Chemistry of thiocarboxylates: Syntheses and characterization of silver and copper thiocarboxylate complexes, and the structures of [Ph4P][M(SC{O}Me)2] (M = Cu or Ag) and [Et3NH][Ag(SC{O}Ph)2]

Article abstract of DOI:10.1039/a904718b

The bis(thiocarboxylate) complexes of silver(i) and copper(i) namely, [Ph₄P][M(SC{O}Me)₂], (M = Cu 1 or Ag 2) and [Et₃NH][M(SC{O}Ph)₂] (M = Cu 3 or Ag 4) were prepared from the appropriate metal salt, RC{O}S^- anions and the counter ion in the ratio 1:2:1. The structures of 1, 2 and 4 were determined by X-ray crystallography. The compounds 1 and 2 are isomorphous and isostructural. In both structures, the metal is bonded to sulfur atoms of two thioacetate ligands to give a near-linear geometry. A crystallographically imposed 2-fold rotational symmetry is present in the anions and the cations. The [Ag(SC{O}Ph)₂]^- anion in 4 also has an approximately-linear SAgS skeleton. One of the S atom interacts weakly with a second silver(I) ion to form a dimer. The N-H hydrogen atom of the Et₃NH⁺ cation is involved in N-H ... O hydrogen bonding to a carbonyl oxygen atom of the anion. There is a crystallographic center of symmetry present in this 'ion-pair dimer', having a rectangular arrangement of Ag₂S₂ with a T-shaped coordination geometry around the silver atoms. All the compounds decompose under a nitrogen atmosphere to the corresponding metal sulfides according to weight loss observed in TG. The Royal Society of Chemistry 1999.

Full text of DOI:10.1039/a904718b

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Chemistry of thiocarboxylates: syntheses and characterization of
silver and copper thiocarboxylate complexes, and the structures of
[Ph4P][M(SC{O}Me)2] (M ؍ Cu or Ag) and
[Et3NH][Ag(SC{O}Ph)2]
Jeyagowry T. Sampanthar,a Jagadese J. Vittal*a and Philip A. W. Dean*b
a Department of Chemistry, National University of Singapore, Kent Ridge, Singapore 119260.
E-mail: chmjjv@nus.edu.sg
b Department of Chemistry, The University of Western Ontario, London, Ontario,
Canada N6A 5B7. E-mail: pawdean@julian.uwo.ca
Received 14th June 1999, Accepted 21st July 1999
The bis(thiocarboxylate) complexes of silver() and copper() namely, [Ph4P][M(SC{O}Me)2], (M = Cu 1 or Ag 2)
and [Et3NH][M(SC{O}Ph)2] (M = Cu 3 or Ag 4) were prepared from the appropriate metal salt, RC{O}SϪ anions
and the counter ion in the ratio 1:2:1. The structures of 1, 2 and 4 were determined by X-ray crystallography. The
compounds 1 and 2 are isomorphous and isostructural. In both structures, the metal is bonded to sulfur atoms of
two thioacetate ligands to give a near-linear geometry. A crystallographically imposed 2-fold rotational symmetry
is present in the anions and the cations. The [Ag(SC{O}Ph)2]Ϫ anion in 4 also has an approximately-linear SAgS
skeleton. One of the S atom interacts weakly with a second silver() ion to form a dimer. The N–H hydrogen atom
of the Et3NHϩ cation is involved in N–H ؒ ؒ ؒ O hydrogen bonding to a carbonyl oxygen atom of the anion. There is
a crystallographic center of symmetry present in this ‘ion-pair dimer’, having a rectangular arrangement of Ag2S2
with a T-shaped coordination geometry around the silver atoms. All the compounds decompose under a nitrogen
atmosphere to the corresponding metal sulfides according to weight loss observed in TG.
In this paper we report the synthesis and characterization
Introduction
of bis(thiocarboxylate) complexes of silver() and copper()
namely [Ph4P][M(SC{O}Me)2], (M = Cu 1 or Ag 2) and
[Et3NH][M(SC{O}Ph)2] (M = Cu 3 or Ag 4), and the struc-
tures of 1, 2 and 4 as determined by single crystal X-ray dif-
fraction techniques. The thermal decomposition of these
compounds under a nitrogen atmosphere followed by TG is
described.
Thiocarboxylates are an interesting class of ligands with a soft
sulfur donor site and a hard oxygen donor site. These ligands
are expected to exhibit a variety of interesting bonding modes,1
as found for the related monothiocarbamates and xanthates.
However, the chemistry of metal–thiocarboxylates has not been
studied in detail.2 We have been interested in the chemistry of
the thiobenzoate anion.3–12 In most† [M(SC{O}Ph)3]Ϫ anions
of the Group 12 elements, the metal atoms are surrounded by
three sulfur atoms in a trigonal planar fashion.3 This unusual
geometry is otherwise exhibited only in complexes of bulky thio-
late ligands.13 In the structure of the [Na{Cd(SC{O}Ph)3}2]Ϫ
anion, the PhC{O}SϪ ligand binds to the soft Cd via S, to give a
CdS3 kernel of trigonal planar geometry.4 (The hard Na binds
to the ligands via O to give an NaO6 kernel.) Recently, we have
reported10 homoleptic anionic transition metal complexes of
the type [Ph4P][M(SC{O}Ph)3] (M = Mn, Co or Ni) where both
oxygen and sulfur atoms are bonded to the central metal atom
in a bidentate fashion. Although structural data for several
other thiobenzoate complexes of main-group and transition
elements are available in the literature,14–21 there has been no
systematic study. To our knowledge no homoleptic thiocarb-
oxylate complexes of coinage metals have been reported. How-
ever, structural data have been given22 for a dinuclear Cu()
thiobenzoate triphenylphosphine complex and the simple
neutral metal–thiobenzoates of Ag and Cu are known.23
Experimental
All the materials used in the syntheses were obtained com-
mercially and used as received. Thioacetic acid (97%), thio-
benzoic acid (95%) and triethylamine were purchased from
Fluka. The solvents were dried over 3 Å molecular sieves and
degassed with N2 prior to use. All the preparations were carried
out under a N2 atmosphere. The microanalytical laboratory
at NUS performed the microanalysis. For the NMR spectra,
recorded on a AC 300 MHz spectrometer, solutions were pre-
pared in CDCl3 and external SiMe4 was used as the reference.
Thermogravimetric analyses under N2(g) were carried out using
an SDT 2980 TGA thermal analyser with a heating rate of
20 ЊC minϪ1 and a sample size of about 5–10 mg per run. Solu-
tion IR spectra were obtained using a Bio-Rad FTIR spec-
trometer using a cell of path length 0.1 mm, with KBr windows.
Syntheses
Apart from exhibiting interesting bonding modes, thiocarb-
oxylates are also used to synthesize ‘single-source’ precursors
for metal sulfide materials. Hampden-Smith and co-workers24,25
have successfully used a variety of metal thiocarboxylates as
precursors to prepare metal sulfides that include ZnS and CdS.
[Ph4P][Cu(SC{O}Me)2] 1. Et3NHϩMeC{O}SϪ was obtained
in situ as a pale yellow solution from thioacetic acid (0.5 mL,
7.0 mmol) and an aqueous solution (15 mL) containing
triethylamine (1.0 mL, 7.2 mmol). To this, a solution of CuCl
(0.32 g, 3.2 mmol) in CH3CN (15 mL) was added slowly with
stirring, causing a color change to yellowish red. A solution of
Ph4PCl (1.32 g, 3.5 mmol) in H2O (10 mL) was added and the
† Planar and pyramidal CdS3 kernels are found in rhombohedral
[Ph4P][Cd(SC{O}Ph)3].11
J. Chem. Soc., Dalton Trans., 1999, 3153–3156
This journal is © The Royal Society of Chemistry 1999
3153

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Table 1 Crystal data and experimental details for 1, 2 and 4
1
2
4
Chemical formula
Formula weight
T/K
Crystal system
Space group
a/Å
C28H26CuO2PS2
553.12
293(2)
Tetragonal
P421c (no. 114)
11.5184(6)
11.5184(6)
19.767(2)
C28H26AgO2PS2
597.45
293(2)
Tetragonal
P421c (no. 114)
11.7596(1)
11.7596(1)
19.1859(3)
C20H26AgNO2S2
484.41
295(2)
Monoclinic
P21/c
11.1129(2)
19.9831(4)
10.7747(1)
114.225(1)
2182.04(6)
4
b/Å
c/Å
β/Њ
V/Å3
2622.5(3)
4
1.401
2653.18(5)
4
1.496
Z
Dc/g cmϪ3
1.475
Reflections measured
Independent reflections
µ/mmϪ1
Data/restraints/parameters
GooF on |F|2
Final R indices
R indices (all data)
11975
2321 (Rint = 0.1320)
1.076
1389/0/155
1.195
R1 = 0.1072, wR2 = 0.1439
R1 = 0.1796, wR2 = 0.1654
16269
3420 (Rint = 0.0224)
1.001
2780/0/156
1.061
R1 = 0.0332, wR2 = 0.0799
R1 = 0.0455, wR2 = 0.0851
13365
5326 (Rint = 0.0308)
1.128
3320/9/236
1.023
R1 = 0.0466, wR2 = 0.0922
R1 = 0.0910, wR2 = 0.1190
solvents were removed from the reaction mixture under reduced
pressure to give a reddish oily product. This was dissolved in
CH2Cl2 (10 mL), H2O (15 mL) was added and the mixture was
stirred for 5 min. The CH2Cl2 layer was separated and concen-
trated to ca. 5 mL. Hexane (5 mL) and Et2O (30 mL) were
added, and the mixture was left undisturbed at 0 ЊC to obtain a
reddish yellow precipitate along with red crystals. The crystals
were separated, washed with Et2O, and dried in a desiccator
under vacuum. Yield: 1.18 g (66%). Calc. for C28H26CuO2PS2:
and the mixture was left undisturbed at 0 ЊC. A reddish yellow
solid was obtained in a day. This was separated by decantation,
washed with Et2O and dried under vacuum. Yield: 1.84 g (77%).
Satisfactory elemental analysis could not be obtained. How-
ever, the 1H and 13C NMR spectra and TG are consistent with
the proposed formula, C H CuO NS . ν(C᎐O) 1636, 1603
᎐
20 26
2
2
cmϪ1. NMR data: δ(1H) 1.37 (t, 9H, CH3), 3.29 (q, 6H, CH2),
7.34–7.43 (dt, 6H, m- and p-H of Ph), 8.16 (d, 4H, o-H of Ph).
δ(13C) 9.49 (CH3), 46.93 (CH2), 128.43 (C2(or 3) of Ph), 129.17
(C3(or 2) of Ph), 132.32 (C4 of Ph), 141.61 (C1 of Ph), 208.24
(CO).
C, 60.80; H, 4.70. Found: C, 60.20; H, 5.34%. ν(C᎐O)
᎐
1616 cmϪ1. NMR data: δ(1H) 2.49 (s, 6H, CH3), 7.5–7.8 (m,
1
20 H, Ph); δ(13C) 39.52 (CH3), 117.22 (C1 of Ph, J(P–C) = 89
3
Hz), 131.39 (C3,5 of Ph, J(P–C) = 13 Hz), 134.98 (C2,6 of Ph,
[Et3NH][Ag(SC{O}Ph)2] 4. Thiobenzoic acid (1.0 mL, 8.5
mmol) was added dropwise to a CHCl3 solution (5 mL) con-
taining triethylamine (1.2 mL, 8.6 mmol). A solution of AgNO3
(0.69 g, 4.1 mmol) in H2O (15 mL) was added to give a cream
colored turbid mixture, which was stirred for 15 min. The
yellow CHCl3 layer was separated, MeOH (2–3 mL) and Et2O
(15–20 mL) were added, and the mixture was left to crystallize
at 0 ЊC. The creamy white crystals were decanted off, washed
with Et2O and dried in vacuum. Yield: 1.55 g (79%). Calc. for
C20H26AgO2NS2: C, 49.59; H, 5.37; N, 2.89. Found: C, 49.50; H,
5.16; N, 2.90%. NMR data: δ(1H) 1.38 (t, 9H, CH3), 3.30 (q,
6H, CH2), 7.32–7.44 (dt, 6H, m- and p-H of Ph), 8.15 (d, 4H,
o-H of Ph); δ(13C) 9.65 (CH3), 47.33 (CH2), 128.38 (C2(or 3) of
Ph),129.09 (C3(or 2) of Ph), 132.06 (C4 of Ph), 142.63 (C1 of Ph),
208.13 (CO).
4
2J(P–C) = 10 Hz), 136.42 (C4 of Ph, J(P–C) = 3 Hz), 209.54
(CO).
[Ph4P][Ag(SC{O}Me)2] 2. Thioacetic acid (1.0 mL, 14.0
mmol) was added slowly to an aqueous solution (25 mL)
containing triethylamine (2.0 mL, 14.4 mmol) to obtain a pale
yellow solution of Et3NHϩCH3C{O}SϪ. To this, a solution of
AgNO3 (1.16 g, 6.8 mmol) in H2O (15 mL) was added with
continuous stirring, to give a cream colored solution. A solu-
tion of Ph4PCl (2.55 g, 6.8 mmol) in H2O (10 mL) was added to
this reaction mixture with stirring to give a cream colored pre-
cipitate. Dichloromethane (10 mL) was added to the reaction
mixture and the whole stirred for 5 min, at which point the
CH2Cl2 layer was yellow. The organic layer was separated and
concentrated to a volume of ca. 5 mL, then Et2O was layered on
the concentrate and the mixture was left undisturbed at 0 ЊC to
obtain cream crystals. The crystals were decanted off, washed
with Et2O and dried under vacuum. Yield: 2.2 g (54%). Calc. for
C28H26AgO2PS2: C, 56.29; H, 4.35. Found: C, 56.63; H, 4.27%.
Crystal structure determinations
The diffraction experiments were carried out on a Bruker AXS
SMART CCD 3-circle diffractometer with a Mo-Kα sealed
tube at 23 ЊC. The software used was: SMART26 for collecting
frames of data, indexing reflections and determination of
lattice parameters; SAINT26 for integration of intensity of
reflections and scaling; SADABS27 for empirical absorption
correction; and SHELXTL28 for space group determination,
structure solution and least-squares refinements on F 2. The
single crystals were obtained during the syntheses. The crystals
were mounted at the ends of glass fibres and used for diffraction
experiments. The crystal data and experimental details are
given in Table 1. Poor agreement factors for 1 may be attributed
to the weakly diffracting nature of the crystals. The absolute
structure parameters were refined to Ϫ0.02(7) and 0.02(4) for
1 and 2 respectively.
ν(C᎐O) 1610 cmϪ1. NMR data: δ(1H) 2.39 (s, 6H, CH3),
᎐
7.74–7.92 (m, 20H, Ph); δ(13C) 38.36 (CH3), 118.12 (C1 of Ph,
3
1J(P–C) = 89 Hz), 131.42 (C3,5 of Ph, J(P–C) = 13 Hz), 135.07
(C2,6 of Ph, 2J(P–C) = 10 Hz), 136.46 (C4 of Ph, 4J(P–C) =
3 Hz), 209.97 (CO).
[Et3NH][Cu(SC{O}Ph)2] 3. Thiobenzoic acid (1 mL, 8.5
mmol) was added dropwise with stirring to a solution of tri-
ethylamine (1.2 mL, 8.6 mmol) in CHCl3 (5 mL). The resultant
solution of Et3NHϩPhC{O}SϪ was added to CuCl (0.42 g, 4.2
mmol) in CH3CN (15 mL) to get a reddish yellow mixture. The
mixture was stirred for 15 min., then the solvent was removed
under reduced pressure to leave a red viscous oil. The oil was
dissolved in CHCl3 (5 mL) and washed with H2O (ca. 30 mL) to
remove Et3NHCl. The organic layer was separated, layered with
hexane (5–8 mL) and Et2O (30–40 mL) until it became turbid,
CCDC reference number 186/1589.
See http://www.rsc.org/suppdata/dt/1999/3153/ for crystallo-
graphic files in .cif format.
3154
J. Chem. Soc., Dalton Trans., 1999, 3153–3156

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Table 2 Selected bond distances (Å) and angles (Њ) for the anions in 1
and 2
1
2
M(1)–S(1)
S(1)–C(1)
O(1)–C(1)
C(1)–C(2)
2.151(3)
2.359(1)
1.730(4)
1.999(4)
1.499(5)
1.716(12)
1.210(12)
1.494(14)
S(1)–M(1)–S(1A)
C(1)–S(1)–M(1)
O(1)–C(1)–C(2)
O(1)–C(1)–S(1)
C(2)–C(1)–S(1)
176.6(2)
100.2(4)
122.7(11)
124.5(9)
112.8(9)
178.96(5)
98.99(12)
120.9(3)
124.4(3)
114.8(3)
Symmetry operator: A Ϫx ϩ 1, Ϫy, z.
Fig. 1 A perspective view of the molecule, 2. The non-hydrogen atoms
are drawn as 50% probability thermal ellipsoids.
Results and discussion
Preparation of [Ph4P][M(SC{O}CH3)2] and [Et3NH][M(SC{O}-
Ph)2] (M ؍ Ag or Cu)
The complexes 1–4 were prepared by reacting suitable metal
salts with two equivalents of the appropriate deprotonated thio-
carboxylic acid [eqn. (1)]. For thiobenzoate complexes, the
2[Et3NH][SC{O}R] ϩ MX →
[Et3NH][M(SC{O}R)2] ϩ Et3NHX (1)
triethylamine base served to remove the proton from PhC-
{O}SH and the resultant Et3NHϩ cation was used as the coun-
ter ion to isolate the product in the solid state. The Et3NHϩ salts
of the thioacetate complexes were found to be moisture sensi-
tive, very unstable in air and the yellow color changed to dark
brown even under nitrogen at 5 ЊC. However, the Ph4Pϩ cation
was successfully used to isolate the thioacetate complexes of Cu
and Ag as shown in eqn. (2).
Fig. 2 The structure of the ‘ion-pair dimer’ 4 in the solid state. The
thermal ellipsoids are shown at the 50% probability level.
[Cu(SR)2]Ϫ anions. Both of these have bulky R groups: SR =
2,3,5,6-tetramethylbenzenethiolate31 and adamantylthiolate.32
(We have noted earlier that PhC{O}SϪ mimics bulky thiolates
as a ligand.3) The Cu–S distances observed in these two thiolate
complexes, 2.137 and 2.147 Å, are slightly lower than the value
observed in 1. The Cu ؒ ؒ ؒ O distance, 2.998 Å, indicates that
there is no interaction between the Cu and O atoms (sum of the
van der Waals radii,33 2.9 Å). The atoms Cu(1), S(1), O(1), C(1)
and C(2) are in a plane (deviation, 0.01 Å) and the interplanar
angle between the two thioacetates is 76.6(3)Њ.
The Ag–S distance and S–Ag–S angle in the anion of 2
are 2.359(1) Å and 178.96(5)Њ respectively. The CSD search
revealed no mononuclear two-coordinate silver() thiolate com-
plexes. In all the 12 hits, linear AgS2 fragments were present in
polynuclear silver thiolate anions. Thus, to the best of our
knowledge, 2 is the first example of a structurally characterized
mononuclear Ag complex having a linear S–Ag–S geometry.‡
The Ag–S distances found in 2 are comparable to those
reported in the literature (range, 2.289–2.528 Å). There appears
to be no interaction between the Ag and the carbonyl oxygen
atoms of the thioacetate ligands (Ag(1) ؒ ؒ ؒ O(1) and the sum of
the van der Waals radii of Ag and O are 3.082 and 2.9 Å
respectively). All the non-hydrogen atoms in the thioacetate
ligand and Ag(1) are in a plane (deviation, 0.006 Å) and the
inter-planar angle between the two such planes, is 71.8(1)Њ.
The structure of 4 is shown in Fig. 2, and selected bond
distances and angles are given in Table 3. In the complex anion,
Ag(1) is bonded to two thiobenzoate anions to give an
approximately linear S–Ag–S coordination geometry. The Ag–S
distances are 2.359(1) and 2.382(1) Å. The S–Ag–S angle,
161.16(4)Њ, is smaller than S–M–S observed in 1 and 2. The
Ag(1)–S(2) distance is longer than Ag(1)–S(1). The phenyl rings
in the two PhC{O}SϪ ligands are twisted from the C–C{O}S
plane by 12.1(2) and 22.0(1)Њ. The interplanar angle between
[Et3NH][M(SC{O}Me)2] ϩ Ph4PCl →
[Ph4P][M(SC{O}Me)2] ϩ Et3NHX (2)
The isolated yield of these compounds varies from 54 to 79%.
1
The compounds were characterized by elemental analysis, H
and 13C NMR spectra in solution and IR spectra and are con-
sistent with the empirical formula. The crystal structures of the
compounds were determined by single crystal X-ray diffraction
techniques.
Molecular structures
The compounds 1 and 2 are isomorphous and isostructural.
The anions and the cations are well separated in the two struc-
tures. The structure of the Ph4Pϩ cation is unexceptional and
will not be discussed further. In the [M(SC{O}Me)2]Ϫ anion,
the central metal atom is coordinated to the sulfur atoms of the
thioacetates to give a two-coordinate near-linear geometry. The
anion has a crystallographically imposed 2-fold symmetry. A
representative view of the anion in 2 is shown in Fig. 1. Selected
bond distances and angles for the anions in 1 and 2 are summar-
ized in Table 2. In the anion of 1, the Cu-S distance and S–Cu–
S angle are 2.151(3) Å and 176.6(2)Њ respectively. A search in the
Cambridge Structural Database (CSD) System29 revealed there
are only 9 compounds containing two-coordinate Cu() as CuS2
fragments.‡ Of those, only two contain discrete monomeric
Ϫ
‡ The anions MS2 (M = Cu, Ag) are known in the gas phase, and are
thought to be linear.30
J. Chem. Soc., Dalton Trans., 1999, 3153–3156
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Table 3 Selected bond distances (Å) and angles (Њ) for the anion in 4
References
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S(1)–C(1)
S(2)–C(8)
2.359(1)
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1.727(4)
1.729(3)
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1.213(4)
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1.512(4)
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161.16(4)
106.8(1)
107.2(1)
119.6(3)
123.5(3)
C(2)–C(1)–S(1)
O(2)–C(8)–C(9) 119.8(3)
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116.9(2)
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2
3
4
150–460
180–460
100–280
110–340
16.3
21.7
17.7
25.6
14.4
20.7
18.1
25.6
a Calculated for the formation of the corresponding metal sulfide, M2S.
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the planes containing S(1), O(1), C(1), C(2) (deviation, 0.00 Å)
and S(2), O(2), C(8), C(9) (deviation, 0.06 Å) is 57.8(1)Њ. This
value is much smaller than the corresponding ones observed in
1 or 2. These differences may be explained if we consider the
secondary interactions of [Ag(SC{O}Ph2]Ϫ in the crystal lattice.
The carbonyl oxygen atoms of the PhC{O}SϪ ions are
involved in hydrogen bonding. The N–H hydrogen atom is
strongly hydrogen bonded to O(2). The relevant parameters are:
H(1) ؒ ؒ ؒ O(2), 1.887(4) Å, N(1) ؒ ؒ ؒ .O(2), 2.776(4) Å, N–H ؒ ؒ ؒ
O, 165.0(1)Њ. This N–H ؒ ؒ ؒ O᎐C hydrogen bonding appears to
᎐
21 N. Mehmet and D. A. Tocher, Inorg. Chim. Acta, 1991, 188, 71.
22 G. Speier, V. Fulop and G. Argay, Transition Met. Chem., 1991, 16,
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23 V. V. Savant, J. Gopalakrishnan and C. C. Patel, Inorg. Chem., 1970,
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25 M. D. Nyman, M. J. Hampden-Smith and E. N. Duesler, Chem.
Vap. Deposition, 1996, 2, 171.
26 SMART and SAINT Software Reference Manuals, Version 4.0,
Siemens Energy & Automation, Inc., Analytical Instrumentation,
Madison, WI, 1996.
27 G. M. Sheldrick, SADABS, a software for empirical absorption
correction, University of Göttingen, 1996.
28 SHELXTL Reference Manual, Version 5.03, Siemens Energy &
Automation, Inc., Analytical Instrumentation, Madison, WI, 1996.
29 F. H. Allen, J. E. Davies, J. J. Galloy, O. Johnson, O. Kennard,
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weaken the C(8)–O(2) bond (1.232(4) Å) as compared to C(1)–
O(1). Also found is a very weak interaction between H(19) and
O(1). The relevant parameters are: H(19) ؒ ؒ ؒ O(1), 2.436(5) Å,
C(19) ؒ ؒ ؒ .O(1), 3.340(5) Å, C–H ؒ ؒ ؒ O, 155.0(1)Њ. Evidently the
anion and the cation are present as an ion-pair in the solid state.
There is also a weak intermolecular interaction between Ag(1)
and S(2A) atoms in the solid state. The Ag(1) ؒ ؒ ؒ S(2A) dis-
tance, 3.106 Å between adjacent [Ag(SC{O}Ph)2]Ϫ anions is less
than the sum of the van der Waals radii,33 3.50 Å. If we con-
sider this interaction, then the structure can be described as an
‘ion-pair dimer’ in the solid-state (Fig. 2) with T-shaped geom-
etry around the silver atoms. The presence of a crystallographic
centre of inversion results in this ‘ion-pair dimer’ having
rectangular geometry. Such ion-pairs exist in [Et3NH][Cd-
(SC{O}Ph)3]6 also.
Thermogravimetric analysis
Thermal decomposition of the compounds was studied by
thermogravimetry under an N2 atmosphere. All the complexes
decompose in multi-step processes. A summary of the overall
weight losses is displayed in Table 4. The residual weight at the
end of the decomposition indicated the formation of the
corresponding metal sulfides.
31 S. A. Koch, R. Fikar, M. Millar and T. O’Sullivan, Inorg. Chem.,
1984, 23, 122.
32 K. Fujisawa, S. Imai, N. Kitajima and Y. Moro-oka, Inorg. Chem.,
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33 A. Bondi, J. Chem. Phys., 1964, 68, 441.
Acknowledgements
J. J. V. would like to thank the National University of Singapore
for a research grant (Grant No. RP970618), and P. A. W. D.
thanks the Natural Sciences and Engineering Research Council
of Canada for financial support.
Paper 9/04718B
3156
J. Chem. Soc., Dalton Trans., 1999, 3153–3156