Synthesis and characterization of some triorgano, diorgano, monoorganotin and a triorganolead heteroaromatic dithiocarbamate complexes

Article abstract of DOI:10.1016/j.jorganchem.2011.11.015

The reactions of benzyl-thiophen-2-ylmethyldithiocarbamate and 4-methyl-benzyl-thiophen-2-ylmethyldithiocarbamate with six organotin compounds and one organolead compound resulted in seven dithiocarbamate complexes exhibiting different structural forms. The compounds have been characterized by multinuclear NMR and IR spectral studies. X-ray crystallographic study of the compounds were made to understand the structure and bonding in these molecules. The dithiocarbamate ligands in all the organotin and organolead complexes showed anisobidentate bonding mode, however, in case of dichlorotin bis(dithiocarbamate) symmetrically bidentate mode of bonding was observed. Representative compounds [Ph₃Sn{(C₆H₅)(CH ₂)}{(C₄H₃S)(CH₂)}NCS₂] 1 and [Ph₃Pb{(C₆H₅)(CH₂)} {(C ₄H₃S)(CH₂)}NCS₂] 7 on pyrolysis yielded corresponding sulfides, SnS and PbS showing the usefulness of these dithiocarbamate complexes as single source precursors for the preparation of metal sulfides.

Full text of DOI:10.1016/j.jorganchem.2011.11.015

Journal of Organometallic Chemistry 700 (2012) 69e77
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and characterization of some triorgano, diorgano, monoorganotin
and a triorganolead heteroaromatic dithiocarbamate complexes
*
Neetu Singh, Subrato Bhattacharya
Department of Chemistry, Banaras Hindu University, Varanasi 221005, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The reactions of benzyl-thiophen-2-ylmethyldithiocarbamate and 4-methyl-benzyl-thiophen-2-
ylmethyldithiocarbamate with six organotin compounds and one organolead compound resulted in
seven dithiocarbamate complexes exhibiting different structural forms. The compounds have been
characterized by multinuclear NMR and IR spectral studies. X-ray crystallographic study of the
compounds were made to understand the structure and bonding in these molecules. The dithiocarba-
mate ligands in all the organotin and organolead complexes showed anisobidentate bonding mode,
however, in case of dichlorotin bis(dithiocarbamate) symmetrically bidentate mode of bonding was
Received 17 August 2011
Received in revised form
2 November 2011
Accepted 15 November 2011
Keywords:
Organotin
Organolead
Dithiocarbamate
Crystal structure
NMR
observed. Representative compounds [Ph3Sn{(C6H5)(CH2)}{(C4H3S)(CH2)}NCS2]
1
and [Ph3Pb
{(C6H5)(CH2)} {(C4H3S)(CH2)}NCS2] 7 on pyrolysis yielded corresponding sulfides, SnS and PbS showing
the usefulness of these dithiocarbamate complexes as single source precursors for the preparation of
metal sulfides.
TGA
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
The work described in this paper covers the syntheses and
molecular structures of benzyl thiophene-2-ylmethyl-dithiocarba-
The chemistry of dithiocarbamates has grown with prolific speed
on account of multifaceted reasons. One of the important structural
consequences of dithio ligand is the preferential stabilization of
specific stereochemistry in their metal complexes. Dithio ligands are
considered as soft donors showing excellent coordination ability.
They form stable complexes with transition as well as non-transition
metal ions [1,2] and exhibit variety of coordination modes in homo
andheteronuclearcomplexesdependingonthebindingmodesofthe
ligands towards the metal centre [3e7]. Owing to their strong metal
binding capacity, dithio ligands act as inhibitors of enzymes and
significantly affect biological systems [8e10]. The dieth-
yldithiocarbamate anion, Et2CNSꢀ2 is extensively used as antidote for
copper poisoning, i.e., Wilson’s disease [11] and ameliorating neph-
rotoxicity associated with platinum-based chemotherapy [12]. In
addition to the medicinal uses, metal dithiocarboxylates are widely
used in the vulcanization of rubber [13], as pesticides [14] and as
synthetic precursors for the formation of SnS nanocrystals by their
solvothermal decomposition [4,15]. In the series of extensive appli-
cation of dithiocarbamates, a novel class of dithiocarbamate termi-
nated dendrimer and their use as ligand for the synthesis of
ruthenium complexes has been reported recently [16].
mate complexes of tetravalent tin and lead. The reason behind the
choice of this ligand is the presence of an extra sulfur donor atom
which can possibly be utilized for coordination with another metal
salt or organometallic fragment as shown in Scheme 1.
2. Experimental
2.1. Starting materials
All solvents were of reagent grade quality and purchased
commercially. These were purified by standard methods. For the
synthesis of ligands solvents were dried carefully prior to their use
[17]. All organotin chlorides and triphenyllead chloride (Sigmae
Aldrich) were used as received. Thiophene-2-carboxaldehyde
(SigmaeAldrich), triethylamine (Merck), benzyl amine (Merck) and
its methyl derivative were distilled before use.
2.2. Instrumentation
Elemental analyses were performed using an Exeter Model E-
440 CHN analyser. NMR spectra were obtained using a JEOL AL 300
FTNMR spectrometer. Infrared spectra were recorded from KBr
pellets on a Varian 3100 FT-IR spectrophotometer in the region
* Corresponding author. Tel.: þ91 542 6702451.
E-mail addresses: s_bhatt@bhu.ac.in, bhatt99@yahoo.com (S. Bhattacharya).
400e4000 cmꢀ1
.
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.11.015

70
N. Singh, S. Bhattacharya / Journal of Organometallic Chemistry 700 (2012) 69e77
13C NMR (CDCl3) (ppm): 8.60 (CH3), 45.77 (CH2), 49.66, 54.42
(AreCH2), 124.97e140.04 (5C, Ph; 4C, Thioph), 213.60 (C/S).
2.4.1.2. (B) MBthdtc. A similar procedure was followed to synthe-
sise MBthdtc, by using 4-methyl benzyl amine in place of benzyl-
amine. Yield- 93%. IR (KBr) (cmꢀ1) 1497
3061, 3315 n(CeH), 950 n
n
(C]N), 2831, 2919, 3025,
(C S). 1H NMR (CDCl3) (ppm): 2.28 (s, 3H,
CH3), 1.42e1.48 (t, 3H, CH3, JHeH ¼ 6.99 Hz), 3.29e3.35 (q, 2H, CH2,
JHeH ¼ 7.2 Hz), 5.46 (s, 2H, CH2), 5.52 (s, 2H, CH2), 6.88e7.20 (m,
Ar), 13C NMR (CDCl3) (ppm): 8.53 (CH3), 25.30 (Ph-CH3), 44.60
(CH2), 48.32, 52.88 (AreCH2), 123.89e148.77 (Ph; Thioph), 212.90
(C/S).
Scheme 1. Possible bonding modes of ligands involving the thiophene sulfur.
2.3. X-ray crystal structure determination
Single-crystal X-ray data of some of the complexes were
collected on Xcalibur Eos (Oxford) CCD diffractometer using
2.4.1.3. (1) Synthesis of [(C6H5)3Sn{(C6H5)(CH2)}{(C4H3S)(CH2)}
NCS2], 1. A solution of triethylammonium salt of ligand (Bthdtc)
(0.400 g, 1.05 mmol) in methanol (20 mL) was added to triphenyltin
chloride (0.405 g, 1.05 mmol) in methanol (20 mL) with continuous
stirring at room temperature. The solution was stirred for 4 h. The
solvent was evaporated from the reaction mixture. The solid yellow
residue was then extracted with benzene (25 mL) which was
filtered and kept undisturbed at room temperature for crystalliza-
tion. After few days single crystal blocks appeared at the bottom of
round bottomed flask. Yield: 91% (0.593 g) M.p.: 100e101 ꢁC, Anal.
Calc. For C31H23NS3Sn: C, 59.25; H, 4.33; N, 2.23. Found: C, 59.20;
graphite monochromated Mo K
a
radiation (k ¼ 0.71073 Å). The
data integration and reduction were processed with SAINTþ [18]
software. The structures were solved by the direct method and
then refined on F2 by the full matrix least-squares technique with
the SHELXL-97 software [19] using the WinGX (version 1.70.01)
program package [20]. All non-hydrogen atoms were refined
anisotropically. All hydrogen atoms were treated as riding atoms
using SHELX default parameters. Other crystallographic data are
summarized in Table 1. Since the data collections were done at
room temperature the thermal ellipsoids on the carbon atoms are
large leading to large esds on the CeC distances.
H, 4.33; N, 2.21. IR (KBr) (cmꢀ1): 1471
n(C]N), 2923, 3056 n(CeH),
974, 991
n
(C S). 1H NMR (CDCl3) (ppm): 5.12 (s, 2H, CH2), 5.15
(s, 2H, CH2), 6.95e7.75 (m, 20H, Ph; 3H, Thioph), JSnꢀH ¼ 38.57 Hz).
13C NMR (CDCl3) (ppm): 51.59, 56.97 (CH2), 126.27e142.02 (Ph,
Thioph, 1J(119Sne13C) ¼ 568 Hz), 198.67 (C/S), 119Sn NMR (CDCl3)
(ppm): L173.5.
2.4. Syntheses
2.4.1. Synthesis of ligands
2.4.1.1. (A) Bthdtc. A solution of benzyl amine (2.0 g,18.66 mmol) in
methanol (20 mL) was added to thiophene-2-carboxaldehyde
(2.0 g, 17.83 mmol) dissolved in methanol (15 mL) and the reac-
tion mixture was refluxed for 2 h. The solvent was evaporated
under reduced pressure. The resulting yellow liquid was dissolved
in methanol (15 mL) and kept in an ice bath to which a solution of
NaBH4 (2.11 g, 55.77 mmol) in methanol (20 mL) was added drop
wise with stirring. Stirring was continued for 3 h followed by
evaporation of the solvent under reduced pressure. The residue was
washed with water and then extracted with THF (20 mL). The
solvent was removed under reduced pressure and the residue was
dissolved in THF (15 mL). To this solution added a solution of CS2
(1.41 g, 18.55) and triethyl amine (1.88 g, 18.61) in THF (20 mL) drop
wise at w5 ꢁC. The reaction mixture was stirred for 3 h. The solvent
was then evaporated and dried the viscous liquid under vacuum for
2.4.1.4. (2) Synthesis of [(C6H5)3Sn{(C6H4)(CH3)(CH2)}{(C4H3S)(CH2)}
NCS2], 2. A method similar to that described for the synthesis of 1
was adopted for the preparation of 2, however MBthdtc ligand
was used instead of Bthdtc. A solution of MBthdtc (0.600 g,
1.52 mmol) in methanol (20 mL) was added to triphenyltin
chloride (0.587 g, 1.52 mmol) in methanol (20 mL) with contin-
uous stirring at room temperature. After stirring for 4 h the
solvent was evaporated from the reaction mixture and the
residue was extracted with benzene (25 mL) and the solution was
kept under ambient conditions for crystallization. After few days
cuboids of single crystals appeared at the bottom of round
bottomed flask. Yield: 92% (0.920 g) M.p.: 99e101 ꢁC. Anal. Calc.
for C32H25NS3Sn: C, 59.82; H, 4.55; N, 2.18. Found: C, 59.68; H,
4.49; N, 2.16. IR (KBr) (cmꢀ1) 1462
n(C]N), 2875, 2924, 3058
3 h/1 mm Hg. Yield- 94%. IR (KBr) (cmꢀ1) 1495
3028, 3063, 3313 (CeH), 951
n(C]N), 2833, 2919,
(C S). 1H NMR (CDCl3) (ppm): 2.36 (s, 3H,
n
n
(C S) 1H NMR (CDCl3)
n
(CeH), 970, 986
n
CH3), 5.07 (s, 2H, CH2), 5.14 (s, 2H, CH2), 6.96e7.75 (m, 20H, Ph;
3H, Thioph), JSnꢀH ¼ 43.71 Hz). 13C NMR (CDCl3) (ppm): 21.16
(ppm):1.40e1.45 (t, 3H, CH3, JHeH ¼ 7.2 Hz), 3.27e3.34 (q, 2H, CH2,
JHeH ¼ 7.5 Hz), 5.45 (s, 2H, CH2), 5.49 (s, 2H, CH2), 6.90e7.33 (m, Ar),
Table 1
Crystallographic data and structure refinements.
Compound
1
2
3
4
6
7
Space group
a (Å)
b (Å)
Pꢀ1
Pꢀ1
C2
Pꢀ1
P21/c
Pꢀ1
8.6336(16)
9.8645(18)
17.462(3)
77.75(3)
84.552 (3)
73.195 (3)
1390.3(4)
1.165
9.1424(14)
10.0017(16)
17.197(3)
102.927(2)
91.756 (3)
109.639(2)
1433.8(4)
1.131
18.7796(11)
7.0397(2)
16.0829(8)
90
124.907(8)
90
10.235(7)
11.402(8)
14.169(10)
79.37(1)
78.24(1)
78.14(1)
1566.7(19)
1.237
14.6930(6)
20.2874(6)
11.2538(5)
90
111.363(5)
90
8.7328(15)
9.8710(17)
17.411(3)
77.621(3)
84.628(3)
72.561(3)
1397.9(4)
6.278
c (Å)
a
b
g
(ꢁ)
(ꢁ)
(ꢁ)
V(Å3)
1743.7(2)
1.116
3124.1(2)
1.410
m
mmꢀ1
F(000)
636
652
898
724
1496
693
Crystal size (mm)
0.20 ꢂ 0.14 ꢂ 0.09
2.29e28.39
1.048
0.16 ꢂ 0.14 ꢂ 0.10
2.26e28.35
1.081
0.18 ꢂ 0.16 ꢂ 0.14
2.65e28.08
0.965
0.13 ꢂ 0.11 ꢂ 0.08
2.19e28.67
1.067
0.14 ꢂ 0.10 ꢂ 0.8
2.01e28.79
1.003
0.15 ꢂ 0.12 ꢂ 0.10
2.21e28.39
1.051
q
Range
GOF
R1
0.0363
0.0404
0.0358
0.0662
0.0481
0.0422

N. Singh, S. Bhattacharya / Journal of Organometallic Chemistry 700 (2012) 69e77
71
(CH3), 51.36, 56.73 (CH2), 126.23e142.08 (Ph; Thioph)
1J(119Sne13C) 571 Hz), 198.38 (C S), 119Sn NMR (CDCl3)
(ppm): ꢀ174.9.
for C31H23NS3Pb: C, 51.93; H, 3.80; N, 1.95. Found: C, 51.90; H,
3.82; N, 1.99. IR (KBr) (cmꢀ1) 1462
(C]N), 2857, 2924, 3058
(CeH), 970, 995
(C/S). 1H NMR (CDCl3) (ppm): 5.17 (s, 2H,
CH2), 5.21 (s, 2H, CH2), 6.94e8.03 (m, 20H, Ph; 3H, Thioph).
13C NMR (CDCl3) (ppm): 51.79, 57.01 (CH2), 125.99e158.32
(Ph; Thioph), 201.19 (C S)
¼
n
n
n
2.4.1.5. (3) Synthesis of [(CH3CH2CH2)2Sn{(C6H5)(CH2)}2{(C4H3S)
(CH2)}2(NCS2)2], 3. A method similar to that described for the
synthesis of 1 was adopted, however, dipropyltin dichloride (0.5
equivalents) was used instead of triphenyltin chloride. Needle shaped
colourless single crystals were isolated. Yield: 89% (0.570 g) M.p.:
82e83 ꢁC. Anal. Calc. for C32H30N2S6Sn: C, 50.45; H, 5.03; N, 3.68.
3. Results and discussion
3.1. Preparation and spectroscopic characterization of complexes 1e7
Found: C, 50.48; H, 5.01; N, 3.66. IR (KBr) (cmꢀ1) 1462
2926, 3022, 3060 (CeH), 962, 934
(C S).1HNMR(CDCl3)(ppm):1.12
n(C]N), 2856,
n
n
Six new tin/organotin 1e6 and one organolead dithiocarbamate
7 compounds have been isolated as shown in Scheme 2. The
synthetic reactions involved treatment of the appropriate organo-
tin(IV) chlorides (Ph3SnCl, Pr2SnCl2, Me2SnCl2, BuSnCl3 and SnCl4)
with stoichiometric amounts of triethylammonium salt of ligands
in methanol. The tin(IV) complex Cl2Sn(Bthdtc)2 was obtained in an
attempt to prepare the homoleptic tin(IV) complex, Sn(Bthdtc)4.
Notably, the latter could not be synthesised by treating SnCl4 with
the ligand salt in 1:4 M ratio even in refluxing methanol, possibly
due to the high steric bulk of the ligands. A search in the literature
revealed that a few tin tetrakis-dithiocabramates are known and
have been prepared conveniently under ambient conditions [21].
An organolead dithiocarbamate compound 7 was also isolated by
an analogous reaction using triphenyllead chloride. All the
compounds were characterized by elemental analysis, FT-IR, and
multinuclear NMR (1H, 13C and 119Sn) spectroscopy and single
crystal X-ray diffraction analysis.
(t, 3H, CH3, JHeH ¼ 6.9 Hz) 2.05(m, 2H, CH2), 2.25(t, 2H, CH2,
JHeH ¼ 7.2 Hz) 5.12 (s, 2H, CH2), 5.18 (s, 2H, CH2), 6.96e7.38 (m, 10H,
Ph; 6H, Thioph). 13C NMR (CDCl3) (ppm): 18.09 (CH3), 20.28,
38.49 1J(119Sne13C)
¼
226.4 Hz, (CH2), 50.32, 55.44 (CH2),
126.24e137.22 (Ph; Thioph), 197.36 (C S), 119Sn NMR (CDCl3) (ppm):
L336.9.
2.4.1.6. (4) Synthesis of [(CH3)2Sn{(C6H5)(CH2)}2{(C4H3S)(CH2)}2
(NCS2)2], 4. A method similar to that described for the synthesis of 1
was adopted; however, dimethyltin dichloride (0.5 equivalents) was
used instead of triphenyltin chloride. Colourless single crystals were
obtained. Yield: 90% (0.583 g) M.p.: 138e140 ꢁC. Anal. Calc. for
C28H22N2S6Sn: C, 47.66; H, 4.29; N, 3.97. Found: C, 47.62; H, 4.29; N,
3.95. IR (KBr) (cmꢀ1) 1462
n(C]N), 2855, 3021, 3067 n(CeH), 975, 989
n
(C S). 1H NMR (CDCl3) (ppm): 1.68 (s, 3H, SneCH3, JSneH ¼ 45 Hz),
5.10 (s, 2H, CH2), 5.15 (s, 2H, CH2), 6.97e7.39 (m, 10H, Ph; 6H, Thi-
oph). 13C NMR (CDCl3) (ppm): 16.02 (SneCH3), 50.31, 55.51 (CH2),
126.24e137.04 (Ph; Thioph), 202.34 (C S), 119Sn NMR (CDCl3)
(ppm): ꢀ332.4.
IR spectroscopy has been used as a diagnostic tool to study the
bonding mode of dithiocarbamate ligands. The ligand is known to
bind with a metal atom monodentately as well as bidentately. The
former case displays a characteristic strong absorption band
2.4.1.7. (5) Synthesis of [(CH3CH2CH2CH2)Sn{(C6H5)(CH2)}3{(C4H3S)
(CH2)}3(NCS2)3], 5. A method similar to that described for the
synthesis of 1 was adopted, however, n-butyltin trichloride (0.33
equivalents) was used instead of triphenyltin chloride. Needle shaped
crystals were obtained. Yield: 85% (0.383 g) M.p.: 140e141 ꢁC. Anal.
Calc. for C43H33N3S9Sn: C, 51.08; H, 4.49; N, 4.16. Found: C, 51.0; H,
below 1485 cmꢀ1 due to
n
(C N) vibrations. In the case of
a bidentate mode of binding the (C N) stretching appears above
1485 cmꢀ1 and a single band due to (C S) around 1000 cmꢀ1
n
[22e24]. According to Bonati and Ugo [25] the C S stretching
vibrational mode appearing in the range of 950e1050 cmꢀ1 with
bonding type of CS2 moiety proposed that the single symmetrical
peak in this region is indicative of bidentate coordination where
as splitting in peak indicate the monodentate or anisobidentate
bonding.
4.49; N, 4.18. IR (KBr) (cmꢀ1) 1474
n(C]N), 2724, 2782; 2858, 2925
3032, 3071 (CeH), 975, 923
n
n
(C S). 1H NMR (CDCl3) (ppm): 0.94 (t,
3H, CH3, JHeH ¼ 7.2 Hz), 1.44e1.53 (m, 2H, CH2), 1.77e1.87 (m, 2H,
CH2), 2.11e2.17 (t, 2H, CH2, J ¼ 7.4 Hz), 4.99 (s, 2H, CH2), 5.02 (s, 2H,
CH2), 6.98e7.37 (m, (15H, Ph; 9H, Thioph). 13C NMR (CDCl3) (ppm):
13.84 (CH3), 25.29 (CH2), 28.50 (CH2, 1J(119Sne13C) ¼ 777.13 Hz),
47.58 (CH2), 51.76, 57.32 (CH2), 126.77e135.55 (Ph; Thioph), 201.48
(C S), 119Sn NMR (CDCl3) (ppm): ꢀ574.6.
The infrared spectra of all the seven dithiocarbamate
compounds showed very intense absorption assignable to n(C N)
vibration in the region 1450e1500 cmꢀ1. The dithiocarbamate
ligands bind to the metal monodentately using only one sulphur
atom showing a pair of bands due to n
(C S) below 1000 cmꢀ1 in all
the six organometallic compounds. Interestingly, only dichlorotin
dithiocarbamate compound exhibited spectral features corre-
2.4.1.8. (6) Synthesis of [Cl2Sn{(C6H5)(CH2)}2{(C4H3S)(CH2)}2(NCS2)2],
6. A method similar to that described for the synthesis of 1 was
adopted, however, tin tetrachloride (0.25 equivalents) was used
instead of triphneyltin chloride. Yellow single crystal rods were
isolated. The resulting product was the same even after taking the
metal salt and ligand in 1:2 stoichiometric ratio. Yield: 90%
(0.220 g) M.p.: 118e120 ꢁC. Anal. Calc. for C26H16N2Cl2S6Sn: C,
41.83; H, 3.24; N, 3.75. Found: C, 41.89; H, 3.22; N, 3.74. IR (KBr)
sponding to
symmetrical peak at 970 cmꢀ1 for
1493 cmꢀ1 for
(C N). Notably, the triethylammonium salts of the
ligands showed a strong C N stretching band at 1495e1496 cmꢀ1
and a single peak at 950e951 cmꢀ1 due to
(C S) vibration which is
a
bidentate mode of binding having
a single
n
(C S) and a vibration at
n
n
consistent with the dianionic canonical form.
The 1H NMR spectrum of all the seven compounds exhibited
two peaks in the range of 4.93e5.21 and 6.95e8.03 ppm for eCH2
groups and phenyl, thiophene rings respectively. In a given series
of compounds the chemical shift values in the 119Sn NMR spectra
have been observed to move upfield as the coordination number
of tin increases from four to seven [26]. In tetrahedral compounds
the 119Sn signal is usually observed between þ200 and ꢀ60 ppm
while the same for pentacoordinate and hexacoordinate tin
appears in the ranges ꢀ90 to ꢀ190 ppm and ꢀ210 to ꢀ400 ppm
respectively [27]. 119Sn signal in the NMR spectrum of the
compounds 1 and 2 clearly indicated the existence of five
(cmꢀ1) 1493
n(C]N), 2855, 2927, 3028, 3098 n(CeH), 970 n(C S).
1H NMR (CDCl3) (ppm): 4.93 (s, 2H, CH2), 4.96 (s, 2H, CH2),
7.01e7.44 (m, (10H, Ph; 6H, Thioph)). 13C NMR (CDCl3) (ppm):
52.68, 58.45 (CH2), 127.12e134.38 (Ph; Thioph), 198.729 (C S).
2.4.1.9. (7)Synthesis of [(C6H5)3Pb{(C6H5)(CH2)}{(C4H3S)(CH2)}(NCS2)],
7. A method similar to that described for the synthesis of 1 was
adopted, however, triphenyllead chloride (1.0 equivalent) was
used instead of triphneyltin chloride. Light yellow single crystals
were obtained. Yield: 86% (0.811 g) M.p.: 128e129 ꢁC. Anal. Calc.

72
N. Singh, S. Bhattacharya / Journal of Organometallic Chemistry 700 (2012) 69e77
Scheme 2. Preparation of the ligands and complexes.
coordinated tin in both the cases. (cf. ꢀ46.5 ppm for Ph3SnCl)
[28]. The signal observed in the cases of 3 and 4 are suggestive of
the presence of six coordinate tin while the signal at ꢀ574.6 ppm
evinced for a seven coordinated tin in compound 5. 1J(119Sne13C)
values have been used to calculate CeSneC angles in solution
[29]. The CeSneC angles in 1 and 2 were found to be 127ꢁ which
suggests a trigonal bipyramidal geometry around Sn(IV). On the
other hand, the CeSneC angle is 97ꢁ in complex 3 indicating cis-
3.2. Crystal and molecular structures
Single crystals suitable for X-ray diffraction analysis of all the
compounds, except one (5), could be grown. The details of crys-
tallographic data and structure refinement are given in Table 1.
3.2.1. (a) Molecular structure of 1
Molecular structure and numbering scheme of 1 is given in
Fig. 1. As can be seen from the structure (Fig. 1) the dithiocarbamate
ligand (Bthdtc) binds to the metal primarily in a monodentate
fashion. Several organotin compounds containing one or more
dithiocarbamates are known which reveal that these ligands are
rarely symmetrically bound to the tin [30e35]. In the present case
Sn1eS3 is a normal covalent bond with a bond distance of 2.48 Å,
while the Sn1eS2 distance is very long (3.04 Å). The latter is
however, significantly shorter than the sum of the van der Walls’
radii of the two atoms (3.97 Å) indicating the possibility of a weak
bonding interaction between the two. The SneC bonds vary
between 2.11 and 2.16 Å which are well within the usually observed
CeSn distances in organotin compounds.
orientation of the two organyl groups in
environment.
a hexacoordinate
From the NMR spectral features one would conclude the
bidentate bonding of the dithiocarbamate ligands in all these
complexes, which is not in consistence with the IR spectral
features. Though the possibility of structural differences in solu-
tion and solid state can not be ruled out, the IR spectral pattern
may also indicate an anisobidentate bonding of the dithiocarba-
mate ligands. To get further insight we have recorded 119Sn NMR
data of a representative compound at a higher temperatures also.
A downfield shift was observed in the spectrum of 3 when
recorded at 45 ꢁC (
d
¼ ꢀ333 ppm) suggesting that with increase in
temperature there is some change in coordination environment.
Which is possibly because of the anisobidentate bonding of the
ligands; the weak SneS bonds become weaker with increase in
temperature.
The structure of 1 is comparable to that of [Ph3Sn(S2CNEt2)]
where the longer Sn/S distance is 3.11 Å [36]. Hall and Tiekink have
shown how the electron donating/withdrawing effect of the ligands
bound to tin markedly affect both the anisobidentate nature of the

N. Singh, S. Bhattacharya / Journal of Organometallic Chemistry 700 (2012) 69e77
73
Fig. 1. Molecular structure of 1. Selected bond lengths (Å) and bond angles (ꢁ): S1eC09 ¼ 1.676(13), S1eC12 ¼ 1.708(10), Sn1eS3
¼
2.4753(8), N01eC08
115.04(8), C25eSn1eS3
¼
1.472(4),
117.14(8),
Sn1eC19
¼
2.122(3), C19eSn1eC25
¼
115.84(11), C19eSn1eC31
¼
107.10(11), C25eSn1eC31
¼
105.22(11), C19eSn1eS3
¼
¼
C31eSn1eS3 ¼ 92.52(8), N01eC13eS3 ¼ 117.8(2), S2eC13eS3 ¼ 119.21(16).
SneS chelation (
D
SneS) and the solid state structure for compounds
tin expand the angles towards the 120ꢁ expected for equatorial
substituents [C19eSn1eC25 ¼ 116.32, S3eSn1eC25 ¼ 116.64ꢁ]
where as the substituents placed at axial site subtend a much
wider angle (S2eSneC31 ¼156.75ꢁ). On the other hand the atoms at
axial and equatorial sites subtend angles smaller than the ideal
of the type R2Sn(S2CNR’2)2 (R ¼ alkyl, aryl, vinyl, chloride; R0 ¼ alkyl)
[37]. The coordination geometry around tin in 1 is deviated from
that of a regular tetrahedron towards a trigonal bipyramid may be
due to the weak Sn1eS2 interaction. The atoms/groups bonded to
Fig. 2. Molecular structure of 2. Selected bond lengths (Å) and bond angles (ꢁ):S2eC1 ¼ 1.682(3), S1eC1 ¼ 1.759(3), Sn1eC15 ¼ 2.133(3), Sn1eS1 ¼ 2.4885(9), N1eC1 ¼ 1.334(4),
C15eSn1eC27 ¼ 120.08(12), C15eSn1eC21 ¼ 106.48(12), C27eSn1eC21 ¼ 101.22(12), C15eSn1eS1 ¼ 115.35(9), N1eC1eS1 ¼ 118.5(2), S2eC1eS1 ¼ 118.99(19).

74
N. Singh, S. Bhattacharya / Journal of Organometallic Chemistry 700 (2012) 69e77
Fig. 3. Molecular structure of 3. Selected bond lengths (Å) and bond angles (ꢁ):S03eC13 ¼ 1.693(5), S02eC13 ¼ 1.738(6), Sn01eC14 ¼ 2.145(6), Sn01eS02 ¼ 2.5391(13),
Sn01eS02
S03eC13eS02 ¼ 119.3(4).
¼
2.5391(13), N01eC13
¼
1.346(7), C14eSn01eC14
¼
138.8(4), C14eSn01eS02
¼
106.18(19), S02eSn01eS02
¼
84.06(6), N01eC13eS03
¼
121.3(4),
tetrahedral angle (C25eSn1eS2 ¼ 87.87ꢁ, C19eSn1eC31 ¼ 107.13ꢁ,
S3eSn1eC31 ¼ 91.51ꢁ). 119Sn NMR spectrum of the compound
clearly indicated that the Sn atom present in this compound is five
coordinated.
scheme is given in Fig. 3. The coordination sphere around the tin
atom in the compound can be described as a highly distorted
tetrahedron. However, the alternative descriptions could be that of
a bicapped tetrahedron or a skew trapezoidal bipyramid. The latter
merits some comments. The four sulfur atoms constitute a trape-
zoid and the two propyl groups occupy the axial positions to
complete the six coordination of the tin atom. This model is based
on the presumption that the dithio ligand chelates the tin center
in an asymmetric way. The anisobidentate mode of coordination in
this compound is accompanied by unequal SneS bond distances.
The two strong Sn01eS02 bonds (2.54 Å) are cis to each other with
a very acute angle S02eSn01eS02 (84.06ꢁ). The weaker Sn01eS03
(2.96 Å) bonds with S03eSn01eS03 angle of 146.94ꢁ deviate only
by w33ꢁ from being linear. The Sn01eS03 (2.96 Å) distance is
quite longer than the sum of covalent radii of Sn and S atoms
(2.42 Å) but significantly less than the sum of van der waals radii
of these atoms (3.97 Å). The Sn01eS02 bond length is much
3.2.2. (b) Molecular structure of 2
The molecular structure of 2 (Fig. 2) is identical to that of 1. The
anion of a binds to tin basically in a monodentate fashion and the
two SneS distances are highly unequal Sn1eS2 is longer (2.96 Å)
than Sn1eS3 (2.49 Å). However, the coordination environment
about tin in this complex is also distorted from the ideal tetrahedral
geometry and can be described as a distorted trigonal bipyramid
considering the S2 atom within the coordination sphere.
3.2.3. (c) Molecular structure of 3
Dipropyltin bis-dithiocarbamate 3 crystallizes in monoclinic
system with space group C2. Molecular structure and numbering
Fig. 4. Molecular structure of 4. Selected bond lengths (Å) and bond angles (ꢁ):S1eC3 ¼ 1.755(15), S2eC3 ¼ 1.666(18), S3eC15 ¼ 1.6454(7), S4eC18 ¼ 1.704(17), C18eS5 ¼ 1.680(16),
C28eS6 ¼ 1.8279(11), Sn1eC1 ¼ 2.13(2), Sn1eS1 ¼ 2.520(5), Sn1eS4 ¼ 2.532(5), N1eC4 ¼ 1.44(2), C2eSn1eC1 ¼ 139.6(10), C2eSn1eS1 ¼ 107.7(7), C1eSn1eS1 ¼ 104.5(6),
C1eSn1eS4 ¼ 101.6(7), S1eSn1eS4 ¼ 83.27(14), C15eS3eC12 ¼ 104.44(4), N1eC3eS1 ¼ 116.6(12), S2eC3eS1 ¼ 119.6(10).

N. Singh, S. Bhattacharya / Journal of Organometallic Chemistry 700 (2012) 69e77
75
atoms at the corners of the trapezoid. The two methyl groups
occupy the axial sites subtending an angle of 135.26ꢁ resembling
the cisetrans pathway which starts forming at about a CeSneC
angle of 134ꢁ.
As observed in 3 there are two strong SneS bonds with shorter
bond lengths (2.53 and 2.52 Å) and two weak SneS bonds with
longer bond lengths (2.99 and 2.94 Å). The two strong SneS bonds
are cis to each other subtending an acute angle of 83.26ꢁ. The
weaker SneS bonds with S2eSn01eS1 angle of 147.75ꢁ lie 32ꢁ less
from being co-linear to each other. The two SneS bond lengths,
(S1eSn01 ¼ 2.52 Å and S2eSn01 ¼ 2.53 Å) are longer than the sum
of the covalent radii of the tin and sulfur (2.42 Å) but significantly
below the sum of the van der Waals radii of these atoms (4.0 Å).
3.2.5. (e) Molecular structure of 6
In SnCl2(Bthdtc)2 due to the bulkiness of the ligand only two Cl
atoms are substituted by the ligands and two Cl atoms remain intact
to the metal atom. As can be seen from the crystallographic data, it
crystallizes in monoclinic system with space group P21/c. Molecular
structure and numbering scheme is shown in Fig. 5. This is the only
compound of this series in which the dithiocarbamate ligands
behave as a bidentate species and chelate the tin atom by means of
both the sulfur atoms giving a cis-octahedral geometry around the
tin atom. Distortion from the regular octahedral structure is possibly
due to the small ligand bites of the dithiocarbamate ligands which
can not span the ideal cis angle of 90ꢁ. SneS distances are not exactly
equal, and the SeC bond distances also vary accordingly. However,
the difference in SneS distance in a Snedithiocarbamate unit is not
very significant (SneS01 ¼ 2.51; SneS02 ¼ 2.57 Ǻ). The longer SeC
bond (1.74 Å) is associated with shorter SneS bond and the shorter
CeS bond (1.71 Å) is associated with the longer SneS bond. The SeC
bond lengths are noticeable in the dithiocarbamate groups being
intermediate between the values expected for single and double
bonds. C N bond distances are also in their usual bonding range of
1.31e1.32 Å and are shorter than those observed in the structures of
1e4 (ranging between 1.32 and 1.35 Å) in consistence with the
bidentate mode of ligand bonding. The two SneCl bonds are almost
equal (2.38 and 2.39 Å) and are comparable to the sum of the
covalent radii of the two atoms (2.38 Å). Weak interactions such as
hydrogen bonding along c axis in crystal lattice (of 6) have been
clearly shown in Fig. 6.
Fig. 5. Molecular structure of 6. Selected bond lengths (Å) and bond angles
(ꢁ):S1eC14 ¼ 1.734(8), S2eC14 ¼ 1.714(8), S3eC13 ¼ 1.729(8), S4eC13 ¼ 1.731(9),
Sn1eCl1 ¼ 2.390(3), C9eS5 ¼ 1.705(13), C23eS6 ¼ 1.677(18), Sn1eCl2 ¼ 2.371(3),
Sn1eS1 ¼ 2.514(2), Sn1eS2
¼
2.569(2), Sn1eS3
92.17(11), Cl2eSn1eS4
92.79(9), Cl1eSn1 S1
163.42(10), Cl1eSn1eS2
¼
2.587(2), Sn1eS4
¼
2.511(2),
N1eC13 1.321(10), Cl2eSn1eCl1
¼
¼
¼
102.52(10),
102.09(9),
Cl1eSn1eS4
S4eSn1eS1
¼
91.58(9), Cl2eSn1eS1
159.10(7), Cl2eSn1eS2
¼
¼
¼
¼
¼
¼
93.61(9),
S4eSn1eS2 ¼ 92.85(8), S1eSn1eS2 ¼ 70.81(7).
shorter (2.54 Å) and is definitely a covalent bond but it will not be
inappropriate to infer that a bonding interaction exists between
Sn01 and S03 atoms. The CeSneC angle (138.79ꢁ) is far from ideal
angles of both tetrahedron and octahedron. In skew trapezoidal
bipyramidal molecules the CeSneC angles in cis-diorganotin
complexes are in the range of 102e110ꢁ while the same range
between 180ꢁ and 145ꢁ in the case of trans- isomers. Since the
C1eSneC2 angle in 3 is 138.79ꢁ. It may be considered to resemble
the transition state of the cis-trans pathway which starts forming
at about a CeSneC angle 134ꢁ.
3.2.4. (d) Molecular structure of 4
The molecular structure of 4 is very much similar to that of 3. It
crystallizes in triclinic system with space group P-1. Molecular
structure and numbering scheme is shown in Fig. 4. In this
compound also the dithiocarbamate ligands bind to tin in aniso-
bidentate fashion. The asymmetry in bonding of the ligand is also
reflected in carbonesulphur bond distances for both the ligand
moieties which are not equal (1.67 and 1.73 Å). The thiocarbonyl
sulfur atoms of the ligands weakly interact to the metal leading to
a distorted structure. The compound adopts a skew trapezoidal
bipyramidal structure with the Sn atom at the centre and four S
3.2.6. (f) Molecular structure of 7
Compound 7 crystallizes in triclinic system with space group
P-1. In this complex the dithiocarbamate ligand binds to the lead
Fig. 6. Arrangement of molecules along c axis in lattice showing weak interactions.

76
N. Singh, S. Bhattacharya / Journal of Organometallic Chemistry 700 (2012) 69e77
Fig. 7. Molecular structure of 7. Selected bond lengths (Å) and bond angles (ꢁ): S01eC19 ¼ 1.683(6), S02eC19 ¼ 1.754(6), Pb01eC05 ¼ 2.193(5), Pb01eS02 ¼ 2.5682(15),
N01eC027
S01eC19eS02 ¼ 121.2(3).
¼
1.466(7), C05ePb01eC13
¼
118.6(2), C05ePb01eC12
¼
107.1(2), C13ePb01eC12
¼
108.7(2), C05ePb01eS02
¼
113.02(15), C19eS02ePb01
¼
98.19(19),
atom in monodentate fashion. The structure (Fig. 7) of this
compound is very much similar to that of 1. Like organotin dithio
complexes organolead dithio complex also possesses tetrahedral
geometry. The distortion in tetrahedral geometry is evinced by the
angles about the Pb atom. The CeS bond lengths are comparable to
the corresponding bond lengths in 1 and 2. Intermolecular weak
interactions are significantly present in this compound which can
be seen in Fig. 8.
4. Thermogravimetric analysis
We have carried out TGA analysis of 1, 6 and 7 at atmospheric
pressure under N2 flow. The TGA of 1 and 7 showed formation of SnS
and PbS at about 350 ꢁC with weight loss of compounds w76% and
w67% while in compound 6, different weight losses at 150 ꢁC, 260 ꢁC
and 400 ꢁC have been observed (Fig. 9) and it is not possible to make
a guess about the end product from the percentage weight loss.
Fig. 8. Arrangement of molecules (of 7) along an axis in a lattice showing intermolecular interactions.

N. Singh, S. Bhattacharya / Journal of Organometallic Chemistry 700 (2012) 69e77
77
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fungal, and cytotoxicity of diorganotin(IV) complex derived from Bu2Sn(acac)2
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[13] Thiuram-anddithiocarbamate-acceleratedsulfurvulcanizationfromthechemist’s
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[14] M. Cicotti, Handbook of residue analytical methods for agrochemicals, vol. 2,
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[15] Synthesis, characterisation and thermal decomposition of tin(IV) dithiocar-
bamate derivatives
e single source precursors for tin sulfide powders.
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A.C. Doriguetto, J. Ellena Polyhedron 23 (2004) 2103e2109
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37 (1998) 3753e3758
Fig. 9. TGA plot of 1, 6 and 7 (Compound 1 and 7 showing formation of SnS and PbS).
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Organic Chemistry, fifth ed. Vogel, Dorling Kindersley, India, 2006.
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5. Conclusion
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G. Durgaprasad, D.N. Sathyanarayana, C.C. Patel Can. J. Chem. 47 (1969) 631e635
In conclusion, the bonding of the dithiocarbamate ligands was
found to vary from anisobidentate to bidentate according to the
nature of the co-ligands present on the metal. In none of the cases
the sulfur atom of the thiophene ring is involved in bonding with
the metal. Very recent studies from our laboratory have showed
that the thiophene sulfur carries a partial positive charge in the case
of thiophene-2-thiocarboxylates and a dative bond from this sulfur
is not quite favourable [38]. The triphenyltin and triphenyllead
dithiocarbamates can be used as single source precursors for the
preparation of the corresponding metal sulfides.
[24] Is infrared spectroscopy
a
reliable guide to the tin-sulfur interaction in
research note. S. Chandra, R.J. Magee,
organotin dithiocarbamates?
A
B.D. James Main Group Met. Chem. 11 (1988) 57e65
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J. Organomet. Chem. 10 (1967) 257e268
[26] Octahedral dialkyltin complexes:
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Appendix A. Supplementary material
[27] Syntheses, crystal structures and coordination modes of tri- and di-organotin
derivatives with 2-mercapto-4-methylpyrimidine. C. Ma, J. Zhang, G. Tian,
R. Zhang J. Organomet. Chem. 690 (2005) 519e533
CCDC Nos. 797141, 797139, 797142, 797140, 797143 and 834820
contain the supplementary crystallographic data for 1, 2, 3, 4, 6 and
7 respectively. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
[28] Studies of organotin(IV)-orthoquinone systems. M.A. Brown, B.R. McGarvey,
A. Ozarowski, D.G. Tuck J. Organomet. Chem. 550 (1998) 165e172
[29] Structural investigations by solid state C-13NMR. Dependence of
[1J(119Sn-13C)] on the methyltin-methyl angle in methyltin(IV)s. T.P. Lockhart,
W.F. Manders, J.J. Zuckerman J. Am. Chem. Soc. 107 (1985) 4546e4547
[30] The importance of varying the Lewis acidity of R2Sn in determining the
molecular structure of R2Sn(1,1-dithiolate) compounds: the crystal and
molecular structures of three divinyltin N, N-dialkyldithiocarbamates.
V.J. Hall, E.R.T. Tiekink Main Group Met. Chem. 21 (1998) 245e254
[31] Crystal and molecular structures of diphenyltin(IV) bis(N, N-dicyclohex-
yldithiocarbamate) and diphenyltin(IV) bis(N-cyclohexyl, N-ethyldithiocar-
bamate). V.J. Hall, E.R.T. Tiekink Main Group Met. Chem. 18 (1995) 611e620
[32] Phenyltin diethyldithiocarbamates: solid state and solution structures and
in vitro anti- tumor activity. J.M. Hook, B.M. Linahan, R.L. Taylor, E.R.T. Tiekink,
L. van Gorkom, L.K. Webster Main Group Met. Chem. 17 (1994) 293e311
[33] Stereochemical nonrigidity and ligand dynamics in hypervalent tin(IV)
compounds. Heteronuclear NMR and crystallographic studies of tri-
organoyltin(IV) and diorganoyltin(IV) complexes with dithiolate ligands.
D. Dakternieks, H. Zhu, D. Masi, C. Mealli Inorg. Chem. 31 (1992) 3601e3606
[34] Structure of di(tert-butyl)bis(N, N-dimethyldithiocarbamato)tin(IV). K. Kim,
J.A. Ibers, O.-S. Jung, Y.S. Sohn Acta Crystallogr. Sect. C. C43 (1987) 2317e2319
[35] Tris(N, N-diethyldithiocarbamato-S, S’)phenyltin. E. Kellö, V. Vrabel, I. Skacani
Acta Crystallogr. Sect. C: Cryst. Struct. Commun. 51 (1995) 408e410
[36] Crystal and molecular structure of bis(N, N0-diethyldithiocarbamato)diphe-
nylstannane, C22H30N2S4Sn. P.F. Lindley, P. Carr J. Cryst. Molec. Struct. 4 (1974)
173e185
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