Versatility of heterocyclic thioamides in the construction of a trinuclear cluster [Cu3l3(dppe)3(SC5H 4NH)] and Cu1 linear polymers {Cu6(SC 5H4NH)6i6}n· CH3CN and {Cu1S(SC3H6N 2)6X6

Article abstract of DOI:10.1021/ic0484809

Reaction of copper(I) iodide with pyridine-2-thione (2-SC₅H ₄NH) and 1,2-bis(diphenylphosphino)ethane (dppe) in a CH ₃CN-CHCl₃ mixture yielded a triangular cluster, [Cu ₃l₃(μ₂-P,P-dppe)₃(η ¹-SC₅H₄NH)], 1. Similar reaction with 2-SC ₅H₄NH and a series of diphosphanes, Ph₂P-X- Ph₂P {X = -CH₂- (dppm), -(CH₂)₃- (dppp), -(CH₂)₄- (dppb), -CH=CH- (dppen)}, gave a novel iodo-bridged hexanuclear Cu¹ linear polymer, {Cu₆(μ₃-SC₅H₄NH) ₄(μ₂-SC₅H₄-NH)₂(I ₄)(μ-I)₂-}_n·2nCH₃CN, 2. Reactions of copper(I) iodide/copper(I) bromide with 1,3-imidazolidine-2-thione (SC₃H₆N₂) in a CH₃CN-CHCl ₃ mixture yielded hexanuclear Cu¹ linear chain polymers, [{CU₆(μ₃-SC₃H₆N₂) ₂(μ₂2-SC₃H₆N₂) ₄X₂-(μ-X)₄}_n] (X = Br, 4; I, 5). In compound 1, two iodide atoms and one dppe form the dinuclear Cu(μ₂-I)₂(μ₂-dppe)Cu core, and two dppe ligands bridge this core with the third Cu(I) center coordinated to 2-SC ₅H₄NH via the S atom. The chain polymer 2 has a centrosymmetric hexanuclear central core, Cu₆S₆I ₄(μ-I)₂-, formed by dimerization of six-membered trinuclear motifs, Cu₃(μ₂-SC₃H ₆N₂)₃I₃ via (μ₃-S) bonding modes of the thione ligand, and has four terminal and two bridging iodine atoms in frans-orientations. Linear chains are separated by the nonbonded acetonitrile molecules. In 4 and 5, three copper(I) bromide or copper(I) iodide moieties and three SC₃H₆N₂ ligands combined via bridging S donor atoms to form the six-membered trinuclear Cu ₃(M₂-SC₃H₆N₂) ₃l₃ cores which polymerized via S and X atoms in a side-on fashion to form linear chain polymers, [{Cu₆(μ₃- SC₃H₆N₂)₂(μ₂-SC ₃H₆N₂)₄X₂(μ-X) ₄}_n]. The (μ₃-S) modes of bonding of neutral heterocyclic thioamides are first examples, as are trinuclear cluster and linear polymers rare examples in copper chemistry.

Full text of DOI:10.1021/ic0484809

Inorg. Chem. 2005, 44, 1914−1921
Versatility of Heterocyclic Thioamides in the Construction of a
Trinuclear Cluster [Cu3I3(dppe)3(SC5H4NH)] and CuI Linear Polymers
Cu6(SC5H4NH)6I6}n‚2nCH3CN and (X Br, I)
CuI6(SC3H6N2)6X6
{
{
}
)
n
Tarlok S. Lobana,*,† Ritu Sharma,† Renu Sharma,† Sheetal Mehra,† Alfonso Castineiras,‡ and
Peter Turner§
Department of Chemistry, Guru Nanak DeV UniVersity, Amritsar-143 005, India, Departamento de
Quimica Inorganica, Facultad de Farmacia, UniVersidad de Santiago, 15782- Santiago, Spain,
and School of Chemistry, Crystal Structure Facility, The UniVersity of Sydney,
New South Wales 2006, Australia
Received October 30, 2004
Reaction of copper(I) iodide with pyridine-2-thione (2-SC5H4NH) and 1,2-bis(diphenylphosphino)ethane (dppe) in a
CH3CN CHCl3 mixture yielded a triangular cluster, [Cu3I3(µ2−P,P-dppe)3(
1-SC5H4NH)], 1. Similar reaction with
2-SC5H4NH and a series of diphosphanes, Ph2P Ph2P ) −CH2 (dppm),
CH CH (dppen)
, gave a novel iodo-bridged hexanuclear CuI linear polymer,
NH)2(I4)(
in a CH3CN
-X)4 n] (X
dppe)Cu core, and two dppe ligands bridge this core with the third Cu(I) center coordinated to 2-SC5H4NH via the
S atom. The chain polymer 2 has a centrosymmetric hexanuclear central core, Cu6S6I4( -I)2 , formed by dimerization
of six-membered trinuclear motifs, Cu3( 2-SC3H6N2)3I3 via ( 3-S) bonding modes of the thione ligand, and has four
−
η
−X−
{X
−
−
(CH2)3
−
(dppp), (dppb),
−
(CH2)4
−
−
d
−
}
{Cu6(µ
3-SC5H4NH)4(µ2-SC5H4-
µ
-I)2-}n‚2nCH3CN, 2. Reactions of copper(I) iodide/copper(I) bromide with 1,3-imidazolidine-2-thione (SC3H6N2)
CHCl3 mixture yielded hexanuclear CuI linear chain polymers, [
Cu6( 3-SC3H6N2)2( 2-SC3H6N2)4X2-
Br, 4; I, 5). In compound 1, two iodide atoms and one dppe form the dinuclear Cu( 2-I)2(µ2
−
)
{
µ
µ
(
µ
}
µ
-
µ
−
µ
µ
terminal and two bridging iodine atoms in trans-orientations. Linear chains are separated by the nonbonded acetonitrile
molecules. In 4 and 5, three copper(I) bromide or copper(I) iodide moieties and three SC3H6N2 ligands combined
via bridging S donor atoms to form the six-membered trinuclear Cu3(µ2−SC3H6N2)3I3 cores which polymerized via
S and X atoms in a side-on fashion to form linear chain polymers, [
The ( 3-S) modes of bonding of neutral heterocyclic thioamides are first examples, as are trinuclear cluster and
linear polymers rare examples in copper chemistry.
{Cu6(µ3-SC3H6N2)2(µ2-SC3H6N2)4X2(µ-X)4}n].
µ
Introduction
their chemical, biochemical, spectroscopic properties, and
structural diversity.2-13 Neutral pyridine-2-thione (structure
The importance of organosulfur compounds in chemical
and biological processes is well recognized, and such
compounds have been extensively studied.1 Heterocyclic
thioamides, bearing the functional group -N(H)-C(dS)-
T -NdC(-SH)-, constitute an important class of sulfur-
containing organic compounds that have been studied for
(2) (a) Raper, E. S. Coord. Chem. ReV. 1985, 61, 115. (b) Raper, E. S.
Coord. Chem. ReV. 1996, 153, 199. (c) Raper, E. S. Coord. Chem.
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475. (e) Akrivos, P. D. Coord. Chem. ReV. 2001, 213, 181. (f) Garcia-
Vazquez, J. A.; Romero, J.; Sousa, A. Coord. Chem. ReV. 1999, 193,
691.
(3) Su, W.; Hong, M.; Weng, J.; Liang, Y.; Zhao, Y.; Cao, R.; Zhou, Z.;
Chan, A. S. C. Inorg. Chim. Acta 2002, 331, 8.
* Author to whom correspondence should be addressed. E-mail:
tarlokslobana@yahoo.co.in. Fax: 91-183-2-258820.
† Guru Nanak Dev University.
(4) (a) Lobana, T. S.; Bhatia, P. K.; Tiekink, E. R. T. J. Chem. Soc.,
Dalton Trans. 1989, 749. (b) Lobana, T. S.; Bhatia, P. K. Ind. J. Chem.,
Sect. A 1990, 29, 1225.
(5) Karagiannidis, P.; Aslanidis, P.; Kessissoglou, D. P.; Krebs, B.;
Dartmann, M. Inorg. Chim. Acta 1989, 156, 47.
‡ Universidad de Santiago.
§ The University of Sydney.
(1) (a) Oae, S. Organic Sulfur Chemistry: Structure and Mechanism; CRC
Press Inc.: Florida, 1992. (b) Miller, A.; Krebs, B. Sulfur, Its
Significance for Chemistry, for Geo, Bio-, and Cosmosphere and
Technology; Elsevier: Amsterdam, 1984.
(6) (a) Lobana, T. S.; Castineiras, A. Polyhedron 2002, 21, 1603. (b)
Lobana, T. S.; Paul, S.; Castineiras, A. Polyhedron 1997, 16, 4023.
(c) Karagiannidis, P.; Hadjikakou, S. K.; Aslanidis, P.; Hountas, A.
Inorg. Chim. Acta 1990, 178, 27.
1914 Inorganic Chemistry, Vol. 44, No. 6, 2005
10.1021/ic0484809 CCC: $30.25
© 2005 American Chemical Society
Published on Web 02/19/2005

Versatility of Heterocyclic Thioamides
I, 2-SC5H4NH), the simplest prototype of heterocyclic
thioamides, and a sulfur-containing analogue of purine and
pyrimidine nucleobases, has shown two modes of bonding
(IIIA, IIIB) with CuI and several other metals.2 Mode IIIC
is first reported here for compound 2. Mode IIID with a µ4-S
mode of bonding of neutral 2-SC5H4NH has been shown with
silver(I) only.3 Similarly, neutral 1,3-imidazolidine-2-thione
(II, SC3H6N2) with the functional moiety -N(H)-C(dS)-
N(H)- can bind to a metal or a group of metals via η1-
S9-12 or µ2-S10,13 bonding modes, and it has shown first µ3-S
mode similar to IIIC for compounds 4 and 5 reported here.
SC5H4NH)2], 6 (dppe ) Ph2P-CH2-CH2-PPh2).7a The
reaction behavior of copper(I) iodide with 2-SC5H4NH in
the presence of diphosphanes is unknown, though a related
ligand, namely, pyrimidine-2-thione, in the presence of 1,3-
bis(diphenylphosphino)propane(dppp) formed monomers,
[Cu(X)(HpymS)(dppp)] (HpymS ) pyrimidine-2-thione) for
X ) Cl, Br, and an iodo-bridged dimer, [Cu2(µ-I)2(dppp)2],
for X ) I, with chelating dppp.7b Recently it was observed
that iodide and alkane spacers connecting Ph2P groups of
diphosphanes played an important role in forming unusual
CuI polymers with bis(diphenylselenophosphinyl)alkanes.14ab
To understand the complexity of the interaction of cop-
per(I) halides with heterocyclic thioamides, a series of
reactions of copper(I) iodide with pyridine-2-thione in the
presence of diphosphanes and of copper(I) iodide/copper(I)
bromide with 1,3-imidazolidine-2-thione in a mixture of
solvents have been carried out. In this paper we report
synthesis, spectroscopy, and X-ray crystallographic studies
of the triangular cluster, Cu3I3(µ2-dppe)3(2-SC5H4NH) 1,
linear chain polymers,{Cu6(µ3-SC5H4NH)4(µ2-SC5H4NH)2-
(I4)(µ-I)2-}n‚2nCH3CN 2 and [{Cu6(µ3-SC3H6N2)2(µ2-
SC3H6N2)4X2(µ-X)4}n] (X ) Br, 4, I, 5).14c The construction
of supramolecular metal complexes containing copper(I) and
silver(I) is a very interesting area, in view of formation of
unusual metal clusters and multidirectional networks, some
of which display conducting properties.14d
Pyridine-2-thiolate (2-SC5H4N-), and its substituted ana-
logues, can bind to a metal, or a group of metals, via a variety
of bonding modes in dimeric, tetrameric, and hexameric
complexes.8a-g This versatility of pyridine-2-thione is at-
tributed to the size of S atom and its proximity to the pyridyl
nitrogen.2,3 The large size of the S atom makes it easier to
adopt different angles at this atom in complexes, which is
necessary for different geometries. The coordination chem-
istry of anionic imdtH2 is limited, however.13
The reactions of pyridine-2-thione with copper(I) halides
in a 1:1 molar ratio gave insoluble products of composition
{CuX(2-SC5H4NH)}n with unknown structures.2,4 Phosphane
ligands depolymerize insoluble {CuX(2-SC5H4NH)}n com-
pounds into monomers, [CuX(PPh3)2(2-SC5H4NH)] (X ) Cl,
Br),4,5 or dimers [Cu2X2(µ-SC5H4NH)2(R3P)2] (X ) halide,
R ) Ph or tolyl group).6 Among diphosphane ligands, only
dppe formed a P,P′-bridged dimer, [Cu2Br2(µ-P,P-dppe)2(2-
Experimental Section
General Materials and Techniques. Copper(I) iodide was
prepared by the reduction of CuSO4‚5H2O using SO2 in the presence
of NaI in water.15a Bis(diphenylphosphino)methane(dppm), 1,3-bis-
(diphenyl-phosphino)propane (dppp), 1,2-cis-bis(diphenylphos-
phino)ethane (dppen), pyridine-2-thione (2-SC5H4NH), and 1,3-
imidazolidine-2-thione (imdtH2) were purchased from Sigma-
Aldrich, Ltd. 1,2-Bis(diphenylphosphino)ethane (dppe) and 1,4-
bis(diphenylphosphino)butane (dppb) were prepared from PPh3 by
the lithiation method.15b The elemental analyses (C, H, N) were
obtained with a Carlo-Erba 1108 microanalyzer from University
of Santiago, Spain. The melting points were determined with a
Gallenkamp electrically heated apparatus. IR spectra were recorded
using KBr pellets on a FTIR-NICOLET 320 Fourier Transform
Spectrophotometer in the 4000-400 cm-1 range. 1H NMR spectra
of complexes were recorded on an AL-300 FT JEOL spectrometer
operating at a frequency of 300 MHz in CDCl3 with TMS as internal
reference.
Cu3I3(dppe)3(2-SC5H4NH), 1. To a solution of copper(I) iodide
(0.025 g, 0.13 mmol) in dry acetonitrile (5 mL) was added a solution
of pyridine-2-thione (0.015 g, 0.13 mmol) in acetonitrile (5 mL)
followed by stirring for 1 h when deep yellow colored precipitates
were formed. To these precipitates, a solution of dppe (0.052 g,
0.13 mmol) in acetonitrile-chloroform mixture (10 mL) was added
followed by stirring for 4 h. The light yellow colored solution
(7) (a) Cox, P. J.; Aslanidis, P.; Karagiannidis, P. Polyhedron 2000, 19,
1615. A. (b) Aslanidis, P.; Cox, P. J.; Divanidis, S.; Tsipis, A. C.
Inorg. Chem. 2002, 41, 6875.
(8) (a) Garcia-Vazquez, J. A.; Romero, J.; Castro, R.; Sousa, A.; Rose,
D. J.; Zubieta, J. Inorg. Chim. Acta 1997, 260, 221. (b) Kitagawa, S.;
Munakata, M.; Shimono, H.; Matsuyama, S.; Masuda, H. J. Chem.
Soc., Dalton Trans. 1990, 2105. (c) Block, E.; Gernon, M.; Kang, H.;
Zubieta, J. Angew. Chem., Int. Ed. Engl. 1988, 27, 1342. (d) Garcia-
Vazquez, J. A.; Romero, J.; Louro, M. L.; Sousa, A.; Zubieta, J. J.
Chem. Soc., Dalton Trans. 2000, 559. (e) Constable, E. C.; Elder, S.
E.; Palmer, C. A.; Raithby, P. R.; Tocher, D. A. Inorg. Chim. Acta
1996, 252, 281. (f) Perez-Lourido, V.; Garica-Vazquez, V.; Romero,
J.; Louro, M. S.; Sousa, A.; Zubieta, J. Inorg. Chim. Acta 1998, 271,
1. (g) Castro, R.; Romero, J.; Garcia-Vazquez, J. A.; Sousa, A.; Chang,
Y. D.; Zubieta, J. Inorg. Chim. Acta 1996, 245, 119.
(9) Al-Arfaj, A. R.; Reibenspies, J. H.; Isab, A. A.; Hussain, M. S. Acta
Crystallogr. 1998, C54, 51.
(10) Battaglia, L. P.; Corradi, A. B.; Nardelli, M.; Tani, M. E. V. J. Chem.
Soc., Dalton Trans. 1976, 143.
(11) Stocker, F. B.; Britton, D. Acta Crystallogr. 2000, C56, 798.
(12) Friedrichs, S.; Jones, P. G. Acta Crystallogr. 1999, C55, 1625.
(13) (a) Raper, E. S.; Wilson, J. D.; Clegg, W. Inorg. Chim. Acta 1992,
194, 51. (b) Jones, P. G.; Friedrichs, S. Chem. Commun. 1999, 1365.
(14) (a) Lobana, T. S.; Rimple; Castineiras, A.; Turner, P. Inorg. Chem.
2003, 42, 4731. (b) Lobana, T. S.; Hundal, G. J. Chem. Soc., Dalton
Trans. 2002, 2203. (c) Lobana, T. S.; Sharma, R.; Bermejo, E.;
Castineiras, A. Inorg. Chem. 2003, 42, 7728. (d) Munakata, M.; Wu,
L. P.; Kuroda-Sowa, T. AdV. Inorg. Chem. 1999, 46, 174
(15) (a) Handbook of PreparatiVe Inorganic Chemistry, 2nd ed.; Brauer,
G., Ed.; Academic Press: New York, 1965; Vol. 2. (b) Aguiar, A.
M.; Beisler, J. J. Org. Chem. 1964, 29, 1660.
Inorganic Chemistry, Vol. 44, No. 6, 2005 1915

Lobana et al.
Table 1. Crystallographic Data for Compounds 1, 2, 4, and 5
parameters
empirical formula
molecular mass
temp, K
cryst syst
space group
a, Å
1
2
4
5
C83H77Cu3I3P6NS
1877.65
C17H18Cu3I3N4S3
945.85
C9H18Br3Cu3N6S3
736.82
C9H18Cu3I3N6S3
877.79
293(2)
293(2)
triclinic
150(2)
triclinic
150(2)
orthorhombic
P2(1)2(1)2(1) (no. 19)
11.611(2)
23.191(4)
32.917(5)
90
triclinic
P1h (no. 2)
8.047(2)
13.454(3)
13.770(3)
64.097(3)
79.996(4)
81.448(4)
1316.1(5)
2
P1h (no. 2)
7.595(2)
11.968(3)
12.225(3)
68.016(4)
74.724(4)
87.670(4)
991.9(4)
2
P1h (no. 2)
7.883(2)
12.164(3)
12.615(3)
68.835(4)
73.432(4)
87.814(4)
1078.4(5)
2
b, Å
c, Å
R, deg
â, deg
90
90
8864(2)
4
1.406
1.929
γ, deg
V, Å3
Z
D
calc, Mg/m3
2.387
6.172
2.467
9.551
2.703
7.522
µ(Mo KR)/mm-1
no. unique reflns, Rint
no. of reflections
18160, 0.1258
6605
5354, 0.0459
3967
4589, 0.0381
4100
4872, 0.0514
4744
observed (I > 2σ(I)) final R indices
R1 ) 0.0724
wR2 ) 0.1624
R1 ) 0.0342
wR2 ) 0.0828
R1 ) 0.0225
wR2 ) 0.0539
R1 ) 0.0328
wR2 ) 0.0885
formed was allowed to evaporate at room temperature, and a light
yellow colored crystalline solid was obtained (yellow, 0.050 g, 60%,
mp 206-208 °C). Anal. Calcd for C83H77Cu3I3P6NS: C, 53.1; H,
4.10; N, 0.74. Found: C, 52.9; H, 3.94; N, 0.71. The complex is
soluble only in hot acetonitrile and poorly soluble in chloroform.
The crystals for X-ray study were grown from acetonitrile. IR bands
(KBr pellets): ν(C-S) 1133 (m), ν(N-H) 3165 (m), ν(P-CPh)
1097s cm-1. NMR data (δ, ppm; CDCl3): 2.62 (m, 12H, CH2),
6.62-7.62 (py + C6H5).
Cu6I6(2-SC5H4NH)6}n‚2nCH3CN}, 2. To a solution of copper(I)
iodide (0.025 g, 0.13 m mol) in dry acetonitrile (5 mL) was added
solid pyridine-2-thione (0.015 g, 0.13 mmol), followed by stirring
for 1 h, when deep yellow colored precipitates were formed. A
solution of 1,4-bis(diphenylphosphino)butane (dppb) (0.055 g, 0.13
mmol) in chloroform (10 mL) was added to the precipitates
followed by stirring for 2 h, when a bright yellow colored solution
was formed. The slow evaporation of the solution at room
temperature for 2 days with volume left to about 10 mL formed
yellow crystals of dimer 3a (see below) and the filtrate upon further
allowing it to evaporate at room temperature for overnight to volume
of mother liquor around 4-5 mL, gave crystals of polymer 2
(orange, 0.020 g, 45%, mp 140-142 °C). Anal. Calcd for C34H30-
Cu6I6N8S6: C, 21.57; H 1.90; N 5.92. Found: C, 21.84; H, 1.86;
N, 5.70. IR bands (KBr pellets): υ(C-S) 1130 (s), 1115 (sh), υ(N-
H) 3235 (w) cm-1. NMR data (δ, ppm; CDCl3): δ 7.56 (s, br),
7.47 (s, br, 3H, H-6), 7.28 (t, br, 3H, H-4), 6.95 (t, br, 3H, H-3)
6.60 (t, br, 3H, H-5), 13.20 (sb, 3H, NH), 2.01(s) (3H, CH3CN).
[Cu2(µ-I)2(dppb)2], 3a. Yellow-colored precipitates of 3a (0.036
g, 46%, mp 250-255 °C). Anal. Calcd for C56H56Cu2I2P4: C, 54.50;
H 4.54. Found: C, 54.03; H, 4.46.
Mp 180-185 °C. Anal. Calcd for C9H18Br3Cu3N6S3: C, 14.7; H,
2.44; N, 11.41. Found: C, 14.6; H, 2.44; N, 11.06. The complex is
very poorly soluble in CHCl3 and CH3CN. IR bands (KBr pellets):
υ(C-S) 1030 (m), 975(m), υ(N-H) 3290 (m), υ(C-N) 1510 (m)
cm-1. NMR data (δ, ppm, CDCl3): δ 6.52 (2H, NH), 3.79, 3.77
(4H, CH2). Ligand NMR data: δ 6.40 (2H, br. NH), 3.59 (4H,
CH2).
[{Cu6(µ3-SC3H6N2)2(µ2-SC3H6N2)4I2(µ-I)4}n] 5. A solution of
1,3-imidazolidine-2-thione (0.027 g, 0.26 mmol) in acetonitrile (10
mL) was added to a solution of copper(I) iodide (0.025 g, 0.13
mmol) in acetonitrile (10 mL), followed by stirring for 30 min at
room temperature. To this solution was added chloroform (5 mL)
and the contents stirred for a further period of 2 h. The slow
evaporation of the solution at room temperature to about 5 mL
formed white crystals of 5 (yield, 0.014 g, 35%). Mp 190-195
°C. Anal. Calcd for C9H18Cu3I3N6S3: C, 12.3; H, 2.04; N, 9.56.
Found: C, 12.9; H, 2.13; N, 9.91. The complex is very poorly
soluble in CHCl3 and CH3CN. IR bands (KBr pellets): υ(C-S)
1040 (s), 985(m), υ(N-H) 3160 (m), υ(C-N) 1465 (s) cm-1. NMR
data (δ, ppm, CD3CN): δ 7.03 (2H, NH), 3.69 (4H, CH2).
X-ray Crystallography. Data were collected using a Bruker
SMART CCD 1000 diffractometer, using graphite monochromated
Mo KR radiation (λ ) 0.71073 Å) from a sealed tube. The data
integration and reduction were undertaken with SAINT and
XPREP.16 A yellow plate crystal of 1 {or an orange needle crystal
of 2}was mounted on a glass fiber, and diffraction data were
collected at 291(2) K. A multiscan absorption correction using
SADABS was applied to the data for 1 and 2 (transmission factors,
0.910-0.658 for 1; 1.000-0.327 for 2 ).17 The structures of 1 and
2 were solved by the direct methods using the program SHELXS-
9718 and refined using SHELXL-97.19 The non-hydrogen atoms
were modeled with anisotropic displacement parameters, and in
general, a riding model was used for hydrogen atoms. N-H
hydrogen atoms for 1 and 2 were initially positioned at sites
determined from difference maps. Atomic scattering factors taken
[Cu2(µ-I)2(dppp)2], 3b. Mp 240-245 °C. Anal. Calcd for C54H52-
Cu2I2P4: C, 53.7; H, 4.31. Found: C, 53.0; H, 4.33.
[Cu2(µ-I)2(dppm)2], 3c. Mp 200-210 °C. Anal. Calcd for
C50H44Cu2I2P4: C, 52.2; H, 3.82. Found: C, 52.9; H, 4.01.
[Cu2(µ-I)2(dppen)2], 3d. Mp 205-210 °C. Anal. Calcd for
C52H44Cu2I2P4: C, 53.15; H, 4.30. Found: C, 53.30; H, 4.16.
[{Cu6(µ3-SC3H6N2)2(µ2-SC3H6N2)4Br2(µ-Br)4}n] 4. A solution
of 1,3-imidazolidine-2-thione (0.025 g, 0.25 mmol) in acetonitrile
(10 mL) was added to a solution of copper(I) bromide (0.018 g,
0.12 mmol) in dry acetonitrile (10 mL) followed by stirring for 30
min at room temperature. To this clear solution was added
chloroform (5 mL) and the contents stirred for a further period of
2 h. The slow evaporation of the solution at room temperature to
about 5 mL formed white crystals of 4 (yield, 0.012 g, 40%).
(16) Bruker. SMART, SAINT and XPREP. Area Detector Control and
data Integration and reduction Software; Bruker Analytical X-ray
Instruments, Inc.: Madison, WI, 1995.
(17) Sheldrick, G. M. SADABS. Program for Empirical Absorption
Correction of Area Detector Data; University of Goettingen: Ger-
many, 1997.
(18) Sheldrick, G. M. Acta Crystallgr., Sect. A 1990, 46, 467.
(19) Sheldrick, G. M. SHELXL-97. Program for the Refinement of Crystal
Structures; University of Goettingen: Germany, 1997.
1916 Inorganic Chemistry, Vol. 44, No. 6, 2005

Versatility of Heterocyclic Thioamides
Scheme 1
from “International Tables for X-ray Crystallography”,20 while
molecular graphics were taken from PLATON21 and SCHAKAL.22
Data for the isostructural complexes 4 and 5 were collected at
150 K, with crystal cooling in a cold nitrogen gas stream from an
Oxford Cryosystems Cryostream. A colorless prismatic crystal of
4 [or 5] attached with Exxon Paratone N to a short length of fiber
supported on a thin piece of copper wire inserted in a copper
mounting pin. A Gaussian absorption correction16,22b was applied
to the data in each case. The structure was solved by the direct
methods with SIR9716 and extended and refined with SHELXL-
97.19 The amine hydrogens were located and modeled with isotropic
displacement parameters. A depiction of the oligomeric structure
generated with ORTEP322c and showing 50% displacement el-
lipsoids is given in Figure 3. A summary of the crystal data,
experimental details, and refinement results are listed in Table 1.
The reaction of copper(I) iodide with pyridine-2-thione
in a 1:1 molar ratio in CH3CN formed an insoluble product
of empirical composition, {CuI(2-SC5H4NH)}n (presumably
a polymer of unknown structure), which reacted with dppe
in CH3CN-CHCl3 and formed an unusual triangular cluster,
Cu3I3(dppe)3(2-SC5H4NH) 1. The insoluble product {CuI-
(2-SC5H4NH)}n suspended in CH3CN reacted with dppb in
CHCl3 and formed a light-orange compound of the composi-
tion Cu3I3(2-SC5H4NH)3‚CH3CN (A), and X-ray crystal-
lography showed that it is a polymer, {Cu6I6(2-SC5H4NH)6}n‚
2nCH3CN (2, Figure 2). Other diphosphanes as listed in
Scheme 1 also formed polymer 2. Similarly, copper(I) iodide
and 1,3-imidazolidine-2-thione (SC3H6N2) in a 1:1 molar
ratio in acetonitrile formed an insoluble product of empirical
composition, {CuI(SC3H6N2)}n, (presumably a polymer of
unknown structure). This reaction carried out in a 1:2 molar
ratio (metal:ligand), followed by addition of chloroform-
yielded crystals of empirical composition, Cu3X3(SC3H6N2)3
(C), and X-ray crystallography showed that it existed as a
unusual CuI linear chain polymer, 5. Copper(I) bromide also
formed similar polymer, 4. In Scheme 1, B and D are
suggested as repeat units that formed polymers 2, 4, and 5.
Results and Discussion
Synthesis. Scheme 1 shows the formation of the triangular
cluster 1 and CuI-linear chain polymers 2, 4, and 5.
(20) International Tables for X-ray Crystallography; Kluwer Academic
Publishers: Dordrecht, The Netherlands, 1995; Vol. C.
(21) Spek, A. L.; PLATON. A Multipurpose Crystallographic Tool; Utrecht
University: Utrecht, The Netherlands, 2000.
(22) (a). Keller, E. SCHAKAL-97. A Computer Program for the Graphic
Representation of Molecular and Crystallographic Models; 1997. (b).
Coppens, P.; Leiserowitz, L., Rabinovich, D. Acta Cryst. 1965, 18,
1035. (c). Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565. (d).
Altomare A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.; Giacovazzo
C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R. J.
Appl. Cryst. 1999, 32, 115.
Structure of Triangular Cluster 1. In triangular cluster
1 (Figure 1, Table 2), two iodide atoms and one dppe ligand
form the dinuclear Cu(µ2-I)2(µ2-dppe)Cu core, and two dppe
ligands bridge this core with the third Cu(I) center to which
Inorganic Chemistry, Vol. 44, No. 6, 2005 1917

Lobana et al.
Table 2. Bond Lengths (Å) and Angles (deg) for Compounds 1, 2, 4,
and 5
Compound 1
Cu(1)-P(11)
2.238(5)
2.247(5)
2.700(2)
2.739(2)
2.260(5)
72.28(6)
72.00(6)
Cu(2)-P(31)
2.263(4)
2.703(2)
2.723(2)
2.281(5)
2.282(5)
2.707(2)
104.54(7)
104.89(7)
Cu(1)-P(21)
Cu(2)-I(2)
Cu(1)-I(1)
Cu(2)-I(1)
Cu(1)-I(2)
Cu(3)-P(32)
Cu(3)-P(22)
Cu(3)-I(3)
Cu(2)-P(12)
Cu(1)-I(1)-Cu(2)
Cu(2)-I(2)-Cu(1)
P(11)-Cu(1)-P(21)
P(12)-Cu(2)-P(31)
I(1)-Cu(1)-I(2)
130.19(17) I(1)-Cu(2)-I(2)
122.88(17) Cu(3)-S(1)-C(132) 113.7(8)
Compound 2
Cu(1)-S(1)
2.3060(15) Cu(2)-S(3)*
2.5871(16) Cu(2)-I(3)*
2.3005(15) Cu(3)-S(2)*
2.2970 (14)
Cu(1)-S(2)
2.5867 (9)
2.2750(15)
2.3134(15)
2.5776(9)
2.9094(10)
103.31(5)
76.64(5)
76.18(5)
125.17(6)
114.16(6)
Cu(1)-S(3))
Cu(1)-I(1)
2.5932(9)
Cu(3)-S(1)
Cu(2)-S(1)
2.5643 (16) Cu(3)-I(2)
2.3062 (15) Cu(3)-I(3)
Cu(2)-S(2)
S(1)-Cu(1)-I(1)
S(2)-Cu(1)-I(1)
S(3)-Cu(1)-S(1)
S(3)-Cu(1)-S(2)
S(3)-Cu(1)-I(1)
S(1)-Cu(1)-S(2)
119.59(4)
104.53(4)
110.09(5)
97.86(5)
118.08(5)
102.61(5)
S(1)-Cu(2)-S(2)
Cu(1)-S(1)-Cu(2)
Cu(1)-S(2)-Cu(2)
Cu(3)-S(1)-Cu(2)
Cu(3)-S(1)-Cu(1)
Compound 4
Figure 1. The structure of triangular cluster 1 with numbering scheme.
Cu(1)-S(1)
Cu(1)-S(3)
Cu(1)-Br(1)
Cu(1)-Br(1)*
Cu(2)-Br(2)
2.2842(9)
2.2910(9)
2.5525(6)
2.4839(6)
2.4359(6)
Cu(3)-Br(2)
Cu(3)-Br(3)
Cu(2)-S(1)
2. 4938(7)
2. 4631(7)
2.2758(9)
2. 3540(10)
2. 3483(9)
109.97(2)
one 2-SC5H4NH is also coordinated via an S atom. In the
dinuclear core, the Cu-I-Cu and I-Cu-I bond angles of
ca. 72 and 105°, respectively are close to the theoretically
predicted values6 of ca. 70 and 105°. Further, the Cu(1)‚‚‚
Cu(2) separation of 3.199(3) Å is more than twice the van
der Waals radius of Cu, viz., 2.80 Å2424,25 but less than that
(3.263(4) Å) observed in a sulfur-bridged dimer [Cu2(2-
SC5H4NH)2I2(p-tol3P)2],6b 7. The Cu(3)-S(1)-C(132) angle
of ca. 114° is similar to that observed in 7 (ca. 116°)6b or
[CuCl(PPh3)2(2-SC5H4NH)], 8, (ca. 113°),4a characteristic of
S-bonded 2-SC5H4NH with NH‚‚‚X hydrogen bonding.2-4
Terminal and bridging Cu-I bond distances, 2.700-2.740
Å, are less than the sum of radii of the Cu+ and I- (2.97
Å)24 but longer than the terminal Cu-I distances {2.603(2)
Å} observed in compound 7.6b The Cu- P bond distances,
2.238-2.282 Å, are comparable with that, 2.243(3) Å,
observed in 7. The Cu(3)-S(1) bond distance (2.359(6) Å)
is shorter than those observed in 7 (Cu-S, 2.393(4) and
2.425(4) Å)6b or 8 (Cu-S, 2.374(2) Å).4a Finally, the
C(132)-S(1) bond distance of 1.652(18) Å is comparable
to those in 7 (d(C-S), 1.690(12) Å)6b or 8 (d(C-S), 1.692(9)
Å).4a The NH‚‚‚I bond distance of 2.96 Å showed very weak
hydrogen bonding (sum of van der Waals radii, H‚‚‚I, 3.24
Å). The seven-memebered metallacyclic ring, formed by the
bridging dppe across the dinuclear Cu(µ-I)2Cu core, is
puckered with the longest C(1)-C(2) distance of 1.616(19)
Å.
Cu(3)-S(3)
Cu(3)-S(2)
S(2)-Cu(3)-Br(2)
Cu(3)-S(2)-Cu(2)* 71.67(2)
Cu(3)-Br(2)-Cu(2)* 71.559(19) S(2)-Cu(2)*-Br(2) 114.54(3)
Cu(1)-Br(1)-Cu(1)* 83.24(2)
Compound 5
2.3108(14) Cu(3)-I(3)
Br(1)-Cu(1)-Br(1)* 96.76(2)
Cu(1)-S(1)
Cu(1)-S(3)
Cu(1)-I(1)
Cu(2)-I(2)
Cu(3)-I(2)
2.6236(9)
2.6392(8)
2.2894(14)
2.3865(14)
2.3454(14)
110.95(4)
114.29(4)
101.0(4)
2.2998(14) Cu(1)-I(1)*
2.7133(9)
2.5913(8)
Cu(2)-S(1)
Cu(3)-S(3)
2.6587(10) Cu(3)-S(2)
Cu(3)-S(2)-Cu(2)* 73.19(4)
S(2)-Cu(3)-I(2)
S(2)-Cu(2)*-I(2)
I(1)-Cu(1)-I(1)*
Cu(3)-I(2)-Cu(2)*
Cu(1)-I(1)-Cu(1)*
67.98(2)
79.0(4)
iodide and three 2-SC5H4NH ligands are believed to combine
via bridging S donor atoms to form a boat-shaped six-
membered trinuclear Cu3S3I3 core of Cu3I3(2-SC5H4NH)3‚
CH3CN (A) species. Two six-membered trinuclear Cu3S3I3
cores combine in an inverse manner via four S-donor atoms
(µ3-S) to form the centrosymmetric hexanuclear central core,
Cu6S6I4(µ-I)2- (i.e., repeat unit B), which has four terminal
and two bridging iodine atoms in trans orientations. The
repeat unit (B) combines to another repeat unit via bridging
iodine atoms, and this process finally formed the infinite
linear chain polymer 2. The bond parameters of CH3CN
molecules essentially indicate the nonbonded nature. The
presence of CH3CN molecules between chains appears
essential to form the crystals in the presence of diphosphanes.
In the hexameric unit Cu6S6I4(µ-I)2, each of Cu(1), Cu(1)*,
Cu(2), and Cu(2)* atoms are bonded to three S atoms and
one I atom (CuS3I cores), while each of the Cu(3) and Cu(3)*
atoms are bonded to two S atoms and two I atoms (CuS2I2
cores). The iodine atoms bonded to Cu(2) and Cu(2)* bridge
the two adjacent hexameric units on both sides of the central
unit, and likewise two iodine atoms from adjacent hexameric
units bridge the central unit. This leads to the formation of
two eight-membered puckered metallacyclic rings of Cu4I2S2
core, on both sides of the central unit. Four sulfur atoms
Structures of Linear Polymers 2, 4, and 5. The atomic
numbering scheme of polymer 2 is shown in Figure 2a, while
Figure 2b shows a linear view of the polymer. Three Cu(I)
(23) Gottlieb, H. E.; Kotlyar, V.; Nudelman, A. J. Org. Chem. 1997, 62,
7512.
(24) Inorganic Chemistry: Principles of Structure and ReactiVity, 4th ed.;
Huheey, J. E., Keiter, E. A., Keiter, R. L., Eds.; Harper Collins College
Publishers: New York, 1993.
(25) Lobana, T. S.; Mahajan, R.; Castineiras, A. Trans. Met. Chem. 2001,
26, 440.
1918 Inorganic Chemistry, Vol. 44, No. 6, 2005

Versatility of Heterocyclic Thioamides
Figure 2. (a) Hexanuclear repeat unit B of polymer 2. (b) Linear chain of polymer 2 along a axis (pyridyls omitted for clarity).
(S(1), S(1)*, S(2), S(2)*) act as µ3-S donor atoms, and the
other two S atoms (S(3) and S(3)*) act as µ2-S donor atoms.
The geometry around each Cu center is distorted tetrahedral,
and the angles around Cu vary over a wide range, ca. 98-
123°. The variation of bond angles around S is more
widespread, ca. 76-125° in view of the large angular
flexibility at the S donor atom. The Cu-S-C bond angles
are typical of S-bonded neutral SC5H4NH.2 The Cu‚‚‚Cu
bond distance is 3.027(1) Å in the four-membered rings of
Cu(µ-S)2Cu cores, which is close to similar distance (2.795-
3.160 Å) observed in Cu6(2-SC5H4N)6.8b The angles at Cu
and S atoms of the four-membered rings are ca. 103 and
76.5°, which are typical of S-bridged dinuclear complexes
containing such rings.6
The CuS3I cores have two short and one long Cu-S bond
distances, while in the CuS2I2 cores, both Cu-S distances
Inorganic Chemistry, Vol. 44, No. 6, 2005 1919

Lobana et al.
Figure 3. Structure of polymer 4 showing the numbering scheme and 50% displacement ellipsoids. Hydrogen atoms have been omitted for clarity.
are similar to the shorter Cu-S distances of CuS3I core
(Table 2). All these Cu-S bond distances are shorter than
the sum of radii of Cu+ and S2- (2.61 Å: Cu+, 0.91 Å; S2-,
Cu(µ2-S)2Cu moiety. The corresponding Cu‚‚‚Cu distances
in 5 are 2.9356(11) Å in hetero-bridged Cu(µ2-I)(µ2-S)Cu
moiety and 2.7292(14) Å in homo-bridged Cu(µ2-S)2Cu
moiety. The Cu-S distances of the Cu(µ2-S)2Cu core are
unequal (4: Cu(2)-S(2), 2. 3213(9), Cu(2)-S(2)*, 2.5663(9)
Å; 5, Cu(2)-S(2), 2. 3457(14), Cu(2)-S(2)*, 2.5695(15) Å),
and four-membered rings form parallelograms (S-Cu-S:
67.85(3) 4, 67.28(4)° 5; Cu-S-Cu: 112.15(3)°, 4, 112.72(4)°
5) (Table 2). There is remarkable similarity of two Cu(µ2-
S)2Cu moieties in two polymers. In the hetero-bridged Cu(µ2-
X)(µ2-S)Cu moieties, since the Cu-X and Cu-S distances
are unequal, the four-membered rings do not form paral-
lelograms. Further, the S-Cu-X, Cu-X-Cu, and Cu-S-
Cu angles of hetero-bridged Cu(µ2-X)(µ2-S)Cu moieties lie
in the ranges, ca. 109-114, 67-71, and 71-73°, respectively
(Table 2). The Cu(µ2-X)2Cu cores also form parallelograms
with Cu-X-Cu and X-Cu-X bond angles of ca. 79-83
and 96-101°, respectively. It may be noted that the angles
at Cu, S, or X atoms of the various dimeric cores discussed
above are similar to the theoretically predicted values6 of
ca. 70 and 105°. Finally, in the six-membered rings formed
by Cu3S3 cores, the angles at S(1), S(2), and S(3) lie in the
range ca. 116-129° in both the polymers 4 and 5 (Table 2);
while the angles at Cu(1), Cu(2), and Cu(3) lie in the range
97-115°. However, the angles at S(1) and Cu(1) atoms are
the largest. The C-S bond distances, 1.699-1.733 Å, reveal
considerable double bond character.2
8b
1.70 Å}19 but somewhat longer than in Cu6(2-SC5H4N)6
with anionic ligands. The terminal Cu-I bond distances of
the Cu6S6I6 core lie in the close range, 2.578-2.593 Å (Table
2), which are close to the terminal Cu-I (2.603 Å) bond
distance in 7.6b Two iodines of Cu6S6I6 core involved in
bridging the adjacent hexameric units form longer bonds
(Cu(3)-I(3), 2.909(1) Å). All these Cu-I bond distances
are less than the sum of radii of Cu+ and I- (2.97 Å).19 The
C-S bond distances, 1.728-1.737 Å, reveal considerable
double-bond character,2 (cf. d(C-S) ) 1.764 Å) in Cu6(2-
SC5H4N)6}.8b
The polymeric complexes 4 and 5 are isostructural, and
the same numbering has been used for both; a depiction of
4 is given in Figure 3. The formation of polymers 4 and 5
is believed to take place via six-membered trinuclear Cu3S3X3
cores of Cu3X3(µ2-SC3H6N2)3 species C having three
bridging S atoms and three terminal X atoms. Two units of
species C interacted via two S and two X groups, in side-on
fashion unlike inverse fashion as in 2, forming the repeat
unit Cu6(µ3-SC3H6N2)2(µ2-SC3H6N2)4X2(µ2-X)4 (D). Two
halide ligands of repeat unit D interact with other repeat units
forming the infinite polymers 4 and 5. The repeat unit,
Cu6(µ3-SC3H6N2)2(µ2-SC3H6N2)4X2(µ2-X)4 (D), comprises
two components: steplike tetranuclear Cu4S2X2 cores involv-
ing two µ3-S and two µ2-X bridges and a dinuclear Cu2X2
core. Each of Cu(2) and Cu(2)* atoms are bonded to three
S and one X atoms; each of Cu(3) and Cu(3)′ atoms, as well
as Cu(1) and Cu(1)′ atoms are bonded to two sulfur atoms
and two halogen atoms. In the repeat unit, D, only two
halogen atoms are terminally bonded: the ones bonded to
Cu(3) and Cu(3)′ atoms.
Spectroscopy. The IR spectrum of 2-SC5H4NH shows the
υ(N-H) at 3190 (w) cm-1, which shifted to 3165 cm-1 in
compound 1 and to 3235 (w) cm-1 in compound 2. The ν(C-
S) peak at 1138 cm-1 of the free 2-SC5H4NH shifted to 1133
cm-1 in compound 1 and for dppe a characteristic ν(P-CPh)
peak at 1097s cm-1 in the complex confirmed its presence.
For compound 2, the shift of the diagnostic υ(C-S) peak
from 1135 (s) cm-1 to a split band at 1130 (s), 1115 (sh)
cm-1, took place. The ν(C-N) peak of CH3CN could not
be located, and the possibility is that it evaporated during
The steplike tetranuclear Cu4S2Br2 core of 4 has a Cu‚‚‚Cu
bond distance of 2.8826(7) Å, in hetero-bridged Cu(µ2-Br)-
(µ2-S)Cu moiety, and it is 2.7356(9) Å in homo-bridged
1920 Inorganic Chemistry, Vol. 44, No. 6, 2005

Versatility of Heterocyclic Thioamides
pellet formation in KBr. For 4 and 5, some characteristic
bands due to υ(N-H) and υ(C-S) were observed (cf.
Experimental Section).
polymer 2 (15%). The addition of CHCl3 to the reaction
mixture (CH3CN:CHCl3, 1:2 v/v) increased amount of 2
(45%) vis-a`-vis dimer (45%). Though CH3CN intercalates
between polymer chains and is necessary for polymer
formation, the ligand dppb is more soluble in CHCl3 and
thus solvates it more extensively leaving behind CuI and
SC5H4NH to polymerize. In the absence of CHCl3, dppb
preferentially binds CuI and forms a dimer first and a lower
amount of 2 results. The dppp is relatively more soluble in
CH3CN and thus 2 (45%) and 3b (45%) were formed in equal
quantity; however, the addition of CHCl3 (CH3CN:CHCl3,
1:2 v/v) enhanced the yields, 2 (75%) and 3b (15%). In the
case of dppm and dppen, due to their higher solubility in
CH3CN, the polymer 2 in 50-55% and dimers 3c and 3d in
40-50% yields were isolated either in CH3CN alone or in
the solvent mixture (CH3CN:CHCl3, 1:2 v/v). Finally, in the
case of dppp and dppb ligands, dimers 3a and 3b were
formed first and from filtrate polymer 2 was isolated, while
in case of dppm and cis-dppen ligands, polymer 2 was
formed first and dimers 3c and 3d formed later from the
mother liquor.
1
The H NMR spectrum of 1 in CDCl3 (poorly soluble)
showed peaks due to -CH2- protons of alkane moiety of
dppe at δ 2.62 ppm. The pyridyl and phenyl protons showed
multiplets in the region, δ 6.62 to 7.62 ppm; the NH proton
signal was too broad to be detected. The proton NMR
spectrum of the partially soluble compound 2 in CDCl3
showed a NH proton signal at 13.20 ppm vs free ligand signal
at 13.40.6b The presence of methyl signal of CH3CN was
shown at 2.01 ppm, a region characteristic of the free
CH3CN.18 Pyridyl H(3), H(4), and H(5) protons shifted to
high field and were broad peaks due to two types of
2-SC5H4NH ligands in compound 2 (cf. Experimental
Section). Interestingly, H(6) protons did not merge, and two
broad singlets at 7.56 and 7.47 ppm were clearly visible.
The proton NMR spectrum of compound 4 in CDCl3 and of
5 in CD3CN showed the bands due to CH2 and NH protons
at low field vis-a`-vis free ligand as listed in Experimental
Section.
The formation of unusual triangular cluster 1 and linear
polymer 2 in the presence of diphosphanes in CH3CN-
CHCl3 medium and also of 4 and 5 in the presence of
CH3CN-CHCl3 is significant, and it demonstrates the role
of diphosphanes (2) and solvents such as chloroform (4 and
5) in the construction of novel polymers.
Conclusion
In summary, copper(I) iodide and pyridine-2-thione in the
presence of diphosphanes formed unusual cluster 1 and linear
polymer 2, which has acetonitrile between its chains. The
dimeric complexes, [Cu2(µ2-I)2(diphosphanes)2] 3a-d, were
also isolated during the formation of 2. Unlike pyridine-2-
thione, the ligands 1,3-imidazolidine-2-thione and pyrimi-
dine-2-thione did not form polymers similar to 2 in the
presence of diphosphanes; rather only dimers (Cu2(µ2-I)2-
(diphosphanes)2) 3a-d were formed. However, 1,3-imid-
azolidine-2-thione and copper(I) iodide and bromide have
formed unusual linear polymers 4 and 5, but no such polymer
was formed by pyrimidine-2-thione. Dimers involve iodide
bridging with chelating diphosphanes, as verified by X-ray
crystallography for (Cu2(µ2-I)2(dppp)2).7b
Acknowledgment. Sharma, Sharma, and Mehra thank the
Guru Nanak Dev University for research facilities. Financial
support from CSIR, New Delhi, is gratefully acknowledged.
We thank reviewers for useful suggestions and for healthy
refereeing.
Supporting Information Available: X-ray crystal data in CIF
format (CCDC numbers are 190225, 208445, 225476, and 225477).
This material is available free of charge via the Internet at http://
pubs.acs.org.
In the formation of 2, the use of CH3CN alone gave a
higher amount of 3a dimer (80%) and low amount of
IC0484809
Inorganic Chemistry, Vol. 44, No. 6, 2005 1921