Upload
eric-cannon
View
223
Download
0
Embed Size (px)
Citation preview
8/11/2019 Summary Inorganic Chemistry _ v0.05
1/18
]][)([
]][)([
62
2521
LOHM
OHLOHMK
z+
=
= nK6
= )log()log( 6 nK
nz
m
z
n
n
LOHMML
]][)([][
2
+
+
=
Summary inorganic chemistry part 1
Paragraph 6.11: Coordination complexes. In a Coordination complex a central atom or
ion is coordinated by one or more molecules or ions (ligands) which act as
Lewis bases (donates electrons), forming coordinate bonds with the centralatom or ion which acts as a Lewis acid (accepts electrons). toms in the
ligands that are directly bonded are called donor atoms. line is used to
denote the interaction between an anionic (negati!e ion) ligand and the
acceptor, an arrow is used to show the donation of an electron pair from a
neutral ligand to an acceptor. "he resulting species from a coordinate bond is
called an adduct. Can be indicated by a dot, e.g.# $%&'"$.
eutral complexes are usually sparingly soluble in water, but readily soluble in
organic sol!ents. "he p$ also has an e*ect, $+can compete for the ligand, and $ -can act
as ligand.
Paragraph 6.12: Stability constants. etal ions are often
hydrated, /($0)123+ is often written as 3+. 45uilibrium
constants (normally written without /$02 because that6s the
unity) for each displacement step (e.g. 78depicted on the right
here) can be ta9en together by multiplying them (also see
right), resulting in the o!erall stability constant n. :sually
stability constant 7ndecreases with increasing n (more ligands).
$ighly charged ions more negati!e ;hydcantly
negati!e) ? ;@=substantially negati!e.
umber of donor atoms through which ligand
coordinates is called denticity of ligand (mono-, didentate etc).
Aolydentates ? chelate ring (chelate from crab6s claw) with bite
angle B--. 1 membered ring is stabili3ed D-bonding.
8/11/2019 Summary Inorganic Chemistry _ v0.05
2/18
Paragraph 19.2: Ground state e- congurations. etals are elements that readily lose
electrons to form cations. F-bloc9 metals shown in image below. transition element (G d-
bloc9 metal) is an atom that has incomplete d-subshell or forms cations with incomplete
subshells. 4ach group of d-bloc9 metals consists of three members and is called a triad, >rst
and second row metals denoted by hea!ier. irst, second and third row correspond
respecti!ely >lling %d, Hd, and Ed orbitals, from which there are howe!er minor de!iations.
0+and %+ions of >rst row metals all ha!e /r2%dn.
Paragraph 19.!: Physical properties. etallic radii show little !ariation across a gi!en
row of d-bloc9, the >rst row metal is has smallest radii, the second and third are similar. "his
last fact is due to the lanthanoid (La (E) J Lu (8))contraction# the steady decrease in si3e
along the lanthanoid elements. etals of d-bloc9 hard, ductile, malleable, less !olatile then s-
bloc9. ll %d metals ha!e !alues of I48and I40larger than those of calcium and all (except
3inc) ha!e ha!e higher !alues of Ka$=, which ma9e them less reacti!e than calcium.
8/11/2019 Summary Inorganic Chemistry _ v0.05
3/18
(..) (paramagnetism). Intercon!ersion between oxidation states characteristic of d-
bloc9 metals. pparent oxidation state from molecular or empirical formula may be
misleading, e.g. La%+(I-)0(e-), sometimes metal-metal bonds or ambiguous oxidation states,
e.g. /"i(bpy)%2n-(n =, 8, 0).
Paragraph 19.6: &lectroneutrality. Aauling6s electroneutrality principle estimates charge
distribution by assuming charge on single atom only -8 to +8. O
Co
NH3+
NH3+
NH3+
NH3+
+H3N
+H3N
3-
Co
H3N
NH3
NH3
NH3
H3N
H3N
3+
Co
NH3+
NH3+
NH3+
NH3+
NH3+
NH3+
3+
Co
NH31/2+
NH31/2+
NH31/2+
NH31/2+
H3N
H3N
1/2+
1/2+
conventional 100% covalent 100% ionic inbetween
Paragraph 19.': Coordination numbers.Coordination numbers and geometries are often
distorted from regular geometries, because e.g. steric e*ects. If there6s a small energy
di*erence between geometries, Puxional beha!iour in solution may be obser!ed.
In the 7epert model the metal lies at the centre of a sphere o!er which the ligands are
free to mo!e. "he ligands are considered to repel each other li9e Qguration. Common arrangement in the table on the right, not all are predicted by 7epert
because electronic factors or the inherent constraints of ligands. "ripodal ligands are ligands
containing three arms, each with a donor atom, originating from central atom or group which
also may be donor.
Coordination number 2. :ncommon, restricted only a few metal-ions (d8=). Coorindation
number 3. lso uncommon, also in!ol!ing d8=.
8/11/2019 Summary Inorganic Chemistry _ v0.05
4/18
is called the Uahn-"eller e*ect. lso a small group of d=and d8trigonal prismatic or distorted
trigonal prismatic en!ironment. Coordination number 7.4arly second V third row (and also
lanthanoids and actinoids), rcationmust be relati!ely large. In reality much distortion from
these structures. Coordination numbers 8, 9 and 10. (..)
Paragraph 19.(: )somerism. (..) (Read blue boxes).
Ligand
s
Geometr !bridi"atio
n0 linear sp
% trigonal planar sp0
H tetrahedralW sp%
H s5uare planar sp0d
E trigonal bipyramidal sp%d
E s5uare based pyramidal sp%d
1 octahedral sp%d0
pentagonal bipyramidal sp%d%
S dodecahedral sp%dH
S s5uare antiprismatic sp%dH
S hexagonal bipyrimidal X
T tricapped trigonal
prismatic
sp%dE
8/11/2019 Summary Inorganic Chemistry _ v0.05
5/18
Paragraph 2*.2: $alence bond
theory. Qalence bond theory
(hybridi3ation and o!erlap)#
hybridi3ation schemes can be used to
describe bonding d-bloc9 metals. &ut
!alence bond theory is !ery unrealistic
when trying to describe metal
complexes. guration, where electrons are put unpaired in %d shell to achie!e diamagnetism (or high
spin) and Hd shell thus has to be used for hybridi3ation.
Paragraph 2*.!: crystal eld theory.
Ligands are considered points charges and
there are no co!alent metal-ligand interactions.
4lectrostatic >eld crystal >eld. g. 0=.0,
if spherical approach ligands, all %d orbitals
would be raised. &ut octahedral approach# d30
and dx0-y0raised more than dy3, dyxand d3x(the
closer the ligand, the greater the raise in
energy, - Y - repulsion). "he separation
energy is Koct, because the total energy remains the same, and two and three orbitals are at
the same energy le!el, energy is splitted =.1 and =.H Koct. agnitude of Koctis determined by
the strength of the crystal field# Koct(strong field) Z Koct(wea9 >eld). Nith absporption
spectrum ion, e-promotion from t0g to eg(the resulting orbitals from splitting the d-orbital)
can be seen and Koctcan thus be estimated. Koctdetermined by identity and oxidation metal
and nature of ligands. Koctdepends on ligands as follows#
"
L
L
L
L
L
L
n+#
$
%
8/11/2019 Summary Inorganic Chemistry _ v0.05
6/18
/wea9 field# Koct[2 I\] &r\] lled completely >rst, and in high spin the aufbau principle goes for
all orbitals. "he electrons will >ll the orbitals creating the lowest C
8/11/2019 Summary Inorganic Chemistry _ v0.05
7/18
complex will thus be low spin. "he other way around# if Koct] A (wea9 crystal >eld), it is more
energy ecient to put the electrons in the higher orbital (eg) >rst, if these are empty.
-a$n/e**er distortions.Uahn-"eller distortions originate
if electron density is not e5ually distributed. "he
metal-ligand bond lengths are stretched if nearby
orbitals are >lled and !ice !ersa (see image), leading
to a distortion. "his is often the case in octahedral dH
and dTcomplexes.
/$e -a$n/e**er t$eorem states t$at an non*inear mo*eu*ar sstem in a degenerate
e*etroni state #i** be unstab*e and #i** undergo distortion to 'orm a sstem o' *o#er
smmetr and *o#er energ, t$ereb remoing t$e degenera.
/etra$edra* rsta* +e*d. dxy, dy3, dx3orbitals nearer to ligands than
d30 and dx0-y0. Ktet HT'Koct, because Ktet is smaller, tetrahedral
complexes are high spin. lso di*erent colours. In eHH- Uahn-
"eller distortions lead to di*erent bond angles.
uare *anar rsta* +e*d.Can be deri!ed by remo!ing two trans ligands from an
octahedral con>guration. 4.g. from 3-axis, d30greatly stabili3ed, dy3and dx3(also
point partially in 3-direction) also stabili3ed, dx0-y0 is massi!ely destabili3ed, whereas dxy is
moderately destabili3ed. /iClH20- is tetrahedral, while /Ad(II)BH23- and /At(II)BH23- are both
s5uare planar, because Ad and At (0ndand %rdrow) cause larger crystal >elds.
t$er rsta* +e*ds.
8/11/2019 Summary Inorganic Chemistry _ v0.05
8/18
+ctahedral Pentagonal bipyramidal S,uare antiprismatic
S,uare planar S,uare pyramidal etrahedral
rigonal bipyramidal
Paragraph 2*.": olecular orbital theory. olecular orbital theory o*ers alternati!e for
the crystal >eld theory. irst ta9e a loo9 at %.0 and pp 8=T.
Paragraph !.2: Symmetry operations / elements. symmetry operation is an
operation which lea!es it in a con>guration that is indistinguishable from its original
con>guration. "he operation is carried out with respect to symmetry elements, i.e. points,
lines or planes. "he symmetry operation around an n-fold axis is noted by Cn, n-fold meaning
that a (%1=n) rotation leads to the same con>guration. If a molecule possesses more than
one axis, the axis with the highest n-!alue is called the principal axis.
8/11/2019 Summary Inorganic Chemistry _ v0.05
9/18
!(!ertical). !refers to the plane bisecting the ($--$) bond and !6 refers to the plane in
which the molecule lies. d(dihedral) label is gi!en if the plane bisects an angle between
two Cnaxes.
"he center of in!ersion is the point from which you can draw an in>nite number of
straight lines such that each line passes through (a) pair(s) of similar points, one on each
side of the centre of symmetry and at e5ual distance from it.
rotation followed by a rePection through a plane perpendicular to that axes, which
is called the improper rotation axis, resulting in the same con>guration, is designated with
8/11/2019 Summary Inorganic Chemistry _ v0.05
10/18
mb
o*
eration *ement am*e
Cn Rotation n-fold axis
(%1=n)
RePection Alane
i Centre
8/11/2019 Summary Inorganic Chemistry _ v0.05
11/18
Paragraph 2*.": olecular orbital theory continued3. theory does consider
co!alent interactions in complexes.
t$eor (based on $ater 4 120: ;6)
theory compares symmetries to establish a molecular orbital diagram. or example, a
>rst row metal has %d, Hs and Hp !alence shells. "hose can be di!ided in di*erent
symmetries.
Hs a8gsymmetryHp t8usymmetry%dx0-y0, %d3 egsymmetry%dxy, %dy3, %dx3 t0gsymmetry
It is 9nown that only p orbitals of the ligands interact with the metal.
ore precise, only the p3orbitals (if each ligand is gi!en its own axis
set). urthermore, from an examination of how many of these p orbitals
are the same after hsymmetry operations it can be concluded that
the L@ is a sum of 8g, "8uand 4gsymmetries. 1 new wa!efunctions
can thus be deri!ed by mixing the p orbitals.
"o construct the diagram, orbitals of same symmetry are
mixed. rbitals with another symmetry become non-bondingorbitals. Fisplayed to the left an image of bonding in
8/11/2019 Summary Inorganic Chemistry _ v0.05
12/18
"here is greater o!erlap between the metal s and p orbitals and the ligand p orbitals than
between the metal %d and the ligand p, which leads to more stabili3ation. If there is no Dbonding, the energy le!els between t0gand eg` correspond with Koct. b!iously, if the eg, t8u
and a8g orbitals are >lled (which can be done by the electrons supplied by the ligands), the
remaining electrons (from the metal) are di!ided depending on wea9 or strong >eld, ust as
in the crystal >eld theory.
Com*ees #it$ < bonding a*so.
8/11/2019 Summary Inorganic Chemistry _ v0.05
13/18
ll the orbitals below the green orbitals (see picture).
or better, but still 5ualitati!e pictures, see p. E1S boo9. $owe!er, conclusions can be
drawn#
- Koctdecreases in going from -only complex to - and D-complex (compare abo!e
donor picture to picture on pre!ious pageW and bare in mind that eg` stays e5ual).
o or a complex with D-donor ligands, increased D-donation (X) stabili3es t0gle!el
and destabili3es t0g`, thus decreasing Koct.
- Koct!alues are relati!ely large for D-acceptor ligands, and those complexes are thus
li9ely to be low spin.
o or a complex with D-acceptor ligands, increased D-acceptance stabili3es t0g,
increasing Koct.
urthermore, since >lling antibonding orbitals is detrimental for complex-formation,
octahedral complexes with D-accepting ligands will not be fa!oured by dnZ1. n obser!ation
8/11/2019 Summary Inorganic Chemistry _ v0.05
14/18
can be made that d-bloc9 metals tend to obey the e*ecti!e atomic number rule or the 8S-
electron rule. lling the !alance shell. "he 8S-eletron rule is useless for higher
oxidation state metals, can be rationali3ed by smaller energy seperations. ther complexes
than octahedral fall out of the scope of this discussion (see p. E=).
(..W some exceptions for ).
Paragraph 2*.%: 4igand eld theory. Non6t go in to mathematics of ligand >eld theory,
howe!er, ligand >eld theory is an extension to crystal >eld theory which is freely
parameteri3ed (as opposed to locali3ed >eld from point charge). It is also con>ned to d
orbitals. part from Koctit also uses Racah parameters which are obtained from electronic
spectroscopic data.
Paragraph 2*.6: &lectronic spectra.bsorptions arise from transition between electronic
energy le!els#
- "ransitions between metal-centred orbitals possessing d-character (jd-d6 transitions).
o Nea9er.
o Can be mas9ed due C" transition.
- "ransitions between metal- and ligand-centred s which transfer charge from metal
to ligand or !ice !ersa.
o ore intense.
o LC"# metal-to-ligand charge transfer
o LC"# ligand-to-metal charge transfer
k is wa!elength, is propagation speed en c is the speed of light, is the
wa!enumber.
bsorptions are relati!ely fast in comparison to molecular !ibrations and rotations (with
which the energy le!els change), hence, the obser!ed absorption fre5uencies !ary. "here isan absorption maximum kmax (nm), with corresponding max (absorbance), kmax is used to
describe the particular band. "he molar extinction coefficient (a9a molar absorpti!ity) max#
Nhere maxis the molar extinction coecient, maxthe maximum absorption (
kmax), c the concentration, and l the pathlength (in cm) of the spectrometer
cell.
c
==
1
=c
A!a%!a%
8/11/2019 Summary Inorganic Chemistry _ v0.05
15/18
ote (without explanation) that#
- d8,H,1,Tcomplexes consist of one absorption.
- d0,%,,Scopmlexes consist of three absorptions.
- dEcomplexes consist of a series of wea9 but sharp absorptions.
e*etion ru*es.
8/11/2019 Summary Inorganic Chemistry _ v0.05
16/18
4.g. a @ouy balance# sample is hung in balance and magnetic >eld
applied to it, sample mo!es and di*erence in weight can be read
out, from which magnetic susceptibility, m, can be determined.
;erromagnetism, anti'erromagnetism and 'errimagnetism. If metal
centres are separated by diamagnetic species, they are said to be magnetically dilute.
Nhen paramagnetic species are close together (bul9 metal), or separated by species able to
transmit magnetic interactions (as many d-bloc9 oxides, Puorides and chlorides are), the
metal centres can couple (interact). "his may gi!e rise to ferromagnetism or
antiferromagnetism.
In a ferromagnetic material, large domains of dipoles
are aligned in the same direction. In anantiferromagnetic material, neighbouring magnetic
dipoles are aligned oppositely. bo!e the Curie
temperature ("c) the thermal energy is sucient to
o!ercome the alignment. ntiferromagnetism occurs
be*o# the qel temperature ("). errimagnetism
occurs when relati!e !alues of momenta are di*erent.
Nhen a bridging ligand facilitates coupling of
electron spins on adacent metal centres, this
happens by super-exchange. "he two metal centres
(in image on the left and right) interact with two
spin-paired electrons in the same orbital of a ligand. guration in the also has to be spin-paired, the result is an anti-parallel coupling of
the two metal centres.
Paragraph 2*.9: ligand eld stabili5ation energies 4S&3. Lgurations, it shows
remar9able similarities with other thermodynamic energy trends, such as lattice energies
and hydration enthalpies of metals. Fe!iation from the dotted line may thus be ta9en as
measures of thermochemical L
8/11/2019 Summary Inorganic Chemistry _ v0.05
17/18
s can be seen the >gure abo!e, d=,E,8=complexes should
not fa!our octahedral or tetrahedral con>gurations.
$owe!er, other factors should be ta9en into account. 4.g.
the smaller si3e of tetrahedral complexes results in
higher lattice and sal!ation energies, hence, for example
i0+(dS) does not form tetrahedral complexes in a5ueous
solutions, only in melts or non-a5ueous media.
(..W !erhaal o!er spinels).
Paragraph 2*.1*: he )r$ing-7illiams series. In a5ueous solutions, water is replaced by
other ligands, and the position of this e5uilibrium will be related to the di*erence between
the two L
8/11/2019 Summary Inorganic Chemistry _ v0.05
18/18
"his trend can also be explained by dependency on dncon>gurations (and not only on the e*
increment leading to a decrease in radius). $owe!er, this trend also doesn6t explain the
stability of copper. Copper is !ery stabile because a dTcomplex has a Uahn-"eller distortion.
"his also renders the image of a >xed ionic radius useless. ppearantly in this distortions H
stronger bonds compensate for the 0 wea9er (longer) bonds in such a way to ma9e it more
stabile than i(II).
Paragraph 2*.11: oxidation states in a,ueous solutions. 4=!alues (..W nog le3en- na
deel 0).
+o8 nog doen:
- Chelaat e*ect meer uitleg 3ie %S