Influence of functionalities on the structure and luminescent properties of organotin(IV) dithiocarbamate complexes

Article abstract of DOI:10.1016/j.jorganchem.2015.03.034

Five new organotin(IV) dithiocarbamate complexes of the form R₂SnL₂ (R = ⁿBu, L = L1, (4-phenylpiperazine-1-dithiocarbamate) 1, L2, (N-benzyl-N′-methyl-4-pyridyldithiocarbamate) 2; Ph, L3, (N-benzyl-N′-methyl-3-pyridyldith

Full text of DOI:10.1016/j.jorganchem.2015.03.034

Journal of Organometallic Chemistry 787 (2015) 65e72
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Influence of functionalities on the structure and luminescent
properties of organotin(IV) dithiocarbamate complexes
Ajit N. Gupta a, Vinod Kumar a, Vikram Singh a, Amit Rajput b, Lal Bahadur Prasad a,
,
*
Michael G.B. Drew c, Nanhai Singh a
a Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221005, India
b Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India
c Department of Chemistry, University of Reading, Whiteknights, Reading, RG6 6AD UK
a r t i c l e i n f o
a b s t r a c t
Five new organotin(IV) dithiocarbamate complexes of the form R2SnL2 (R ¼ nBu, L ¼ L1, (4-phenylpiperazine-
1-dithiocarbamate) 1, L2, (N-benzyl-N0-methyl-4-pyridyldithiocarbamate) 2; Ph, L3, (N-benzyl-N0-methyl-
3-pyridyldithiocarbamate) 3) and Ph3SnL (L ¼ L4, (N,N0-di(methyl-3-pyridyldithiocarbamate)) 4, L5, (4-
ethoxycarbonylpiperidine-1-dithiocarbamate) 5) have been synthesized and characterized by elemental
analysis, spectroscopy (IR, UVeVis., 1H, 13C and 119Sn NMR) and their structures have been investigated by
single crystal X-ray crystallography. In (1,2) the structure has C2 symmetry with the tin atom in a highly
distorted octahedral six-coordinate geometry inwhich the bidentateligands are asymmetrically bonded and
the two nBu groups subtend an angle at the metal of 140.7(1),141.4(3)ꢀ. By contrast 3, also with C2 symmetry,
with phenyl substituents, is closely octahedral. In 3 the Py(N) on the dtc backbone interacts with the H37 on
the adjacent molecule via unconventional CeH/N hydrogen bonding forming a six membered benzene like
(C2H2N2) structure. In 4 and 5 five coordinate TBP geometry is established; 4 contains two molecules in the
asymmetric unit (4A and 4B). In 4 the Py(N) on the dithiocarbamate unit uniquely interacts with the tin atom
Article history:
Received 4 February 2015
Received in revised form
28 March 2015
Accepted 30 March 2015
Available online 20 April 2015
Keywords:
Organotin(IV)
Dithiocarbamate
Photoluminescent
Theoretical calculations
Thermogravimetric analysis
ontheneighbouring moleculewith Sn/N contactsat 3.11 Å. TheCeH/p (CG)interactions between CG of4A
and H34 of 4B are also observed. These interactions have been supported by theoretical calculations. All the
complexes luminesce in CH2Cl2 solution at room temperature except for 1; the strongest luminescent
behaviour is found in 4. TGA analysis of 3 and 5 show a double and single step decomposition respectively.
© 2015 Elsevier B.V. All rights reserved.
Introduction
commonly they can bind to a metal in a chelating-bridging and
monodentate fashion.
Transition and main group metal 1,1-dithiolates particularly that
of dithiocarbamate ligands have been extensively studied because
of their structural diversities, magnetic, optical and conducting
properties and multifarious applications as sensitizers in solar en-
ergy conversion schemes, single source precursors for the forma-
tion of metal sulphides, flotation agents in metallurgy, oil additives,
vulcanization accelerators in rubber technology, herbicides and
pesticides etc [1e10].
The variety of structures and multifaceted chemistry of the
monoanionic dithiocarbamate ligands may be viewed to the reso-
nance structures (Fig. 1c) they exhibit in their complexes. The
dithiocarbamate ligands are generally S,S- chelating due to domi-
nant contribution of the resonance form c (Fig. 1) but less
The growing interest in the dithiocarbamate complexes stems
due to functionalization of the R groups on the nitrogen atom of the
dithiocarbamate backbone which may result in more intriguing
structures and may tune their physical properties. The resurgence of
interest in hypervalent tin(IV)/organotin(IV) dithiocarbamate com-
plexes in recent years is due to their rich variety of structures and
applications in fields as diverse as agriculture, biology, catalysis and
their use as single source precursors to tin sulphide materials (SnS,
SnS2, and Sn2S3) [8,11]. The design and development of dithiocar-
bamate ligands functionalized with additional donor groups
enabling expanded bonding capabilities have not been a focus of
research investigation for a long time. The majority of tin(IV)/orga-
notin(IV) complexes reported until recently have been formed with
the classical alkyl/aryl functionalized dithiocarbamate ligands [11].
Recently we modified the dithiocarbamate backbone by intro-
ducing the pyridyl group which resulted in the formation of both
inter- and intramolecular MꢁN bonding/bonding interactions in
* Corresponding author. Fax: þ91 542 2386127.
E-mail addresses: nsinghbhu@gmail.com, nsingh@bhu.ac.in (N. Singh).
http://dx.doi.org/10.1016/j.jorganchem.2015.03.034
0022-328X/© 2015 Elsevier B.V. All rights reserved.

66
A.N. Gupta et al. / Journal of Organometallic Chemistry 787 (2015) 65e72
Experimental section
R
R
S
S
S
S
R
S
S
N
N
N
Materials and methods
R'
R'
R'
All experiments were performed in open atmosphere. The
chemicals 4-ethoxycarbonylpiperidine (SigmaeAldrich), pyridine-
4-aldehyde, pyridine-3-aldehyde, 3-picolylamine, benzyl amine
and N-phenylpiperazine (all SPECTROCHEM) were used as
received. Solvents were distilled prior to use. The potassium salt of
the ligands (4-phenylpiperazine-1-dithiocarbamate) KL1, (N-
benzyl-N0-methyl-4-pyridyldithiocarbamate) KL2, (N-benzyl-
N0-methyl-3-pyridyldithiocarbamate) KL3, N, N0-di(methyl-3-
lpyridyl)dithiocarbamate KL4 and 4-ethoxycarbonylpiperidine-1-
dithiocarbamate KL5 were prepared by reaction of appropriate
secondary amines with KOH and CS2 in THF according to previously
reported procedures [12] and characterized by IR, 1H and 13C NMR
spectra. The experimental details pertaining to elemental (C, H, N)
analyses, IR (KBr discs), NMR (1H,13C and 119Sn), UVeVis. absorption
and photoluminescent spectra are the same as described elsewhere
[12]. TGA was recorded on a Perkin Elmer STV 6000 TG/DTA.
b
a
c
Fig. 1. Resonance structures of the dithiocarbamate ligands.
homo- and heteroleptic complexes which showed strong lumines-
centcharacteristics [12]. Thepyridyl functionalizeddithiocarbamate
ligands manifest several features such as (i) the far apart Py(N) and
dithiocarbamate (S,S) donor atoms may facilitate polymeric struc-
tures via MꢁN bonding/bonding interactions in homo- and heter-
ometallic complexes (ii) the enhanced conjugation and
conformational rigidity provided by the Py(N) may modify the
luminescent behaviour of the complexes and (iii) the Py(N) makes
available the bonding sites that may facilitate intra- and intermo-
lecular hydrogen bonding to generate multidimensional arrays
which are obviously not associated with the common alkyl/aryl di-
thiocarbamates. These modifications to the ligand environment can
lead to significant changes in the structures (Fig. 2), luminescent
properties and their uses as single source precursor for tin sulphides.
Syntheses of complexes
[R2SnL2] (R ¼ nBu, L ¼ L1, 1; L2, 2; Ph, L3, 3)
N
C
N
C
[R3SnL] (R ¼ Ph, L ¼ L4, 4; L5, 5)
The complexes 1e3 were prepared by treating the one equiva-
lent methanolic solution of the dibutyltin dichloride (0.303 g,
1 mmol)/diphenyltin dichloride (0.343 g, 1 mmol) with two
equivalents of respective ligands while 4 and 5 were prepared by
treating the triphenyltin chloride (0.385 g, 1 mmol) with the
respective ligands in 1:1 ratio as given in Scheme 1b. The white
precipitate was formed in a little while. In each case the reaction
mixture was stirred for 6 h and the solid product was collected by
filtration, washed with MeOH (2 ꢂ 5 ml) and ether (5 ml), and
vacuum-dried. The crude products were recrystallized from
dichloromethane/methanol mixture, yielding white crystals of the
compounds 1e5.
N
N
N
N
S
S
S
S
Sn
Ph Sn
Ph
Sn
Ph
Ph
Ph
N
Ph
(i)
(ii)
Fig. 2. The possible coordination modes for the pyridine functionalized ligand L4.
In order to establish possible changes in bonding behaviour/
molecular architectures and luminescent characteristics it was
considered worthwhile to make changes to the ligand frameworks
and to undertake the synthesis, structural investigations, lumi-
nescent properties and TGA of five new organotin(IV) complexes
utilizing the 4-phenylpiperazine-1-dithiocarbamate L1, N-benzyl-
N0-methyl-4-pyridyldithiocarbamate L2, N-benzyl-N0-methyl-3-
pyridyldithiocarbamate L3, N,N0-dimethyl-3-pyridyldithiocarba
mate L4 and 4-ethoxycarbonylpiperidine-1-dithiocarbamate L5 li-
gands (Fig. 3). The results of these investigations are described in
this presentation.
Characterization data
[(nBu)2Sn(L1)2] (1): Yield: (0.459 g, 75%), m. p. 140e142 ꢀC.
Anal. calc. for C30H44N4S4Sn (707.62): C, 54.46; H, 6.57; N, 3.97%.
Found: C, 54.35; H, 6.39; N, 3.78%. IR (KBr, cmꢁ1
)
d
n
¼ 1466 (nC‒N),
1077 (nC‒S) cmꢁ1. 1H NMR (300.40 MHz, CDCl3):
¼ 7.24e6.84 (m,
10H, C6H5ꢁ), 4.19 (s, 8H, C2H4-NPh), 3.22 (s, 8H, C2H4eNCS2), 1.99
(broad, 2H, eCH2), 1.83 (broad, 2H, eCH2), 1.40e1.33 (m, 2H, eCH2),
0.86 (t, J ¼ 7.2 Hz, 3H, eCH3) ppm. 13C NMR (75.45 MHz, CDCl3):
0
d
¼ 200.66 (CS2), 150.26 (1C, NeC1 of C6H5eN),129.29 (2C, C3 & C3 ),
0
120.59 (1C, C4), 116.43 (2C, C2 & C2 ), 50.84, 48.80 (NC4H8-NPh),
29.66 (C-
a
), 28.42 (C-
b
), 26.37 (C-
g
), 13.78 (C-
d
) (C4H9Sn) ppm,
¼ ꢁ330.66 ppm.
(C4H9Sn) ppm. 119Sn NMR (111.95 MHz, CDCl3):
d
UVevis. (CH2Cl2, lmax/nm, Ɛ/Mꢁ1 cmꢁ1): 258 (7.45 ꢂ 104), 290
(2.93 ꢂ 104).
[(nBu)2Sn(L2)2] (2): Yield: (0.537 g, 69%) m. p. 154e157 ꢀC. Anal.
calc. for C36H44N4S4Sn (779.6): C, 55.45; H, 5.69; N, 7.19%. Found: C,
55.28; H, 5.51; N, 6.96%. IR (KBr, cmꢁ1
)
n
¼ 1483 (nC‒N), 1080 (nC‒S
)
cmꢁ1. 1H NMR (300.40 MHz, CDCl3):
d 8.58 (s, 4H, Py-H), 7.32e7.11
(m, 14H, Py-H þ AreH) 4.94 (s, 4H, Py-CH2), 4.89 (s, 4H, AreCH2e),
1.87 (broad, 2H, eCH2), 1.73 (broad, 2H, eCH2), 1.46e1.39 (m, 2H,
eCH2), 0.93 (t, J ¼ 7.2 Hz, 3H, eCH3) ppm. 13C NMR (75.45 MHz,
CDCl3):
d
¼ 201.82 (CS2), 150.19, 143.02, 133.32, 128.75, 122.12
(C5H5N þ C6H5), 57.74 (Py-CH2), 55.27 (ArCH2), 29.33 (C-
a), 27.82
(C- ), 26.14 (C- ), 13.64 (C-
b
g
d)
(C4H9Sn) ppm. 119Sn NMR
(111.95 MHz, CDCl3):
d
¼ ꢁ336.82 ppm. UVevis. (CH2Cl2, lmax/nm,
Ɛ/Mꢁ1 cmꢁ1): 255 (5.11 ꢂ 104), 286 (2.0 ꢂ 104).
Fig. 3. Structure of the ligands (KL1-KL5) used in this work.

A.N. Gupta et al. / Journal of Organometallic Chemistry 787 (2015) 65e72
67
[Ph2Sn(L3)2] (3): Yield: (0.622 g, 76%) m. p. 159e162 ꢀC. Anal.
calc. for C40H36N4S4Sn (819.6): C, 58.61; H, 4.43; N 6.83%. Found: C,
dichloride in 2:1 ratio while 4 and 5 by the reaction between KL4
or KL5 and triphenyltin(IV) chloride in 1:1 ratio (Scheme 1). All the
complexes are isolated in quantitative yields, air stable, soluble in
most common organic solvents and melt in temperature range
140e178 ꢀC.
58.46; H, 4.28; N 6.62%. IR (KBr, cmꢁ1
)
n
d
¼ 1469 (nC‒N), 1069 (nC‒S
)
cmꢁ1 .1H NMR (300.40 MHz, CDCl3):
¼ 8.54e8.43 (m, 4H, Py),
7.65e7.19 (m, 14H, AreH þ PyH), 4.98 (s, 4H,eCH2ꢁ) ppm. 13C NMR
(75.45 MHz, CDCl3):
d
¼ 202.97 (CS2), 150.24, 149.54, 135.48, 134.25,
133.60, 130.57, 128.65, 123.73 (C5H5Nþ(C6H5)2Sn) ppm. 119Sn NMR
(111.95 MHz, CDCl3):
d
¼ ꢁ483.31 ppm. UVevis. (CH2Cl2, lmax/nm,
Ɛ/Mꢁ1 cmꢁ1): 258 (5.91 ꢂ 104), 295 (1.6 ꢂ 104).
[Ph3SnL4] (4): Yield (0.449 g, 72%) m. p. 176e178 ꢀC. Anal. calc.
for C31H27N3S2Sn (624.3): C, 59.73; H, 4.36; N, 6.73%. Found: C,
59.58; H, 4.53; N, 6.58%. IR (KBr, cmꢁ1
)
n
¼ 1479 (nC‒N), 1070 (nC‒S
¼ 8.55e8.48 (d, 2H, C5H5N)
7.26e7.82 (m, 18H, AreHþ3H, C5H5N), 5.07 (s, 4H, PyeCH2e) ppm.
13C NMR (75.45 MHz, CDCl3):
)
Scheme 1. General methodology for the synthesis of complexes 1e5.
cmꢁ1. 1H NMR (300.40 MHz, CDCl3):
d
Spectroscopy
d
¼ 200.55 (CS2), 149.54, 148.99,
141.24, 123.77 (C5H5N), 136.41, 135.45, 130.44, 129.38, 128.65,
IR spectra of the complexes 1e5 show n(CeN) and n(CS2) fre-
128.45 (SnC6H5) ppm. 119Sn NMR (111.95 MHz, CDCl3):
quencies near 1466e1483, and 1069e1080 cmꢁ1 diagnostic of
dithiocarbamate ligand coordination. A significant enhancement in
d
¼ ꢁ162.75 ppm. UVevis. (CH2Cl2, lmax/nm, Ɛ/Mꢁ1 cmꢁ1): 256
(9.03 ꢂ 104), 300 (2.42 ꢂ 104).
the n(CeN) frequency of the dithiocarbamate complexes in com-
[Ph3SnL5] (5): Yield: (0.500 g, 80%) m. p. 149e151 ꢀC. Anal. calc.
for C27H29NO2S2Sn (582.3): C, 55.68; H, 5.02; N, 2.41%. Found: C,
parison to the potassium salts of the ligands KL1-KL5
(1259e1348 cmꢁ1) concomitant with an increase in the CeN bond
order (vide infra, X-ray crystallography) and dominant resonance
structure (Fig. 1c).
55.52%, H, 4.83; N, 2.19%. IR (KBr, cmꢁ1
)
n
¼ 1477 (nC‒N), 1069 (nC‒S
)
cmꢁ1. 1H NMR (300.40 MHz, CDCl3):
d 7.79e7.36 (15H, (C6H5)3Sn),
4.18e4.11 (q, 2H, eOeCH2ꢁMe), 3.49e3.42 (t, 4H, eN(CH2)2e), 2.66
In 1H NMR spectra of the complexes (1e5), show characteristic
resonances of the ligand functionalities and integrate well to the
corresponding hydrogen atoms and there is no perceptible shift in
the proton NMR spectra of complexes in comparison to the po-
tassium salts of the ligands. In the 13C NMR all the complexes
showed a single low field resonance associated with the NCS2
carbons of the dithiocarbamate moieties in the range
(s, 1H, CHeCOOEt), 2.0e2.03 (m, 4H, CH(CH2)2), 1.27e1.22 (t, 3H,
CH3ꢁ) ppm. 13C{1H} (75.45 MHz, CDCl3):
d 195.58 (CS2), 173.72
(eCOOEt), 142.15, 136.41, 135.45, 130.29, 129.64, 128.83, 128.45
(SnC6H5) 60.79 (eCH2), 51.80, 50.55 (N(CH2)4), 39.31 (C(CH2)2),
27.69 (CH), 14.06 (CH3ꢁ) ppm. 119Sn NMR (111.95 MHz, CDCl3):
d
¼ ꢁ183.40 ppm. UVevis. (CH2Cl2, lmax/nm, Ɛ/Mꢁ1 cmꢁ1): 250
(9.82 ꢂ 104), 300 (2.83 ꢂ 104).
d
195.58e202.97 ppm. Notably because of the dominant contribu-
tion of R2Nþ¼CS22¡ resonance form in the dithiocarbamate com-
plexes the NCS2 carbon is more shielded than the free ligands hence
the 13C signal is shifted to higher field in the complexes as
Crystallography and theoretical calculations
X-ray crystal structure determinations
compared to free ligands (
d
¼ 213.62e214.75 ppm).
119Sn NMR spectroscopy is a very useful tool for investigating
the coordination environment about the tin atom in organotin
dithio complexes. As the coordination number around the tin in-
creases, the 119Sn chemical shift moves to lower frequency
depending on the nature of substituents present on the dithio
backbone. The 119Sn NMR chemical shifts for the di-n-butyltin de-
The X-ray diffraction data were collected by mounting single
crystals of the samples on glass fibers. Single crystal X-ray data for
1e5 were collected on an Oxford Diffraction X-calibur CCD
diffractometer at 293 K using Mo Ka radiation. The CRYSALIS pro-
gram was used for data reduction [14a]. The crystal structures were
solved by direct methods using the SHELXS-97 program [14b] and
refined on F2 by full matrix least-squares technique using SHELXL-
97 [14c]. All non-hydrogen atoms were refined anisotropically and
hydrogen atoms were geometrically fixed. In complex 4, there are
two molecules called A and B in the asymmetric unit. In A, nitrogen
atom in a pyridine rings is disordered over two sites. Molecular
structures were drawn using Diamond 3.0 and their weak in-
teractions were shown using Mercury 2.2.
rivatives 1 and 2 are
typical of six coordination of the tin atom while for diphenyltin
derivative (3)
d
ꢁ330.66 and ꢁ336.82 ppm respectively are
d
ꢁ483.31 ppm is well within the range of dio-
rganotin dithiocarbamates. The triphenyltin derivative 4 and 5
show chemical shifts ꢁ162.75 and ꢁ183.40 ppm respectively which
is diagnostic of the five coordinate tin complexes [11b,h].
UVeVis. and photoluminescent spectra
Theoretical calculations
The UVeVis. absorption spectra of 1e5 (Fig. 4a) in the
Single point calculations were carried out using the Gaussian 03
program [15] Structures were optimized using the B3LYP density
functional together with basis sets LANL2DZ for Sn, 6-31þG* for S
and 6-31G for the remaining atoms. Starting models were taken
from the crystal structures but with hydrogen atoms given theo-
retical positions.
dichloromethane solution display strong to medium bands near
260 nm (Ɛ
¼
51,110e98,200 Mꢁ1 cmꢁ1
)
and 300 nm
(Ɛ ¼ 16,000e29,300 Mꢁ1 cmꢁ1) which are assignable to
p-
p*intraligand charge transfer (ILCT) and ligand to metal charge
transfer (LMCT) transitions respectively [11e].
In comparision to main group metal complexes, the luminescent
properties of tin(IV)/organotin(IV) are extremely rare in the liter-
ature. Upon excitation at 285e300 nm the all the complexes except
1 exhibits a broad unstructured emission band at about 400 nm
(Fig. 4b) which emanates from the LMCT state. It is worth
mentioning that the lone pair of electrons on the pyridyl func-
tionalities in 4 enhances conjugation, thus increasing the lumi-
nescent character in comparison to 2 and 3 with only one pyridyl
Results and discussion
Synthetic procedure
The complexes 1e3 were synthesized by the reaction between
the respective ligand (Fig. 3) and di-n-butyl/diphenyltin(IV)

68
A.N. Gupta et al. / Journal of Organometallic Chemistry 787 (2015) 65e72
Table 1
Selected bond lengths (Å) and bond anglesꢀ for 1e3.
1
2
3
Sn(1)eS(11)
Sn(1)eS(13)
Sn(1)-C(41)
S(11)eC(12)
S(13)eC(12)
C(12)eN(14)
S(13)eSn(1)eC(41)
C(41)eSn(1)eC(41a)
S(13)eSn(1)eS(13a)
C(41)-Sn(1)-S(13a)
C(41)-Sn(1)-S(11)
C(41)-Sn(1)-S(11a)
S(11)-Sn(1)-S(13)
S(13)-Sn(1)-S(11a)
S(11)-Sn(1)-S(11a)
S(11)eC(12)eS(13)
2.9714(6)
2.5332(6)
2.140(2)
1.695(2)
1.731(2)
1.340(3)
103.91(7)
140.7(1)
84.79(3)
104.88(7)
84.60(8)
84.05(8)
64.71(3)
149.49(3)
145.80(3)
120.09(13)
2.8960(13)
2.5543(12)
2.145(5)
1.705(5)
1.728(5)
1.356(6)
104.27(14)
141.4(3)
2.5932(12)
2.6798(13)
2.139(4)
1.724(4)
1.713(4)
1.334(5)
159.63(12)
101.9(2)
87.81(6)
77.25(5)
103.30(13)
81.44(13)
85.69(14)
65.95(4)
153.58(4)
140.41(5)
120.5(3)
92.68(12)
94.86(11)
101.48(11)
68.07(4)
91.23(4)
153.96(4)
118.3(3)
a
Symmetry elements 1 -x, y, 1.5-z; 2 1-x, y, 1.5-z; 3 1-x, y, 0.5-z.
and 4.05ꢀ in 2 so could be described as forming an equatorial plane.
However the C41eSneC41 angles are far from axial being 140.7(1)ꢀ
and 141.4(3)ꢀ. The coordination geometry around the tin atom is
best considered as six-co-ordinate with a severely distorted octa-
hedral geometry. In 3, the geometry around the tin atom is very
different. The two independent SneS distances are similar with
SneS11, SneS13 2.593(1) and 2.680(1) Å. The SneC41 bond length
is 2.139(4) Å. The two four-membered chelating dithiocarbamate
rings intersect at 87.6(1)o and the geometry can be described as a
distorted octahedral with three sulphur atoms and one carbon
atom in the equatorial plane [11f]. The angle C41eSneC41 is
101.9(2)ꢀ, c.a. 40ꢀ less than the values in 1 and 2.
The more intriguing feature of 3 is the supramolecular structure
sustained by the intermolecular CeH/N non-classical hydrogen
bonding interactions between N(36) and C(37)-H across the centre
of symmetry at (1/4, ꢁ1/4, 0) which extends in 1-D chain and sta-
bilized by the 6-membered cyclic structure analogue of benzene
(Fig. 6) with dimensions N…H (2.63 Å), C/N (3.473 Å) and angle
CeH/N (152ꢀ). DFT calculations on two molecules interacting in
this way gave an energy of 8.54 kcalmolꢁ1 less than the energy of
two separated molecules showing that the interaction is a very
significant part of the molecular packing.
Fig. 4. (a) UVeVis. absorption spectra of 1e5 in CH2Cl2 solution and (b) Photo-
luminescent spectra of 1e5 at room temperature.
group. Also, 5 shows somewhat strong luminescent behaviour due
to two phenyl groups bonded to the tin thereby increasing the
conjugation over the molecule in comparison to 1 having di-n-
butyl fragment.
Crystal structures
Table 2
Selected bond lengths (Å) and bond anglesꢀ for 4A, 4B and 5.
Single crystals of 1e5 were grown by slow evaporation of the
dichloromethane/methanol solution of the compounds. Selected
bond distances, bond angles and crystallographic details are listed
in Tables 1 and 2 and Table S1, ESI and molecular diagrams for 1e5
are shown in Figs. 5 and 7.
4A
4B
5
Sn(1)eS(11)
Sn(1)eS(13)
S(11)eC(12)
S(13)eC(12)
C(12)eN(14)
Sn(1)-C(41)
Sn(1)-C(51)
Sn(1)-C(61)
Sn(1)eS(11)eC(12)
S(11)eC(12)eS(13)
S(11)-Sn(1)-S(13)
S(11)eSn(1)eC(41)
S(11)eSn(1)eC(51)
S(11)eSn(1)eC(61)
C(41)eSn(1)eC(51)
C(41)-Sn(1)-C(61)
C(51)-Sn(1)-C(61)
S(13)-Sn(1)-C(41)
S(13)-Sn(1)-C(51)
S(13)-Sn(1)-C(61)
2.469(2)
3.040(2)
1.747(6)
1.696(6)
1.325(7)
2.152(7)
2.138(7)
2.129(6)
97.5(2)
118.7(4)
61.0(1)
91.5(2)
117.1(2)
116.1(2)
104.1(3)
107.2(3)
116.1(3)
155.6(2)
87.9(2)
2.516(2)
3.221(2)
1.756(6)
1.665(7)
1.352(7)
2.151(7)
2.120(6)
2.121(6)
100.0(2)
120.7(4)
64.1(1)
2.467(1)
3.021(1)
1.753(3)
1.685(3)
1.330(4)
2.170(3)
2.143(3)
2.149(3)
96.64(11)
118.87(18)
64.38(6)
93.7(1)
116.7(1)
117.4(1)
105.7(1)
104.7(1)
114.6(1)
157.8(1)
88.4(1)
In the crystal structures of 1, 2 and 3 the metal occupies a two-
fold axis so that the asymmetric unit contains only half of the
molecule. In each case, the metal is bonded to sulphur atoms from
two dithiocarbamate ligands and two carbon atoms from c.a. di-n-
butyl (in 1, 2) or phenyl ligands (in 3). In 1 and 2, the sulphur atoms
of the dithiocarbamate ligands are bound unequally to the tin atom
with S11 at distances 2.533(1)e2.554(1) Å and the S13 at somewhat
longer distances of 2.896(1)e2.971(1) Å although these latter dis-
tances are still significantly less than the sum of the van der Waals
radii of tin and sulphur (3.97 Å) and can be considered as bonds.
The SneC distances of 2.140(2)e2.145(5) Å in these complexes are
well within the range of reported diorganotin(IV) dithiocarbamate
complexes [11a,b,d]. The two four-membered dithiocarbamate
chelate rings are almost coplanar intersecting at angles of 1.95ꢀ in 1
92.0(2)
105.0(2)
108.7(2)
111.2(3)
108.6(2)
125.9(3)
153.0(2)
78.0(2)
85.5(2)
82.9(2)
83.9(1)

A.N. Gupta et al. / Journal of Organometallic Chemistry 787 (2015) 65e72
69
Fig. 5. Molecular structure and atom numbering scheme for 1, 2 and 3, Color code: Sn, Turquoise blue; S, Orange; N, Ink blue; C, Grey; H, Grey (Small). (For interpretation of the
references to colour in this figure legend, the reader is referred to the web version of this article.)
The structures of 4 and 5 are similar with the tin atom is
bonded asymmetrically to one bidentate dithiocarbamate ligand
and three phenyl groups. The asymmetric unit of 4 contains two
molecules 4A and 4B. In both structures the metal atom forms a
short bond to S11 (2.469(2), 2.516(2), 2.467(1) Å) and a longer
bond to S13 at 3.040(2), 3.221(2), 3.021(2) Å in 4A, 4B, 5
respectively. The SneC bonds range from 2.120(6)e2.170(3) Å
which are well within the range of analogous triorganotin(IV)
dithiocarbamate complexes [11a,h]. If the longer SneS13 bond is
considered as a bond, then the overall coordination geometry
around the tin atom is five-coordinate trigonal bipyramidal with
a phenyl group C51 and S13 in axial positions. This is confirmed
by the
t values which are 0.57, 0.58, 0.65 for 4A, 4B and 5
respectively.
Fig. 6. N/HeC interactions forming a cyclic structure in 1-D chain motifs in 3.

70
A.N. Gupta et al. / Journal of Organometallic Chemistry 787 (2015) 65e72
Fig. 7. Molecular structure and atom numbering scheme for (a) 4A and (b) 5. Color code: Sn, Turquoise blue; S, Orange; N, Ink blue; C, Grey; H, Grey (Small). (For interpretation of
the references to colour in this figure legend, the reader is referred to the web version of this article.)
More interestingly in 4B, (but not in 4A) the pyridyl(N) on an
adjacent molecule is bonded to tin at somewhat longer distance of
3.116(8) Å which is less than sum of the van der Waals radii of tin
and nitrogen which is 3.72 Å resulting in the formation of 1-D
polymeric chain motif. It should be noted however that this dis-
tance is ca. 1.0 Å longer than the SneC (phenyl) distances. The
overall geometry about the Sn atom can then be considered as
distorted octahedral with rare coordination of (3Cþ2Sþ1N) (Fig. 8).
Theoretical calculations were carried out on both molecules (A and
complexes the values of
d between 2.4 and 3.6 Å were crucial to assesses the interactions
where is the angle between the perpendicular to the ring and the
CG/H vector, , the CG/HeC angle and d, the CG/H distance. The
a < 20, b
ranging from 110 to 180ꢀ and
a
b
interaction between H34B (1þx, y, z) and the SnS2C ring of mole-
cule A is well within the usual limits. The H34B/CG distance is
2.85 Å, with a, 1.7 and b
is 146.9ꢀ (Fig. 9) despite the asymmetric
bonding of the dithio ligand. However the energy difference be-
tween the two molecules interacting in this way (A þ B) and the
separate molecules is negligible. Thus the energy gained by the
H/CG interaction is cancelled out by poor steric effects involving
the 3 phenyl rings. The calculation was then repeated but with the
phenyl rings then replaced with methyl groups. Now the energy
difference was ꢁ1.58 kcalmolꢁ1 which supports the view that the
interaction of the phenyl rings is repulsive and cancels out the ef-
fect of the interaction between H34B and the SnS2C ring.
B) in 4, and it was found that B is more stable by 2.16 kcalmolꢁ1
,
when the additional SneN bond found in B is not considered. For
molecule B, the dimer with two B molecules connected by the
SneN36 (x, 1þy, z) bond at 3.116(8) Å is more stable than two
separate monomers by 9.76 kcalmolꢁ1, thus confirming that the
SneN interaction is significant.
Recently Tiekink and Zukerman-Schpector [13] evaluated the
structural characteristics of CeH-
CeH bonds and the centroid CG of four-membered MS2C chelate
ring in metal bis(1,1-dithiolates). For homoleptic bisedithio
p
(chelate) interactions between
The closest S/S intermolecular distances between the coordi-
nated dithiocarbamate ligands in 1e5 fall in the 4.14e6.76 Å range
and are significantly larger than van der Waals radii so that there is
Fig. 8. (a) Polymeric 1-D chain motifs in 4 through intermolecular Sn/N secondary interactions (b) S2C3N coordination pattern around the tin centre.

A.N. Gupta et al. / Journal of Organometallic Chemistry 787 (2015) 65e72
71
CeH/CG interactions between the two molecules. To our knowl-
edge 3 and 4 are the examples of organotin dithiocarbamate
complexes delineating these rare interactions. These have been
supported by theoretical calculations. Except 1 all the complexes
showed moderate to strong luminescent characteristics in CH2Cl2
solution at room temperature originating from the LMCT state.
Complex 4 containing two pyridyl groups showed strong lumi-
nescent characteristics due to rich electron cloud on the molecules
and providing overall conformational rigidity an important pre-
requisite for the higher luminescent behaviour of the molecules.
TGA of 3 and 5 showed double and single step decomposition
leaving residue corresponding to SnS2 and SnS respectively. This
study demonstrates that the organotin complexes with these un-
derexploited dithiocarbamate ligands may be useful as functional
materials.
Acknowledgements
The Council of Scientific and Industrial Research (CSIR), Project
No. 01(2679)/12/EMR-II (NS), Science and Engineering Research
Board (SERB, SB/SI/IC-15/2014), University Grants Commission
(ANG) SRF, New Delhi and the Department of Chemistry, Banaras
Hindu University, Varanasi INDIA for the Oxford diffraction X-cal-
ibur CCD diffractometer used for the structure determinations are
gratefully acknowledged.
Fig. 9. Nearest intermolecular CeH/CG (SnS2C) interactions between CG of unit 4A
and H34B of unit 4B.
no significant S/S intermolecular associations in these complexes.
In all the complexes the supramolecular architectures are stabilized
via weaker S/H non-covalent interactions. The C(12)eN(14) dis-
tances of 1.325(7)e1.356(6) Å in 1e5 are concomitant with the
resonance structure (Fig. 1). In all the complexes the length of the
CeS bond is inversely correlated with the SneS bond, thus short
SeC bonds of 1.665(7)e1.705(5) Å and long SeC bonds of 1.728(5)e
1.756(6) Å correlate with long and short SneS bonds respectively.
The exception is 3, where the similar SneS bond lengths are
accompanied by similar SeC bond lengths, 1.713(4), 1.723(4) Å
though all are significantly shorter than the CeS single bond
Appendix A. Supplementary data
CCDC 1017534 (1), 1017533 (2), 1017535 (3) 1017536 (4) and
1017532 (5) contain the supplementary crystallographic data for
this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data centre via www.ccdc.cam.ac.uk/
data_request/cif.
Appendix B. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jorganchem.2015.03.034.
(ca.1.81 Å) due to
p delocalization over the NCS2 units.
Thermogravimetric analysis (TGA)
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