C
) 2.
2x
lo+
-
-
3.9
- 6.
7 5.
4 - -2
-3
_ - -
3.2
5.2
_
7.3
x lo
-’ 14
.7
1.4x
10-’
12
8.5
x lo
-”
34.2
- -37.
7
-49.
3 28.4
(1
4.6)
-
- 25
.9
- 26
.9
- 25
.9
- 28
.4
- 26
.9
- 26
.9
_ 33
.4
- 33
.4
S; d
H*
refe
rs’t
o th
e va
ria-
29
3 b
tion
wit
h t
emp.
of
the
obs.
$’
k m
easu
red
wh
en [
ox%
] =
z.
O
.lM
a¶
SF
M
299
d ii‘
SF
M
76
R
S
298
3
S
296
3 S
F
c S’
S S
F
300
SF
M
299
B
f S
FM
29
9 b
SW
35
1 i;
S SF
300
5 SSF
301
S
2 SF
301
F
S
322
8 s
303
S;
(2T
, 10
” ra
nge
) 88
S
30
4 S
30
3
S
81
T
103
T
103
T
113
S
306
S
306
S
306
S
306
S
306
S
306
S
270
S;
Pro
duct
s ar
e ci
s an
d tr
am
270
%
DA
TA
TAB
LE
VII
I. (C
ont.)
Com
poun
d R
epla
cing
Li
gand
/O
f)
PH
Ioni
c M
ediu
m
cis-
Co(
en),B
r(D
MA
)*+
Br-
_ tra
ns-C
o(D
H)J
(OH
Z)
Bi
1.0
trans
-Co(
DH
),I(O
H2)
H
SOS-
1.
0 rr
uns-
Co(
DH
)2N
02(0
Hz)
B
r- 1.
0 tra
ns-C
o(D
H)2
NO
z(O
Hz)
N
CS-
1.
0 rr
ans-
C0(
DH
)~N
0~(0
H~)
N
3-
1.0
truns
-Co(
DH
)zN
Oz(
OH
,) H
SO3-
1.
0 C
o(D
H)z
(CH
,)(O
Hz)
B
Y
-
C~(
DH
)Z(C
H~)
(OH
X)
NC
S-
-
_ 2.5-
2.9
2.7-
3.1
3.04
.7
3.74
.0
5.1-
5.9
4.1-
4.5
_ -
DM
A
- 18
.4
KN
03
3.0
x lO
A
17.8
K
NO
3 3.
4 x
1o-3
14
.4
KN
OB
1.
6x
lo4
22.5
K
N03
5.
8 x
lo4
19.1
K
N03
5.
7x
104
16.2
K
N03
8.
5 x
1O-3
15
.0
RY
6.
8 x
lo-’
20
.5
NaN
CS
1.5
17.5
Ru(
NH
~)~O
H~~
+ C
l- 0.
26
1.0
(Na,
H)C
I
Ru(
NH
&O
Hz3
+ B
r- 0.
26
1.0
(Na,
H)B
r
Ru(
NH
&O
H2a
+ I-
0.
26
1.0
NaI
cis-
Ru(
en),(
OH
z)23
+ ci
s-R
u(en
)z(O
H2)
23+
cis
-Ru(
en)z
CIO
HzZ
+ ci
s-R
u(en
),BrO
H2*
’ R
h(N
H&
0Hz3
+ R
h(N
Ha)
sOH
z3+
CI-
0.
26
Br-
0.26
C
l- 0.
10
Bi
0.50
C
l- 0.
0125
cl
- 0.
20
0.6
0.6
1.0
0.3
2.6
larg
e ex
cess
la
rge
exce
ss
larg
e ex
cess
la
rge
exce
ss
(Na,
H)C
I (N
a,H
)Br
HC
l H
Br
(Na,
H)(
Cl,C
lO,)
Na(
CI,C
lO.,)
Bf
0.20
0.20
0.20
_ 0.20
0.
20
0.20
0.
20
0.50
0.
20
0.50
4.0
4.0
3.7
Na(
Br,C
lOd)
4.
6 x l
o+
25.3
1.
9
I-
Na(
I,C10
4)
4.3
x lo
4 24
.4
- 1.
4
NC
S-
Na(
NC
SC10
4)
5.0
x lo
+ 23
.8
- 3.
0
cl-
cl-
Bi cl-
Bi
cl-
Bi I-
- 4 4 4 4 4 4 4 <o
<o
CO
_ Na(
CI,C
lO.,)
N
a(B
r,C10
4)
Na(
CI,C
l04)
N
a(B
r,Cl0
4)
Na(
CI,C
104)
N
a(B
r,ClO
a)
Na(
I,C10
4)
trans
-RhC
L,(O
H&
- R
hC15
(0H
$ Ir
Ch(
OH
&
CI-
C
l- CT
H(C
I,C10
4)
3.5
x 10
-4
21.3
H
(CI,C
104)
2.
2 x
lOA
16
.5
(Na,
H)C
lOd
5 x
lo-’
28
.2
k dH
* dS
* C
omm
ents
Ta
ble
Ref
. N
o.
2.1
x lo
@
(54.
7”C
) 1.
3 x
10”
(54.
7”C
) 7.
4 x
104
(54.
7”C
) 2.
5 x 1
O-3
1.
8 x
10”
4.3
x lo
4 1.
9x
lOA
1.
5 x
1o-5
6.
8 x
lOA
_ - - 18.8
-
7.3
S 31
0 19
.6
- 5.
3 S
310
23.4
4.
6 S;
klp
t an
ddH
* &
r 31
0 21
.4
- 3.
7 S
310
27.6
12
.0
S 18
5 25
.5
3.2
S 18
7
_ 25
.2
2.4
x lo
-’
25.3
2.
3 x l
o-’
24.4
3.
5 x
l@
22.0
2.
6 x
lo4
22.3
6.
1 x
lo-’
19
.5
6.0 x l
o--’
18
.6
5.1
x lo
-2
18.0
- _14
-21
--/T
y?
- -1
9 -I
7 - 19(9
.5)
:19o
, _ - - -
5.2
2.0
0.5
0.4
0.6
- 1.
4 0.
3 (-
4.1)
-2
.9
-19.
9 7.3
S; 1
00%
tra
ns
prod
. 27
0 S
307
S 30
7 S
307
S 30
7 S
307
S 30
7 SS
F 29
4 SS
F 29
4
S 31
0
S 31
0
S 31
0
S S S _ S S S S S S S S S S
187
187
4 P
187
$ 31
2 Q
31
3 ?
313
313
313
; w
313
313
B
313
%
:
193
194
$ a 19
8 8.
L&and Replacements in Octahedral Complexes 95
is so little ion-pairing that the reaction is truly second- order under the conditions chosen, the values obtained by different groups should agree. If, however, the changeover from second-order to first-order has start- ed, agreement on “second-order rate constants” could be poor.
In spite of this variability in results, there are some interesting mechanistic clues in Data Table VIII that may be useful in the general context of this review:
a) The two values of dS* for anation of V(II1) complexes are very negative as is the value for aqua- tion of V(H20)5NCS ” in Data Table I. This is felt to be good evidence for a fair amount of associative behavior in the mechanism of replacement in V(II1) complexes.
b) The two dS* values for anation of CO(NH~)~ OS202+ are so far from other Co(II1) data that some doubt as to the nature of the process investigated is justified.
c) The values of d S * for anation of truns-Co(DH)2 X(H20) from reference 307 are more negative than for most cobalt complexes. Since a significant truns-
effect may obtain in these complexes, one must con- sider the possibility that the trans-effect in these com- plexes is a consequence of a mechanistic shift towards a greater degree of associative character.
15. First-Order Anations
First-order anations can arise from two different types of reaction. If the complex is cationic and the entering ligand is an anion, the two-step sequence
ML,(H,~)~+ + x- P {ML,(H~O).X}*+
{ML5(H20)~X}Z++ML~X2+ + Hz0
wherein the wavy brackets denote an ion-pair, is often postulated.
When the amount of entering anion ligand is suffi- ciently high so that all of the reactant complex is in the form of the ion-pair {ML5H20.X}*+, the kinetics are changed over to first-order in ion-pair and the rate becomes independent of anion concentration (but not necessarily of anion nature). For example, the ion pair {CO(NH~)~(H,O). Cl}“+ has been postulated36 in the reaction for formation of the chloropentaammine com- plex. This mechanism is much favored by inorganic chemists at the present time.
Another path leading to first-order rate constants can obtain in the absence of ion-pairing. This mecha- nism also has two steps, as follows:
ML5(H,0)” + ML5” + Hz0 1
ML5” + X-9 ML5X”-’
96
Here a five coordinate mtermedlate 1s formed Usmg the steady-state approxlmatlon It can be shown that when k,[X-] % kl[HzO] the rate law 1s
v = kl[ML5(HzO)“]
This first-order anatlon ~111 obtam when X- 1s a much stronger nucleophle, m this case, the observed rate 1s independent of both nature and concentration of nucleophlle (provided of course that it 1s strong) 23d This type of mechamsm seems appropriate for anation of Co(CN)S(H20)”
The results for first-order anatlons are given m Data Table IX In view of the Importance of this type of kinetics to our understandmg of the hgand replace- ment processes m octahedral systems the amount of data IS dlsappomtmg some high quahty data are needed
16 Actwatlon Volumes
The eleven pieces of data m Data Table X are useful for they give conflrmatlon to some of the conclusions dlscussed above The actlvatlon volume for water ex change of Rh(NH3)5(H,0)3+ 1s more negative than for CO(NH~)~(H*O)~+ this 1s reasonable on the basis that replacements m rhodmm(II1) complexes have a greater degree of assoclatlve character than do those of cobalt(III) For Cr(NH3)5(H20)3+ a slmllar behdvlor 1s expected Also the value of dV* for exchange between Cr(H,0),3’ and Hz0 1s sufflclently negative to mdlcate associative character
It IS interesting to note and it IS not unexpected to see that as dV* decreases (becomes more negdtlve) the correspondmg value of d S’ also decreases
The other mslght m these data IS to be found m the values of dV’ for aquatlons of complexes of the type CO(NH~)~X”+ As the charge on the ledvmg hgand becomes more negative charge separation m the transltlon state becomes a more Important factor Ions tend to shrmk the solvent around themselves and this process 1s known as electrostrlctlon In gomg from ground state to a transltlon state with charge separa tlon the contrlbutlon of electrostrlctlon to the value of dV* would be negative (smaller net volume) No charge separation obtains when X 1s Hz0 There 1s some charge separation when X 1s a mononegatlve Ion (CT Bi and N03-) Charge separation 1s very lm- portant when X 1s sulfate ion The values of d V’ for the three cases are +l 2 -8 1 (average of the three values) and -16 9 cm3 mar’ The order IS as predlct- ed on the basis of electrostrlctlon Further evidence that electrostrlctlon 1s a correct (although mcomplete) explanation comes from the observatlon37 that dV* IS vntudlly ldentlcal of dV for the overall reaction This also 1s consistent with bond breakmg bemg very
J 0 Edwards F Monacellr and G Ortaggi
L&and Replacements in Octahedral Complexes
DATA TABLE X. Activation Volumes.
97
Complex AV+ (cm3/mol)
Reaction Table Ref. No
Cr(H20)b3+ - 9.3 Exchange Cr(H20)5(ONOz)‘+ -12.7 Aquation Cr(NHa)s(OH? - 5.8 Exchange Co(NHz)s(OH#+ 1.2 Exchange Co(NH&CI’+ - 9.7 Aquationa Co(NH3)5Br2+ - 8.6 Aquation” CO(NH~)~(ONOZ)*+ - 5.9 Aquation” Co(NH&OSOs)+ -16.9 Aquationa CoNH3)5BrZf 8.5 Base hydrolysis Rh(NH&(OH#+ - 4.1 Exchange trans-Cr(ox)Z(H20)2- -16 Trans-+cis isomerizatior?
ad V” is virtually coincident with the change of volume of the overall reaction. b d V* becomes -9.8 cm3/mol in the presence of Ca(N0 3 ) 2 and -5.4 in the presence of HClOd.
317 311 318
80 319 319 319 319 226 318 365
important, since the closeness in size of dV* and AV suggests that the leaving group is nearly as free in the transition state as in the final state. The positive (albeit small) value of the activation volume for water exchange is in agreement with such an interpretation.
17. Summary Conclusions
The present compilation is, to the best of our know- ledge, the most complete set of data dealing with rates and mechanisms of octahedral complexes having the central metal in oxidation state three. We hope that the numbers collected and calculated will be use- ful to inorganic chemists. Also it is our opinion that good activation parameter data (specifically, d H* , AS’ and AV* ) can be helpful in elucidating the mechanisms of ligand replacement in complexes and that such data should be obtained carefully (whenever possible) in reaction mechanisms studies.
18. Acknowledgements
We are much indebted to Professor G. Illuminati of the University of Rome for helpful discussions and for providing us a most favorable ambient. Financial support was provided by the Centro di Studio dei Meccanismi di Reazione de1 Consiglio Nazionale delle Ricerche of Italy and the United States Air Force Office of Scientific Research (Grant d/71-1961A). One of us (J.O.E.) was generously granted a Fellow- ship by the John Simon Guggenheim Memorial Foun- dation. Also we thank Mrs. Bert Hanson for her skill, accuracy and thoughtfulness in assisting with the manuscript preparation.
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129
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132 133 134
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143
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153
154 R.G. Linck,Inorg. Chem., 8, 1016 (1969).
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155 V.D. Panasyuk and S.A. Shevchenko, Vim. Kiivs’k. Univ. Ser. Astron. Fis. ta Khim., 2, 99(1962); CA 62:13898c.
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157 M.J. Frank and D.H. Huchital, Znorg. Chem., 11, 776 (1972).
158 V.D. Panasyuk and V. D. Arkharov, Ukr. Khim. Zh., 31, 338 (1965) CA 63:12373g.
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196 197
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284 285
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293 294
L&and Replacements in Octahedral Complexes
295
296
297
298
299
300 301
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303
304
305
306
307
308
309
310
311
312 313 314
31.5
316 317
318
319
320
321
322
323
324
325
326
327
328
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330
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341 __
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104 J. 0. Edwards, F. Monacelli and G. Ortaggi
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