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This article was downloaded by: [University of Chicago Library]On: 12 November 2014, At: 13:06Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,37-41 Mortimer Street, London W1T 3JH, UK
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SYNTHESIS AND STRUCTURAL INVESTIGATION OF METALCOMPLEXES OF 1-AMIDINO-2-THIOUREASChitta R. Saha a & Nitish K. Roy aa Department of Chemistry , Indian Institute of Technology , Kharagpur, 721302, IndiaPublished online: 13 Dec 2006.
To cite this article: Chitta R. Saha & Nitish K. Roy (1983) SYNTHESIS AND STRUCTURAL INVESTIGATION OF METAL COMPLEXESOF 1-AMIDINO-2-THIOUREAS, Journal of Coordination Chemistry, 12:3, 163-176, DOI: 10.1080/00958978308073845
To link to this article: http://dx.doi.org/10.1080/00958978308073845
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J. Coord. Chem., 1983, Vol. 12, pp. 163-176 0095-8972/83/ 12036163 $lS.SO/O
0.1983 Cordon and Breach Sdenca Publisherr. Inc. Printed In Gat Britain
SYNTHESIS AND STRUCTURAL INVESTIGATION OF METAL COMPLEXES OF 1-AMIDINO-2THIOUREAS
CHITTA R. SAHA and NITISH K. ROY Department of Chemlrtry. Indhn Inxtitute of Technology, Kharaginu 721302, Indh
(Received Jury 6, 1982)
Some new metal complexes of l.amidino-2-thioureast and itr S- and Nrlky l derivatives hvc been isolated and characterized by electronic, vibrational and pnu spectral studios, magnetic and con- ductance measurements and thermal aMIysL. The ligands behave u SN or NN donorn depending mainly on the pH of the medium and the nature of the metal atom. Protonation at the central nitro- gen atom of the chelate ring converts the inner complexes to cationic onel md vice-versa. Electronic and pmr spectral data confirm the presence of strong ring currents in thew chehtettl. Probable structures of the complexes have been ruggerted on the buir of their phyricochemical propertien.
INTRODUCTION
Few investigations on the synthesis and structure of metal complexes of 1-amidino-2- thioureas have been made so far.'" Earlier workers suggested nonplanar chelate ring structures for them?,'" The ligands possess nitrogen and sulphur donors and the relative coordinating abilities of these donor atoms should depend on experimental conditions and the nature of the metal atoms. As SN donors, they stabilize lower oxidation states of metal atoms' and lower and electron density on NO in metal nitros 19.' The structures of metal complexes of similar hands like biguanide and dithiobiuretr-16 suggests similar nelectron delocalized structures for these metal complexes. In the present paper we report the isolation of some new complexes and propose most probable structures on the basis of their physicochemical properties.
EXPERIhfENTAL
Analytical grade reagents and pure distilled solvents were generally used throughout the work. The ligands and the known compounds were prepared according to l i t~rature!"~~~~' Vibrational (in KBr mull), electronic and pmr spectral studies, magnetic and conduc- tance measurements and thermal analysis were carried out using Beckman IR-12, Cary 17D and EM 390 90 MHz spectrophotometers, a Couy balance, a Phillips conductivity bridge and derivatograph, and a Paulik and Erdey instrument, respectively.
Reparation of the Complexes The numbers used in this section refer to corresponding complexes in Table 1,
Synthesis of NN Bonded Complexes
Nickel(II) Complexes Ni(HSEATU),X,; (X = Cl, Br, I). Saturated ammonium halide solution was added
tHATU - I-.midino-2-thioure8, HMNATU unidino-2-thiouru, HSEATU = Scthyl-l-unidino-2-thiourea.
N-methybl-Midin0-2-thiou1~~ HNEATU = N-ehtybl-
1 A 1
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14
c
QI
P
1.
2.
3.
4.
5.
6.
7. a. 9.
10.
11.
Co(
ATU
), 1.
5H,O
12.
(Co(
AT
U),(
%o)
a
13.
Co(
SEA
TU),(
OH
)
- Oran
ee
0- 0- Ros
a rsd
Ros
e red
Row
red
Ros
e re
d
B h
e
Blue
Ora
nge
Ora
nge
0-0
14.0
7 (1
3.98
)
11.6
5 (1
1.55
)
9.60
(9
.73)
12
.80
21.4
9 (2
1.34
) 14
.95
12.3
9 ( 1
2.3 1
)
13.5
9 (1
3.52
) 20
.19
(20.
06)
15.7
9 (1
5.65
) 13
.60
(13.
49)
16.1
1
15.4
1 (1
5.36
)
(1 2.
88)
(14.
88)
(16.
18)
26.7
5
2209
(2
2.01
)
(26.
68)
18.4
0 (1
8.5
8)
24.3
5 (2
4.20
) 37
.52
(3 7.
64)
26.3
9 (2
6.26
) 21
.79
(21.
72)
23.9
7 (2
3.85
) 17
.85
(13.
81)
(17.
69)
13.9
2
35.7
2 (3
5.69
) 30
.69
(30.
72)
29.2
5 (2
9.16
)
22.7
0 (2
2.7 6
) 18
.70
15-7
3
20.5
2 (2
0.65
) 16
.09
(16.
13)
22.4
0 (2
2.50
)
(18.
79)
(15.
87)
18.5
3 (1
8.62
1 20
.32
(20.
44)
15.1
0 ( 1
5.1 6
) 18
.71
(11.
831
16.3
0 (1
6.36
) 13
.10
(13.
16)
(25.
00)
24.8
5
15.3
5 ( 1
5.24
) 12
.70
(1 2.
58)
(10.
61)
13.9
5
21.6
5 (2
1.51
) 15
.21
(15.
00)
12.3
1 (1
2.41
)
(13.
63)
10.2
5 (1
0.11
) 7.
95
10.8
2
(13.
83)
13.8
5
(7.8
9)
21.8
1 (2
1.96
) 17
.62
(1 7.
55)
16.5
2 (1
6.66
)
16.9
9 (1
6.91
) 31
.70
(31.
45)
42.2
5 (4
2.44
)
(20.
74)
20.8
4
16.7
2 (1
6.64
) 31
.21
(31.
03)
(20.
44)
22.4
3 (2
2.41
)
39.5
2 (3
9.45
)
20.6
0
9.81
(9
.73)
250
248
250
250
255
255
255
r F 3 2 X
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Tabl
e 1
an
t.
14.
[Co(
HSE
ATU
),(H
,O),l
C1
,
15.
[Co(
HSE
ATU
), (H
,O),]
Br,
16.
Ni(H
ATU
),C4
1.5H
,O
17.
Ni(H
ATU
),Br,.
H,O
18.
Ni(H
ATU
),(N
O,),
H,O
19.
NY
ATU
),
20.
Ni(H
NM
ATU
),Cl,
21.
Ni(H
NM
ATU
),Br,
22.
Ni(H
NEA
TU),
C1,
23.
Ni(H
NEA
TU),
Br,
24.
Ni(H
NM
ATU
), SO
, 1 SH
,O
25.
Ni(N
MA
TU),
26.
NN
NEA
TU),
27.
Cu(
HN
MA
TU),
F,
28.
Cu(
HN
MA
TU),S
O,
l.SH
,O
R ed
dis h
-yel
lo w
Red
dish
-yel
low
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Blu
ish
B lui
sh-p
ink
11.8
0 (1
1.94
)
9.30
(9
.39)
14.8
7 ( 1
4.94
) 12
.52
(12.
41)
13.5
2 (1
3.44
)
20.1
7 ( 2
0 .O 5
) 14
.98
(14.
90)
12.0
5 (1
2.16
)
13.7
9 (1
3.91
)
11.5
6 (1
1.49
)
13.5
1 (1
3.44
)
18.3
5 (1
8.30
) 16
.87
(16.
83)
17.3
9 (1
7.46
) 14
.11
(14.
17)
22.9
0 (2
2.69
)
17.9
9 (1
7.86
)
28.4
0 (2
8.52
) 23
.65
(23.
69)
25.6
7 (2
5.64
)
38.4
0 (3
8.26
)
28.5
6 (2
8.44
)
23.4
0 (2
3.20
)
26.5
9 (2
6.55
)
21.8
2 (2
1.93
)
25.7
0 (2
5.64
)
34.8
1 (3
4.92
) 31
.19
(31.
12)
30.7
0 (3
0.81
)
24.8
8 (2
4.97
)
19.3
8 (1
9.45
)
15.2
5 (1
5.31
)
12.1
5 (1
2.22
) 10
.01
(10.
15)
10.9
1 (1
0.99
) 16
.31
(16.
39)
18.3
0 (1
8.38
)
14.8
5 (1
4.91
)
22.7
5 (2
2.87
)
18.7
3 (1
8.87
)
16.1
0 (1
6.15
) 22
.37
(22.
45)
27.4
8 (2
7.53
) 19
.69
(19.
80)
16.1
2 (1
6.05
)
12.7
0 (1
2.99
)
10.0
0 (1
0.20
)
16.3
9 (1
6.29
)
13.5
9 (1
3.53
)
14.7
6 (1
4.65
) 21
.78
(21.
86)
16.4
0 (1
6.25
)
13.3
7 (1
3.25
)
15.2
8 (1
5.17
)
12.6
5 (1
2.53
)
14.7
2 (1
4.65
)
19.8
1 (1
9.95
) 18
.45
(18.
35)
17.7
1 (1
7.60
)
21.5
1 (2
1.40
)
21.9
1 (2
1.58
)
38.6
0 (3
8.2 8
)
18.2
1 (1
8.01
) 33
.76
(33.
84)
28.4
7 (2
8.39
)
18.1
5 (1
8.03
)
33.0
5 (3
3.14
)
16.9
7 (1
6.88
) 31
.41
(31.
22)
21.9
0 (2
1.78
)
10.5
1
(10.
45)
21.3
1 (2
1.40
)
330
325
1 30
b
1 30b
12Sb
260
25 8
254
253
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Tabl
e 1
ant.
29.
Co(
NM
ATU
),
30.
Co(
NEA
TU),
31.
Pd(H
ATU
),Cl,H
,O
32.
Pd(H
ATU
),Br,
H,O
33.
Pd(H
NM
ATU
),Cl,H
,O
34.
Pd(H
NM
ATU
),Br,H
,O
35.
Pt(H
NM
ATU
),Cl,
36.
Pt(H
NM
ATU
),Br,
37.
Pd(H
SEA
TU)C
l, 2H
,O
38.
Pd(H
SEA
TU)B
r, 2H
,O
39.
Pt(H
SEA
TU)C
l,
40.
Pt(H
SEA
TU)B
r,
Cho
cola
te
Cho
cola
te
Ligh
t bro
wn
Ligh
t bro
wn
Ligh
t bro
wn
Ligh
t brown
Ligh
t yel
low
&ht
ye
llow
Ora
nge
yello
w
Ora
nge
yello
w
Ora
nge
Ora
nge
13.1
1 (1
3.05
) 11
.81
(1 1.
94)
24.7
5 (2
4.66
)
18.6
2 (1
8.45
) 23
.40
(23.
26)
19.6
0 (1
9.47
)
36.7
2 (3
6.79
)
3 1.6
2 (3
1.50
)
29.7
0 (2
9.49
) 23
.91
(23.
72)
45.3
9 (4
5.34
) 38
.80
(3 8.
92)
37.1
0 (3
7.16
) 34
.1 1
(34.
00)
25.8
7 (2
5.96
)
19.3
9 (1
9.43
) 24
.60
(24.
48)
20.6
1 (2
0.49
)
21.1
9 (2
1.13
)
17.2
1 (1
8.09
)
15.4
1 (1
5.58
) 12
.57
(12.
48)
13.2
0 (1
3.22
) 1 1
.20
(11.
17)
23.8
1 (2
3.89
) 29
.19
(29.
1 4)
11.0
1 (1
1.12
)
9.14
(9
.22)
15.5
8 (1
5.67
)
13.0
0 (1
3.1 2
)
13.6
2 (1
3.58
)
11.5
1 (1
1.63
)
13.4
1 (1
3.35
) 10
.59
(10.
70)
11.5
3 (1
1.65
) 19
.63
(9.5
8)
21.3
3 (2
1.23
) 19
.52
(19.
43)
14.9
2 (1
4.83
)
11.2
1 (1
1.10
)
14.0
7 (1
3.99
)
11.6
2 (1
1.71
)
12.2
1 (1
2.07
)
10.4
2 (1
0.33
)
8.79
(8
.96)
7.
19
(7.1
0)
7.61
(7.49
6.35
(6
.38)
16.5
5 (1
6.45
)
27.8
9 (2
7.75
)
15.6
3 (1
5.52
)
29.3
5 (2
9.28
)
13.4
9 (1
3.39
)
25.9
1 (2
5.84
) 19
.85
(19.
75)
35.7
9 (3
5.68
) 16
.62
(1 6.
51)
c
m
m
215
n
21 7
ff 21
0 3 *
'The
oret
ical
val
ues g
iven
in p
aren
thes
es.
met
hano
l. A
ll ot
her c
ondu
ctan
ce m
easu
rem
ents
in H
,O a
t 25"
.
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THIOUREA COMPLEXES 167
dropwise to a suspension of Ni(SEATU)13 (5 g) in water (100 cm3) at 80" with con- tinuous stirring. When moet of the suepension had dissolved, the mixture waa flltered and the filtrate produced orange crystals of the subject compounds on aerial evaporation. Ni(HSE4 TU),SO4H1 0 separated out in the form of fme crystals on treating the aqueous solution of the complex chloride with sodium sulphate. The complexes were washed with water and dried over CaCl1.
Cbpper(II) Complexes
C!A(ATU)~. A methanolic solution of CuCll (0.01 mole, 25 cm') WM slowly added to that of HATU (0.04 mole, 100 cm3) containing sodium hydroxide pellets (1.5 g) at 0'. At first, a brown precipitate appeared which dissolved slowly on shaking, producing a rose-red solution. It was filtered quickly and the filtrate produced rose-red crystals, within half an hour. cu(HsEATU)lXl (X = Cl, Br) and CyHSEATU)1SO&O were isolated following the method of preparation of the corresponding nickel(I1) complexes.
Dropwise addition of appropriate halo- acides (1 :1) to an aqueous solution of CU(HSEATU)lXl (X = Cl, Br) tumed the rose-red colour of the solution slowly to blue. The addition of the haloacid was continued until the blue colour of the solution became most intense (pH - 4.0). The clear filtrate was allowed to evaporate in an atmosphere of the corresponding hydrogen halide in a desic- cator. Blue crystals of [Cu(HSEATU)(HIO)l] Xl (X = Cl, Br) separated out from the solution within 4 days. These were washed with methanol and dried over CaCll.
[Cu(HSEATU)(H20J21Xl (X = CIS Br).
CobaldIII) Complexes Orange CO(ATU),15H20 (compound 11). A saturated aqueous solution of (CO(NH~)~]C~, (0.01 mole) was mixed with a saturated methanolic solution of the ligand (0.05 mole). A brown precipitate of Co(ATW3 (SN bonded) appeared within 30 minutes. The mixture was then treated with sodium hydroxide pellets (4 g) and kept for 24 hrs. During this time most of the brown precipitate dissolved to produce a deep orange solution. It was heated at 60' on water bath for 20 minutes and filtered quickly. The filtrate produced orange crystals of the compound on concentration in a vacuum dessiccator. The diaquocomplex (compound 12) was obtained by heating a saturated aqueous solution of CO(ATU)~~.SH~O (0.01 mole) with N&C1 (0.05 mole) at 80' on water bath for 30 minutes. This was filtered hot and the filtrate produced orange crystals of the subject compound on cooling.
[Co(SEA TV), (OH)(Hl O)] . Passage of air through an aqueous suspension (100 cm' ) of C o ( S E A m 3 (0.01 mole) for 6 hrs produced an orange solution. This was filtered and the filtrate produced orange crystals of (Co(SEATU),(OH)(HlO)] on vacuum evaporation. For the preparation of complex halides (compounds 14 and IS), saturated aqueous solutions of [Co(SEATU)2(OH)(HS0)] (0.01 mole) were heated with the appropriate ammonium halide (0.05 mole) on a water bath for 30 minutes. The solution gave crystals of the complex halides on aerial evaporation.
Synthais of SN bonded complexes.
Nickl(U) Complexes Ni(HATU)lXl (X = CIS Br, NO3). Saturated acetone solutions of the appropriate nickel@) d t r (0.01 mole) were thoroughly mixed with tho@ of HATU (0.04 mole) at 0'. The mixture was filtered immediately and the fdtrate produced red crystals of
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168 CHITTA R. SAHA AND NITISH K. ROY
the subject compounds within 30 minutes. The crystals were washed with acetone and dried over CaC12. Ni(AT(I)2 (compound 19) was prepared by treating a methanolic solution of Ni(HATUhC12 with dilute sodium hydroxide in methanol. The mixture was filtered immediately and the filtrate produced silky red crystals of the subject com- pound within 5 minutes.
Aqueous solutions of the appro- priate nickel(I1) halide 50 cm3, 0.01 mole) and the ligand (50 cm', 0.04 mole) were mixed together and heated at 80' on a water bath for 15 minutes. The clear filtrates produced red crystals of the desired compounds on vacuum evaporation. The complex sulphate (compound 24) and the innter complexes (compounds 25 and 26) precipipated out in the form of fine crystals on treating aqueous solutions of the corresponding complex chlorides with sodium sulphate and sodium hydroxide solutions, respectively. The precipitates were thoroughly washed with water and dried over CaC12.
NiL2X, (L = WMATU, HNEATU, X = Cl, Br).
&pper(II) Complexes
Cu(HL), X2 (L = NMA TU; X = F, %SO4). An aqueous solution (50 an3) of HNMATU (0.04 mole) was rapidly added to a well-stirred aqueous solution of the corresponding Cu(I1) salt at room temperature. Bluish-pink crystalline precipitates were obtained in both cases. These were filtered, washed and dried as usual.
Cobalr(III) complexes. G3L3 ( L = NMATU, NEATU). A saturated aqueous solution of C O ( N H ~ ) ~ C ~ ~ (0.01 mole) was mixed with a saturated methanolic solution of the ligand (0.06 mole) at room temperature. The solution was made alkaline (PH 12) with sodium hydroxide and kept. in a desiccator for 3 days. The colour of the solution became deep brown. It was fdtered, and the filtrate on evaporation produced deep brown crystals of the desired compound. These were purified by recrystallization three times from methanol.
PalWiium(ll) and Platinum(II) complexes The Palladium(I1) complexes (compounds 3 1-34) were obtained by adding an aqueous solution of the ligand (0.01 mole) to that of PdXi (0.001 mole, X = Cl, Br) at 50 to 60'. The resulting solution was filtered and the filtrate produced light brown crystals of the desired compound on evaporation. Other complexes of palladium(I1) and platinum(1I) (compounds 35-40) were isolated in 1 : 1 haloacid medium following the above procedure.
RESULTS AND DISCUSSION
Different types of complexes with these ligands have been synthesized both in aqueous and nonaqueous media. The ligands behave both as NN and SN donors depending on the experimental conditions and the pH of the medium. NN bonded complexes were isolated under alkaline conditions while the SN bonded complexes were obtained at neutral or slightly acidic pH. Palladium@) and platinum(I1) always form SN bonded complexes.
NN bonded complexes. The colours and roperties of these complexes are comparable to those of the correspon- ding biguanides! Inner complexes of nickel@), copper@) and cobalt(II1) with HATU were isolated from aqueous or methanolic solutions under highly alkaline conditions. The
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THIOUREA COMPLEXES 169
complexes are stable towards water or cold alkali, but are decomposed by hot strong base. The ligands themselves, however, decompose under these conditions. Attempts to convert the inner complexes to the corresponding cationic ones by the addition of dilute HX or N h X (X = Cl, Br, 1/2S04) under different experimental conditions were unsuccessful and led to metal-ligand bond rupture. Warm N&Cl solutions convert Co(ATW3 to [CO(ATU)~(H~O)~] Cl and the latter forms [Co(ATU),(OH)(H20)] with dilute alkali.
Inner and cationic complexes of HSEATU were synthesized in ammoniacal and slightly acid solutions, respectively. Attempts to synthesize [Co(HSEATW3 ] X3 (X = CI, Br, %SO4) or CO(SEATU)~ in the presence of excess ligand under different experimental conditions were unsuccessful and led to the isolation of bischelate com- plexes. A pH dependent equilibrium (1) operates in the case of the copper(11) complexes and mono- and bis-chelates were isolated at ph = 3 and = 7 respectively. Their properties are comparable to those of correspondmg copper(I1) biguanides."
H+ O H (1) L Cu(HSEATU)z Xz 7 [Cu(HSEATU) (HZO),] X? + HaSEATUC
SN bonded complexes. The physicochemical properties of these complexes are different from those of the NN bonded species. The conductances of the deep red diamagnetic complexes Ni(HATU)2X2 (X = Cl, Br) in methanol indicate them to be 2:l electrolytes. HNMATU and HNEATU also form red diamagnetic nickel(I1) complexes in water which are more stable than Ni(HATU)2 X2.
The pink complexes Cu(HNMATU)2X2 (X = F, %SO4) were prepared in neutral aqueous solution. Isolation of these complexes was possible due to their high insolubilities. Preparation of copper(I1) complexes with X = CI, Br was not possible due to reduction of Cu(I1) to Cu(1) by these thioligands.' The water-insoluble reddish-brown complex, CO(ATU)~ .3H2 0 was converted to the corresponding cationic one, CO(HATU)~(SO~)~,~. DMSO by (NH4)2S04 in DMSO. These two compounds are, however, decomposed to CoS by hot alkali. The inner complexes CO(NMATU)~ and Co(NEATW3 were converted to their corresponding complex chlorides by dilute ammonium chloride solution.
Complexes M(HL)?X2 (M = Pd, Pt; L = ATU, NMATU, X = Cl, Br) are soluble in water and stable towards dilute acid. They are decomposed to metal sulphides by warm alkali. Their conductances in water show them to be 2:l electrolytes. The monochelates M(HSEATU)X2 (M = Pd, Pt; X = Cl, Br) were isolated from acid solution. Attempts to synthesize the corresponding bischelate or inner complexes in the presence of excess ligand under different experimental conditions were unsuccessfid.
General characteristics of the complexes. Except the NN bonded complexes of HATU and SN bonded complexes of HSEATU with Pd(I1) and Pt(II), all species can be obtained both in inner and cationic forms according to equation (2).
The complexes are decomposed by strong acids or alkalies. The inner complexes are insoluble in water, methanol etc., while the corresponding cationic ones are soluble in
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170 CHI'ITA R. S A W AND MTISH K. ROY
these solvents. Conductance data, conductmetric titrations and magnetic moments of these compounds agree with their formulae as given in Table 1. The SN bonded com- plexes are decomposed easily to metal Aphides by alkali while the NN bonded com- plexes a n decomposed to metal hydroxide under the same conditi0ns.N-alkyl-l-amidino- 2-thioureas were always found to behave as SN donors. Isolation of their NN bonded complexes was not possible.
Infiared spectra
The assignment of some important ir bands of these complexes have been made (Table 2) after due consideration to similar c ~ m p o u n d s . ~ ~ ~ * ~ ~ ~ * - ~ ~ Absence of any bands in the region 2600 to 2000 cm-' in neutral or monobasic salts of the ligands probably indicates the absence of the -SH group. The UN-C-N bands are split in the NN bonded complexes (compounds 2-4 and 12-14; Table 2) but not in the SN bonded ones (compounds 5,6, 8-10; Table 2). The most characteristic differences between the spectra of NN and SN bonded complexes are that, in the former, the bands due to V N - ~ - S (3s and YC-S remain almost unchanged relative to those in the free ligands and only one new band appears at - 500 cm" due to U M - N . In the latter, the first two bands i.e. qq-c-s (3) and uc-s undergo appreciable lower frequency shifting and two new bands at - 500 cm-I (due to YM-N) and - 350 cm-I (due to Y M ~ ) appear. The positions of the bands appear to be insensitive to the nature of the metal atoms. In M(HSEATU)C12 (M = Pd, Pt), the vC- band shows an appreciable red shift and two new bands at - 490 (VM-N) and - 360 cm- (YM-S) are observed. All these observations suggest SN bonding in these complexes.
s
Electronic spectm Electronic spectral data for the complexes in the solid state and in solution are presented in Table 3. The striking resemblance of the d-d band positions of the nickel(I1) (compounds 1 -6), copper@) (compounds 19-25) and cobalt(II1) complexes (compounds 28-3 1) to those of the corresponding metal biguanides suggests 12,24"*" the presence of NN bonding and strong chelate ring currents. The spectra of the other nickel(II) (compounds 7-1 2), copper(II) (compounds 26,27), cobalt(II1) (compounds 32-34) and palladium(II) complexes (compounds 15-18) are completely different from those of the NN bonded ones and indicate SN bonding. The spectra of the NN bonded nickel(II) complexes are consistent with the energy level diagram for square- planar complexes with delocalized n-electron systems" as only two d d bands are observed in compounds 1-6. In the SN bonded complexes (compound 7-12,14-16), the appearance of three d-d bands may be due to a lower symmetry of coordination. Assigning the flnt band to the All + ' BU (xy + x2-y2) in-plane transition, the orbital splitting parameters were calculated assuming a correction factor2' (Fz = 10F4 = 800 cm-I for nickel(II) and 600 cm-' for palladium(1I)) for both SN and NN types of complexes. The results show A,(") > AI(SN) for nickel@) and Al(Pd) > Al(Ni) for the SN bonded complexes. For L + M charge transfer bands, the relation CT(Pd)> CI'(Ni) also holds good.n*u The Al values for SN donor complexes ofnickel(II)(- 21,00O~m-~) and palladium(n) (- 23,000 cm-' ) place these ligands in the following SN donor spectro- chemical series: dithiooxamide > N, N-dimethyldithiooxamide > HATU > HNMATU > dithiomalonamide > diphenyldihiomalonamide.=
CI then X = Br are in accordance with the relative positions of the halogens in the spectro- chemical series and support the presence of coordinated halogen in the complexes.
For the orange cobalt(m) complexes, relatively high values of 10 Dq and low values of fl indicate the presence of extensive metal ligand n-bonding. The splitting of the
For Pd(HSEATU)XZ and Pt(HSEATU)X2 (X = Cl, Br), higher A1 values for X
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TAB
LE 2
l
nf
d sp
ectr
al data f
or s
elec
ted
com
plex
es; an-'.
Compound
6H,O
6m
W
C-N
W
C-S
(l)
vN
Cs
(2)
WC
S(3
) "C
-s
"M-N
"M
S
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
HA
TU
NY A
TU) , .1
.S H
, 0
1710
va
Co(
ATU
),.l.S
H,O
17
15s
Cu(
HSE
ATU
(&O
), Cl,
1670
s
16
45
~
16
40
~
1645
vs
164O
vs
16
50
~
16
45
~
16
60
~
1655
vs
1650
1660
-
1645
-
1560
s
164O
va
1040
vs
16
15
~
15
25
~s
1610
- 1
57
0~
15
20s
1615
vs
1575
- 1
52
0~
1
61
0~
1
58
0~
s 15
1ovs
16
10-
15
80
~s
16
10
~s
1s
m
1620
vs
1510
n 16
1On
1535
n 16
15-
15
30
~
16
20
~
15
50
~s
1590
s 15
35s
1500
s 15
90
1570
s 15
20s
1600
s 15
80s
1520
s 15
50s
15
30
~
144o
ms
144o
ms
1435
111s
1440
s
1440
ms
1430
ma
1425
ms
1450
s
1440
s
1450
s
1370
11s
935s
1370
s 93
0s
1380
s 93
0s
1370
s 93
0s
1325
s
1360
s 87
0w
1335
ma
820s
13
50m
840s
1350
11~
13
40s
960w
1360
s 85
Om
s 13
36s
1360
s 84
0m
1340
s 13
50s
84O
w
1300
s
800m
8lO
m
8151
11s
805
760s
715s
770m
710-
715m
700r
675s
670w
670
675
645-
510s
460s
33
5w
5OOS
36
0w
460s
34
0w
850s
34
0w
470w
36
5w
510s
50
0s
485s
890w
48
0s
490s
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TABL
E 3
Ekctronic spectral data f
or th
e co
mpl
exes
.' Cha
rge transfer bands
gl(cm-1)
Compound
dd
bands (cm"
X IO-')
(an-'
x 10
-1)
y, (a-')
1.
Ni(Hbg),cIz
21.74(2.05), 24.10(2.0)d1
35.71(3.4)
24,540
2.
Ni(ATU2
22.47(2.08), 24.39(2.02)sh
35.71( 3.48)
3.
Ni(SEATU),
20.15(2.05), 23.81(2.32)
34.84( 3.47), 37.04( 3.85)
2295
0 4.
Ni(HSEATU),Cl,
25,270
0
20.16(2.09), 23.69(2.32)
33.78(3.48). 38.46(3.89)
22,960
* 5.
Ni(HSEATU),Br,
20.16(2.04), 23.63(2.33)
33.68(3.45). 38.21(3.8Z)
22,960
?
6.
NI(HSEATU),
I, 20.08(2.04), 2358( 2 32
) 33.68(3.46), 38.12(3.85)
22,880
>
7.
NI(ATU),~
17.86(1.83), 20.41(1.94),
22.73( 1.97)
35.71(3.31)
20,660
T 18.04(1.78), 20.01(1.93), 23.25(1.92)
31.05(3.35), 35.82(3.86)
20,840
z 10.
Ni(NMATLOlb
18.12(1.84), 20.06(1.99), 22.73t2.00)
31.75(3.33), 36.36(3.48)
20,9 20
3 11.
NYHN
MATU
), Cl,
18.02( 1.82), 20.1 6(2.00), 22.72( 1.99)
31.25(3.31). 36.36(3.52)
20.820
E T: 26,490
.( 9 $ V
J
8.
Ni(HATU),CL,
18.00(1.76), 20.01( 1.92), 23.23 1.95)
31.02(3.34). 35.71(3.92)
20,800
9.
Ni(HATU),Br,
7c
12.
Ni(HNMATU),Br,
18.02(1.84), 20.06(2.00), 22.68(2.00)
31.2X3.34).
36.36(3.50)
20,820
13.
Pd(bglld
24.39
28.27
14.
Pd(A
TUad
21.06
24.40
27.78
32.72
37.76
23,160
15.
Pd(HATU, Cl,
21.00
24.38
27.8 1
32.71
37.82
23.100
16.
Pd(HNMATU), CLd
21.02
24.33
27.40
32.29
23,120
17.
Pd(HSEATU)CJd
2 1.04
24.39
27.78
37.08
23.140
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Table 3 wn
t.
37.08
21,330
18,
Pd(HSEATU)Brad
19.23
25.00
27.77
19.
Cu(bgIzd
17.84931
20.40
20,
Cu(Hbg), c1,
18.76
21,
Cu(HSEATU),CL,
18.69
28.22
22,
Cu(ATU),
18.69
28.22
23,
Cu(Hbg)(H,O),CL,
15.25
24.
Cu(HSEATU) (H,O),C4
15.38
28.56
25.
Cu(HSEATU) (H,O),Br,
15.38
28.56
26.
Cu(HNMATU),
F,d
16.52
18.34
27.03
27.
Cu(HNMATU),
SO,d
16.66
18.18
27.03
28.
Cu(Hbg),C!,
20.80(1.87), 27.0m2.01)
29.
29.
CO(ATU),~
21.05(1.82), 28.16(2.04)
33.3 3(
3 .O 1)
30.
Co(Hbg), (H,O), Cl,
16.66(0.18) 21
.05~
.98). 28.17(2.05)
31.
CO(ATU),(H,O),C~~
16.64(0.17)
20.60( 1.921, 28.15u.98)
33.33(3.02)
32.
Co(ATU),'
20.10(1.89)
29.41M2.98)
33.
Co(NMATU),
20.15(1.92)
29.62W3.10)
34.
Co(NEATU),
20.16(1.95)
29.62W3.15)
aFigures in the parentheses indicate log c
val
ues. The spectra wm
e recorded in methanol unless mentioned o
ther
wis
e. b
in DMSO. 'in
isobutanol
dreflectance spectra. 'in
DMF. fin H,O. gcalculated a
ssum
ing C
= 4B
, and E
('A,,-
+ 'Td
= 10Dq +
8B - 3C.
I OD@
22,350
22,830
25.580
25,610
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174 CHITTA R. SAHA AND NITISH K. ROY
'A, --* 'A, band due to trms-H20 molecules was not observed. The bands at - 16,650 cm-' for compounds 30-31 are assigned to Al, + 'TZp transitions due to their very low intensity. In Co(ATU), , the ' A, -, ' T, absorption 1s masked by intense charge transfer bands.
Nmr studies.
The pmr spectral data of some of the nickel@) and cobalt(II1) complexes are presented in Table 4 and the assignments have been made with reference to Ni(Hbg)2C12.12 The spectra can be explained on the basis of the suggested structures in Figure 1. The signals appearing in the range of 0-2.5 T in compounds 1,2,4,6 and 8 are due to the bprotons. This indicates the planarity of the metal-ligand ring and the presence of strong chelate ring currents in these complexes. In the orange inner complexes of nickel(II) and cobalt(II1) (compounds 2 and 8 respectively) the presence of signals in this range is in accordance with their NN bonded structures (Fig. lc). The absence of this signal m) in the inner complexes of N i ( A w 2 (compound 3). Ni(SEATW2 (compound 5 ) and Co(ATU), (compound 7) and its presence in their corresponding cationic complexes (compounds 4 and 6) support the suggested structures shown in Fig. l e for compounds 3 and 7, Fig. lg for compound 5 , Fig. Id for compound 4 and Fig. l h for compound 6 (Table4). Splitting of the He proton signals in compounds 3 and 7 is due to their unsym- metrical structures (Fig. le). Protons corresponding to 02, being nearer to less electro- negative ring sulphur atoms will be slightly more shielded than protons. Similar split- tings of the NH, protons and upfield shifting of H(az) relative to H(al) in compounds 2 and 8 can be explained by the inductive effect of the sulphur group (Fig. le). This split- ting does not occur in symmetric structures of Ni(Hbg)2C12.12 The pmr signals of Pd(HSEATU)C12 and Pd(HNMATU)zC12 could not be properly assigned due to over-
TABLE 4 Pnu spectral data for selected compkncer
Compound CH, a, HQ Ho H, I . Ni(Hbg),Cl, - - 5.35(2) 3.4(4) 0.12(1)
broad narrow broad 2. Ni(ATU), - - 4.8(a1 ,1) 4.2(2) 0.8(1)
5 . 2 ( ~ , ,1) m o w broad
broad 4.4(81,2) 3. Ni(ATU), - - 5.8(1) 3.4(81,2) -
nanow 4. Ni(HATU),CI, - - 5.6(1) 3.4U1 ,2) 0.6(1)
broad 4 . 0 ~ 3 ~ ,2) narrow
4.9(2) 4.0(2) - broad narrow
broad narrow broad
Very broad 3.9(8,2)
broad narrow broad 5.4(Q, ,I) narrow
5. Ni(SEATU), 8.7(t,3) 6 . W -2)
6. Ni(HSEATU),Cl, 8.8(t,3) 6.8(q92) 4.8(2) 3.6(2.1) 2.1(0.8)
7 . Co(ATU), - - 5.6(1) 3.4(01 $2) -
8. Co(ATU), - - 4 . 8 ( ~ , ,1) 3.8(2) 1.2(1)
'Recorded in d'-DMSO; Figure in parentheses indicate relative intensities; t = triplet, q = quartet.
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THIOUREA COMPLEXES 175
R = H, HATU (R - H) R CH3, HNMATU R = CzH6. HNEATU
iaI (b)
J Mn+ n*
OH- - 7
ETS
'??- -NH /;---- + Mn* N !
\ * - - - -
,>c- N H ~
HZN HSEATU
[i
FIGURE 1
lapping and broad peaks. However, the absence of any proton signals in the range 0-3.0 r in the former and their presence at 1.4 7 in the latter, supports the suggested structures, Fig. l i and Fig. Id, respectively.
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176 CHIITA R . SAHA AND NITISH K . ROY
Thermal analyses. The lattice water molecules are generally lost in the temperature range 80 to 120'. Higher temperatures (1 20 to 150') required for the dehydration of orange Ni(ATU)? .1 .5H20, orange Co(ATU)3.1 .5H20 and chocolate Co(ATU)3 .3H20 and the complex sulphates (Table 1) indicate the possibility of strong hydrogen bonding between H20 and the ligand or sulphate ions as the case may be. The diaquocomplexes of copper(I1) and cobalt(II1) lose coordinated H20 molecules in the temperature range 1 50-200' with partial decompositions.
The suggested structures of these complexes shown in Fig. 1 can explain all of their physicochernical properties. The presence of chelate ring currents in these complexes is responsible for their high stabilities. Conversion of the inner complexes to the corres- ponding complex salts via protonation of ligand nitrogen atoms is only possible if the n-electron delocalization is preserved. This happens through the protonation of the N3 atom in case of metal complexes of HSEATU (Figs. le and Id) and HNMATU (Figs lg and lh). NN bonded inner complexes of HAW, on the other hand, cannot be converted to the corresponding cationic ones because protonation of any ligand nitrogen atom destorys the welectron delocalization either partially or completely (Fig. le). Non- existence of inner complexes such as M(HSEATU)X2 (M = Pd, Pt; X = c1, Br) must be due to absence of 4 protons in their structures (Fig. li).
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