Synthesis, spectroscopic and structural characterization of diphenyltin(IV) complexes of acetone Schiff bases of S-alkyldithiocarbazates

Article abstract of DOI:10.1016/j.poly.2007.11.030

New diphenyltin(IV) complexes of empirical formula, [Sn(C₆H₅)₂(NS)Cl] (NS = anionic forms of the acetone Schiff bases of S-methyl or S-benzyldithiocarbazate) have been prepared and characterized by IR, NMR and M?ssbauer spectroscopic techniques. The crystal and molecular structures of the acetone Schiff bases of S-methyldithiocarbazate (Hacsme) and S-benzyldithiocarbazate (Hacsbz) and their tin(IV) complexes have been determined by X-ray diffraction. In the solid state, both the Schiff bases exist in their thioketo tautomeric forms with the azomethine nitrogen atom trans to the thione sulfur atom but in the tin(IV) complexes they are present in their deprotonated ene-thiolate forms being coordinated to the tin atom as bidentate chelating agents via the azomethine nitrogen and thiolate sulfur atoms. The tin atom adopts a five-coordinate, approximately trigonal bipyramidal geometry, with the thiolate sulfur atom of the Schiff base and the two phenyl groups occupying the equatorial positions. The azomethine nitrogen atom and the chlorine ligand occupy axial positions. The distortion from a regular trigonal bipyramidal or a square-pyramidal geometry is attributed to the restricted bite sizes of the five-membered chelate rings.

Full text of DOI:10.1016/j.poly.2007.11.030

Available online at www.sciencedirect.com
Polyhedron 27 (2008) 977–984
www.elsevier.com/locate/poly
Synthesis, spectroscopic and structural characterization
of diphenyltin(IV) complexes of acetone Schiff bases
of S-alkyldithiocarbazates
a,
a
a
*
Mohammad Akbar Ali , Aminul Huq Mirza , Malai Haniti S.A. Hamid ,
Paul V. Bernhardt b, Olaniran Atchade c, Xueqing Song c, George Eng c, Leopold May d
a Department of Chemistry, Universiti Brunei Darussalam, Jalan Tungku Link, Negara Brunei Darussalam BE1410, Brunei Darussalam
b Department of Chemistry, The University of Queensland, Brisbane 4072, Australia
c Department of Chemistry and Physics, University of the District of Columbia, Washington, DC 20008, USA
d Department of Chemistry, The Catholic University of America, Washington, DC 20064, USA
Received 22 August 2007; accepted 26 November 2007
Available online 11 January 2008
Abstract
New diphenyltin(IV) complexes of empirical formula, [Sn(C6H5)2(NS)Cl] (NS = anionic forms of the acetone Schiff bases of S-methyl
or S-benzyldithiocarbazate) have been prepared and characterized by IR, NMR and Mo¨ssbauer spectroscopic techniques. The crystal
and molecular structures of the acetone Schiff bases of S-methyldithiocarbazate (Hacsme) and S-benzyldithiocarbazate (Hacsbz) and
their tin(IV) complexes have been determined by X-ray diffraction. In the solid state, both the Schiff bases exist in their thioketo tauto-
meric forms with the azomethine nitrogen atom trans to the thione sulfur atom but in the tin(IV) complexes they are present in their
deprotonated ene-thiolate forms being coordinated to the tin atom as bidentate chelating agents via the azomethine nitrogen and thiolate
sulfur atoms. The tin atom adopts a five-coordinate, approximately trigonal bipyramidal geometry, with the thiolate sulfur atom of the
Schiff base and the two phenyl groups occupying the equatorial positions. The azomethine nitrogen atom and the chlorine ligand occupy
axial positions. The distortion from a regular trigonal bipyramidal or a square-pyramidal geometry is attributed to the restricted bite
sizes of the five-membered chelate rings.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Acetone Schiff bases of S-methyl- and S-benzyldithiocarbazate; Diphenyltin(IV) complexes; Oganotin complexes of dithiocarbazates
1. Introduction
complexes some of which have been shown to exhibit inter-
esting physico-chemical properties [11] and potentially use-
ful pharmacological activities [1,10,12]. As an example, the
palladium(II) complex of the acetone Schiff base of S-
methyldithiocarbazate (Hacsme) has been shown to exhibit
cytotoxic activity in the 9KB test system – a human epider-
moid carcinoma of the nasopharynx [13]. The palla-
dium(II) complex has also been found to display
cytotoxic activity against T-lymphoblastic leukemia cancer
cells [14]. There are also several other examples where
Schiff bases derived from S-alkyl esters of dithiocarbazic
acid and some of their metal complexes have been shown
to display antifungal and antibacterial properties [15].
Schiff bases derived from S-alkyl esters of dithiocarbazic
acid comprise an important class of sulfur–nitrogen chelat-
ing agents containing both soft sulfur and intermediate
nitrogen donor atoms in their structural backbones by vir-
tue of which they are capable of reacting with both transi-
tion and some main group metal ions [1–10] forming stable
*
Corresponding author. Tel.: +673 2 2463001x1341; fax: +673 2
461502.
E-mail address: akbar@fos.ubd.edu.bn (M.A. Ali).
0277-5387/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.11.030

978
M.A. Ali et al. / Polyhedron 27 (2008) 977–984
Although a large amount of work on the synthesis and
night. The product that had formed was filtered off, washed
with abs. ethanol and dried in a vacuum desiccator over
anhydrous silica gel. These compounds as isolated were
suitable for X-ray work. Yield: 50–60%. Compound 3
Sn(acsme)Ph2Cl: Anal. Calc. for C17H19N2S2ClSn: C,
43.48; H, 4.08; N, 5.96. Found: C, 43.40; H, 4.03; N,
5.85%. Compound 4 Sn(acsbz)Ph2Cl: Anal. Calc. for
C23H23N2S2ClSn: C, 50.62; H, 4.25; N, 5.13. Found: C,
50.52; H, 4.15; N, 5.46%.
characterization of transition metal complexes of Schiff
bases of S-alkyl esters of dithiocarbazic acid have been
reported [1–15] very little work has been reported on orga-
nometallic complexes of these ligands. In view of very little
information available on organotin(IV) complexes of dith-
iocarbazates and as part of our ongoing work on metal
complexes of dithiocarbazic acid and its derivatives, we
report here the synthesis, characterization and X-ray crys-
tal and molecular structures of the acetone Schiff bases of
S-methyl- and S-benzyldithiocarbazate together with the
structures of their chlorodiphenyltin(IV) complexes.
2.5. Crystallography
Cell constants were determined by a least-squares fit to
the setting parameters of 25 independent reflections, mea-
sured on an Enraf-Nonius CAD 4 four-circle diffractome-
ter using graphite monochromated Mo Ka radiation
2. Experimental
2.1. Reagents
˚
(0.71073 A) and operating in the x À 2h mode within the
Chemicals and solvents used were of analytical reagent
grade and used without any further purification. Dichloro-
diphenyltin(IV) was purchased from the Aldrich Chemical
Company.
range 2 < 2h < 50°. Empirical absorption correction (w
scans) and data reduction were performed with the WINGX
[17] suite of programmes. The structures were solved by
direct methods with SHELX86 and refined by full-matrix
least-squares analysis with SHELXL97 [18]. Non-hydrogen
atoms were refined with anisotropic thermal parameters
whereas H-atoms were included at estimated positions
using a riding model. Drawings of each molecule were pro-
duced with ORTEP3 [19]. A summary of the crystal data,
structure solution and refinement parameters are given in
Table 1 and selected bond lengths appear in Table 6.
2.2. Physical measurements
Microanalyses for C, H & N were performed by the Ele-
mental Analysis Laboratory, National University of Singa-
pore, Singapore. Molar conductivity of ca. 10À3 M
solutions of the complexes in DMSO were measured by
means of a Jenway 4310 conductivity meter. The IR spectra
were measured as KBr discs on a Perkin–Elmer 2000 FT-
IR spectrometer and the electronic spectra were measured
as Nujol mulls on a Shimadzu MPC-3100 spectrophotom-
3. Results and discussion
The acetone Schiff bases of S-methyldithiocarbazate and
S-benzyldithiocarbazate have a thioamide (–NH–CS–)
functional group and consequently, in principle, they are
capable of existing either as the thione form (1a) or the
thiol form (1b) or as a mixture of both thione and thiol tau-
tomeric forms (Fig. 1). In the solid state it has been shown
that they exist in their thione forms since their IR spectra
exhibit the mNH band at ca. 3300 cmÀ1 and no mSH band
at ca. 2600 cmÀ1 [14]. However, in solution they might exist
as an equilibrium mixture of both the thione and thiol tau-
1
eter. The H NMR spectra of the tin(IV) complexes were
run in CDCl3 on a Bruker DPX 300 MHz spectrometer
using TMS as an internal standard. The Mo¨ssbauer spectra
were recorded using a Model MS-900 (Ranger Scientific
Co., Burleson, TX) spectrometer in the acceleration mode
with moving source geometry. A 5-mCi Ca119mSnO3 source
was used. The spectra were measured at 80 K using a
liquid–nitrogen cryostat (CYRO Industries of America
Inc.). The velocity was calibrated at ambient temperature
using a composition of BaSnO3 and tin foil (splitting
2.52 mm sÀ1). The resultant spectra were analyzed by a
least-square fit to Lorentzian shaped lines.
1
tomeric forms. The H NMR spectra of the Schiff bases in
CDCl3 exhibit a signal at ca. 10.15 ppm which is character-
istic of an NH as opposed to an SH resonance. No signal at
ca. 4.00 ppm attributable to the SH proton was detected
indicating that even in solution they remain predominantly
as the thione tautomer.
2.3. Preparation of the ligands
The Schiff bases were prepared by following procedures
reported previously [14,16]. The compounds as isolated
from the reaction were suitable for X-ray crystallography.
3.1. Characterization of the Sn(IV) complexes
In a boiling ethanolic solution the Schiff bases react with
SnPh2Cl2 in their thiol tautomeric forms, deprotonate and
coordinate to the tin(IV)ion forming charge neutral com-
plexes of formula, SnPh2(NS)Cl (NS = deprotonated form
of the Schiff bases). The analogous acetone thiosemicarba-
zone which exhibits a structural backbone very similar to
the present compounds, has been shown to react with
2.4. General method of preparation of the complexes
To a solution of SnPh2Cl2 (1 mmol) in boiling abs. eth-
anol (70 ml) was added a solution of the appropriate Schiff
base (1 mmol) in the same solvent (70 ml) and the mixture
heated under reflux for 48 h and then left to stand over-

M.A. Ali et al. / Polyhedron 27 (2008) 977–984
979
Table 1
Crystallographic data
Hacsme (1)
Hacsbz (2)
Sn(acsme)Ph2Cl (3)
Sn(acsbz)Ph2Cl (4)
Empirical formula
Formula weight
T (K)
C5H10N2S2
162.27
293(2)
C11H14N2S2
238.36
293(2)
C17H19N2S2ClSn
469.60
293(2)
0.71073
orthorhombic
P21cn
9.535(2)
12.848(2)
16.493(2)
C23H23N2S2ClSn
545.69
293(2)
˚
k (A)
0.71073
monoclinic
P21/a
14.58(1)
11.653(4)
19.41(1)
98.58(6)
3261(3)
1.322
0.71073
monoclinic
P21/c
11.942(1)
6.163(7)
16.942(3)
94.77(1)
1242.2(3)
1.274
0.71073
monoclinic
P21/n
8.2242(9)
13.445(1)
22.187(3)
92.81(2)
2450.4(5)
1.479
Crystal system
Space group
˚
a (A)
˚
b (A)
˚
c (A)
b (°)
3
˚
V (A )
2020.5(6)
1.544
Dcalc (Mg/m3)
Z
16
0.573
1376
4
4
4
l (mmÀ1
F(000)
)
0.399
504
1.603
936
1.334
1096
Independent reflections [Rint
]
5702 [0.0523]
2538
5702/0/337
1.015
2173 [0.0323]
1040
2173/0/138
0.997
2121 [0]
1452
2121/1/198
0.993
4309 [0.0155]
3175
4309/0/265
1.020
Observed reflections (I > 2r(I))
Data/restraint/parameters
Goodness-of-fit on F2
R1 (observed data) and wR2 (all data)
0.0539 and 0.1668
0.0430 and 0.1188
0.0830 and 0.2503
0.0273 and 0.0722
conductance data confirm that the Schiff bases coordinate
to the tin atom in their monodeprotonated forms.
H3C
CH3
H3C
CH3
C
N
C
N
The IR spectra of the SnPh2(NS)Cl complexes when
compared with those of the free Schiff bases (Table 2) show
that the mNH bands of the free ligands at ca. 3300 cmÀ1 are
absent in the spectra of the complexes indicating that the
ligands are coordinated to the tin atom in their deproto-
nated mercaptide forms. The shift of the azomethine mC@N
H
S
N
C
N
C
RS
SH
RS
band in the IR spectra of the free ligands (1634–1628 cmÀ1
)
(1b; thiol form)
(1a; thione form; R = CH3, CH2Ph)
to lower wavenumber (1612–1608 cmÀ1) in the spectra of
complexes support coordination of the azomethine nitro-
gen atom to the tin atom. This is further supported by
the shift of the mN–N band of the free ligands to higher
wavenumbers in the spectra of the complexes.The elec-
tronic spectra of the complexes show the intraligand
n ? p* and p ? p* transitions in the ranges 363 and 311–
258 nm, respectively. The n ? p* band of the free ligands
is not affected in the electronic spectra of the complexes
but there is a hypsochromic shift of the p ? p* band upon
coordination to Sn(IV).
Fig. 1. The thione and thiol tautomeric forms of the Schiff base
(R = CH3, Hacsme; R = CH2Ph, Hacsbz).
SnPh2Cl2 yielding a diphenyltin(IV) complex containing
the neutral form of the ligand [20]. This example illustrates
the diversity of reactivity found in these Schiff base ligands
in their coordination chemistry with Sn(IV).
The complexes are stable at room temperature and may
be kept in a desiccator over anhydrous silica gel for
extended periods without any sign of decomposition. The
molar conductivities of Sn(acsme)Ph2Cl and Sn(acs-
bz)Ph2Cl in DMF are 11.7 and 11.8 XÀ1 cm2 molÀ1, respec-
tively, indicating that even in a polar coordinating solvent
like DMF, they behave essentially as non-electrolytes. The
1
The H NMR spectra of the complexes do not contain
the signal due to the NH proton of the free ligands at
10.15 ppm supporting further the IR evidence presented
earlier that the ligands are coordinated to the tin atom in
Table 2
IR and electronic spectra for the ligands and their diphenyltin(IV) chloride complexes
Compound
IR bands
Electronic spectrab kmax (nm)
mNH
mCN
mNN
mCSS
Hacsmea
ꢀ3300sh
ꢀ3300sh
1634
1064s
1069
1068m
1074m
998s
998s
1024, 997m
1011, 996m
364, 293
340, 298
363sh, 311
362sh, 325sh, 258
Hacsbza
1628s
1608s
1612s
[Sn(acsme)(C6H5)2Cl]
[Sn(acsbz)(C6H5)2Cl]
a
Data taken from Ref. [14].
Solid state (Nujol mull).
b

980
M.A. Ali et al. / Polyhedron 27 (2008) 977–984
their deprotonated thiolate forms. The 1H NMR spectra of
SnPh2(NS)Cl show two signals due to two acetone-derived
methyl groups due to restricted rotation about the C@N
bond. The methyl group, syn to the N–N bond resonates
at a higher field than the anti methyl group [21] (see Table
3).
scheme causes a reduction in the s-electron contribution
in the complexes relative to that of the starting tin com-
pound [23], thus decreasing the value of the isomer shift.
The q values, which are used to predict coordination
numbers of tin complexes, are found to be 2.02, support-
ing a coordination number greater than four for the tin
ion in the tin complexes [24].
The angle, h between the axial carbon atoms and tin
atom can be obtained from the Mo¨ssbauer spectrum
using the relationship, |D| = À4[R](1–0.75sin2 h)1/2 where
D is the observed quadrupole splitting, h is the R–Sn–R
angle in the complex and [R] is the partial quadrupole
splitting (PQS) of the axial groups [25]. The calculated
angle for Sn(acsme)Ph2Cl is 122.9° using [R] of À0.94
[26] and for Sn(acsbz)Ph2Cl, 127.3° using [R] of À0.89
[26]. This compares favorably with the values of the
angles found by X-ray crystallography; 122.9° and
127.1°, respectively.
The Mo¨ssbauer spectra of the Sn(NS)Ph2Cl complexes
are shown in Figs. 2 and 3 and the isomer shift (d), quad-
rupole splitting (D) and q values are given in Table 4.
The parameters (d and D) are within the range found
with Sn (IV) and organotin compounds [22]. The Mo¨ss-
bauer spectra of the tin complexes exhibit identical d
indicating that the substituents (methyl or phenyl) on
one of the sulfur atoms of the dithiocarbazate moiety
do not have any effect at all on the s-electron density
at the tin nucleus. The spectra of the two compounds
also exhibit the same values of D indicating that they
have the same structure. X-ray crystallographic structure
determination (see later) confirms this fact. The Mo¨ss-
bauer spectra of the present tin(IV) complexes have lower
d values than the starting tin compound, SnPh2Cl2
3.2. Crystal structures of the free ligands
(1.34 mm sÀ1
)
[23].
A
re-hybridization
in
the
The structures of Hacsme and Hacsbz are shown in
Figs. 4 and 5, respectively, and relevant bond lengths and
bond angles are given in Table 5. The asymmetric unit of
Hacsme has four crystallographically independent mole-
cules (referred to here as molecules A, B, C and D) which
have very similar bond lengths and bond angles. Molecule
[Sn(NS)Ph2Cl] complexes (due to higher coordination
number of the tin atom in the complexes relative to that
in SnPh2Cl2) accounts for the smaller isomer shift d
value. A greater involvement of the d orbitals in the tin
complexes, which take part in the re-hybridization
Table 3
1H and 13C NMR spectroscopic data
Compound
1H NMR assignments
13C NMR assignments
CH3(syn)
CH3(anti)
SCH3/SCHÀ2 NH
Ar
CH3(syn) CH3(anti) SCH3/SCHÀ2 CN
CS
152.73 200.62
ArC
Hacsme
Hacsbz
[1.96]a 1.95
(s, 3H)
[2.04]a 2.08
(s, 3H)
[2.57]a 2.62
(s, 3H)
9.78 (1H)
16.68
17.74
25.28
1.95 (s, 3H) 2.04 (s, 3H) 4.52 (s, 2H)
9.68 (1H)
7.28–7.32
16.79
25.24
39.48
152.81 198.93 127.43
(m, 2H) 7.40
(d, J = 8 Hz, 2H)
128.57
129.44
136.04
[Sn(acsme)
(C6H5)2Cl]
1.55 (s, 3H) 2.28 (s, 3H) 2.52 (s, 3H)
7.26 (m, 4H),
7.45 (m, 4H),
7.49 (m,2H)
14.92
23.01
22.92
25.67
25.65
36.34
143.67 174.31 129.09
130.02
134.51
134.90
[Sn(acsbz)
(C6H5)2Cl]
1.54 (s, 3H) 2.28 (s, 3H) 4.42 (s, 2H)
7.25–7.77
(m, 15H)
143.67 174.54 127.59
128.69
128.54
129.68
128.99
129.10
130.03
134.88
a
Data reported by [29].

M.A. Ali et al. / Polyhedron 27 (2008) 977–984
981
Fig. 4. ORTEP3 view of 1 Hacsme (only one of the four molecules (A) in the
asymmetric is shown with 30% probability ellipsoids).
Fig. 2. The Mo¨ssbauer spectrum of Sn(acsme)Ph2Cl.
Fig. 5. ORTEP3 view of 2 Hacsbz (30% probability ellipsoids).
Table 5
Selected bond lengths
Bond
1
2
3
4
Sn1–Cl1
Sn1–S1
Sn1–C6
Sn1–C12
Sn1–N2
C1–S1
2.461(7)
2.431(5)
2.14(2)
2.09(2)
2.35(2)
1.74(3)
2.465(1)
2.418(1)
2.121(3)
2.122(3)
2.399(3)
1.752(3)
Fig. 3. The Mo¨ssbauer spectrum of Sn(acsbz)Ph2Cl.
1.662(5),1.649(5),
1.663(5),1.652(5)
1.346(6),1.337(6),
1.344(6),1.344(6)
1.387(5),1.393(5),
1.395(5),1.384(5)
1.655(4)
Table 4
Mo¨ssbauer spectroscopic data for the diphenyltin(IV) complexes
C1–N1
N1–N2
1.332(4)
1.393(4)
1.393(4)
1.29(3)
1.43(3)
1.272(4)
1.412(3)
Compound
d (mmsÀ1
)
D (mmsÀ1
)
q
Sn(acsme)(C6H5)2Cl
Sn(acsbz)(C6H5)2Cl
1.28
1.28
2.58
2.59
2.02
2.02
Angles (°)
3
4
C(6)–Sn1– C(12)
C(6)–Sn1–N(2)
C(12)–Sn1–N(2)
C(6)–Sn1–S(1)
C(12)–Sn1–S(1)
N(2)–Sn1–S(1)
C(6)–Sn1–Cl(1)
C(12)–Sn1-Cl(1)
N(2)–Sn1–Cl(1)
S(1)–Sn(1)–Cl(1)
129.3(7)
88.2(7)
94.2(9)
115.7(7)
114.4(4)
76.8(5)
94.6(6)
96.4(6)
162.3(5)
86.2(2)
127.1(1)
88.92(11)
94.66(11)
118.29(10)
113.78(11)
76.38(7)
‘A’ is shown in Fig. 4. H-bonding in the structure finds that
molecules A and D forms centrosymmetric H-bonded
dimers while molecules B and C pair up in a pseudocentro-
symmetric arrangement involving N1n-HÁ Á ÁS2n pairs (data
not shown).
94.11(9)
96.02(10)
163.97(7)
88.37(4)
However, the asymmetric unit of Hacsbz contains only
one molecule which too is H-bonded to a centrosymmetri-

982
M.A. Ali et al. / Polyhedron 27 (2008) 977–984
cally related molecule in the same manner as molecules A
and D in the structure of Hacsme. The crystal structures
of the Schiff bases also confirm that both ligands crystallize
in their thione tautomeric forms as previously predicted by
spectroscopic techniques with the thione sulfur atom trans
to the azomethine nitrogen atoms. In this conformation
these ligands are unable to bind the tin atom as bidentate
NS chelating ligands but, in solution, a 180° rotation about
the C1–N1 bond enables them to act as bidentate chelating
˚
agents. The C1–S1 bond lengths (ꢀ1.65 A) indicate that
they are essentially double bonds but the length of the
C3–N2 bond is intermediate of a single and double bond
indicating electron delocalization in the –N–C–S (thioam-
ide) group.
3.3. Crystal structures of the Sn(IV) complexes
Fig. 7. ORTEP3 view of 4 Sn(acsbz)Ph2Cl (30% probability ellipsoids).
The crystal structures of the two Sn complexes are
shown in Figs. 6 and 7 and important bond lengths and
bond angles are given in Table 5.
and Cl(1), C(6), C(12) and N(2) as donors defining the
basal plane.
The structures show that the tin atom in each compound
is five-coordinated with the deprotonated Schiff base che-
lates the metal ion via the azomethine nitrogen atom and
the thiolate sulfur atom. The phenyl and chloro ligands
occupy the remaining three coordination positions of the
coordination polyhedron. The stereochemistry adopted
by the metal is intermediate between a trigonal-bipyramid
(TBPY) and a square-pyramid (SPY). This may be illus-
trated by considering distortion from an ideal TBPY geom-
etry. Thus, taking the azomethine nitrogen atom (N2) and
the chloro ligand as the axial donor atoms, angles of
163.2(6)° and 163.97(7) are subtended in 3 and 4, respec-
tively, which are much smaller than the ideal value of
180°. The coordinate angles between the equatorial donors
(C6, C12 and S1) also show marked differences from their
ideal 120° values. A similar comparison can also be made
for an ideal SPY geometry taking S1 as the apical donor
An angular structural parameter, s (index of trigonal-
ity) has been proposed previously [27] for distinguishing,
quantitatively, between a distorted trigonal-bipyramid
and a distorted square-pyramid in five-coordinate com-
plexes. The parameter s = b À a/60° where a and b are
the two largest angles; s = 0 for an ideal SPY geometry
(a and b = 180°) and s = 1 for an ideal TBPY geometry.
Using this criteria the s values of the present complexes
are found to be 0.6 indicating distortion that is some-
where between both extrema, but tending slightly toward
TBPY. The largest deviations from ideal geometry are
attributable to the restricted bite size of the chelating
Schiff base.
The Sn–S distances in both complexes are close to the
˚
sum of the covalent radii (2.42 A) but much shorter than
˚
the sum of their van der Waal’s radii [4.0 A] indicating
the formation of a genuine Sn–S bond. The Sn–N distances
in 3 and 4 are only slightly larger than the sum of the non-
˚
polar covalent radius (2.15 A) again indicating strong Sn–
N interactions. A comparison of Sn-donor atom distances
in the present diphenyltin(IV) complexes with those of
related tin(IV) complexes is presented in Table 6 where
the influence of coordination number and ligands is
illustrated.
The five-membered chelate ring in 4 adopts an envelope
conformation with the atoms C1 and N1 each lying ca.
˚
0.3 A out of the plane defined by Sn1, N2 and S1, while
the same chelate ring in 3 is essentially planar within exper-
imental uncertainty. A comparison of the bond distances in
the dithiocarbazate chain shows that in both tin complexes
the C–S bonds are longer than observed in the respective
free ligands but intermediate between those characteristic
˚
˚
of single C–S (ꢀ1.85 A) and double bonds (ꢀ1.56 A).
Coordination of the ligands to the tin atom in their imino-
thiolate forms raises the C1–N1 bond order at the expense
of the C1–S1 bonds.
Fig. 6. ORTEP3 view of 3 Sn(acsme)Ph2Cl (30% probability ellipsoids).

M.A. Ali et al. / Polyhedron 27 (2008) 977–984
983
Table 6
Comparison of Sn-donor atom distances in some organotin(IV) complexes
Sn–S
Sn–C
Sn–Cl
Sn–Nazo
Ref.
Sn(actsc)2Ph2Cl2
Sn(acsme)2Cl2
Sn(acsme)Ph2Cl
2.72
2.457(4)
2.431(5)
2.142(3)
2.569(1)
2.4000(5)
2.461(7)
[20]
[29]
2.313(11)
2.35(2)
2.14(2)
2.09(2)
2.121(3)
2.122(3)
2.105(7)
2.108(7)
This work
This work
[28]
Sn(acsbz)Ph2Cl
2.418(1)
2.478(2)
2.465(1)
2.672(1)
2.399(3)
2.359(4)
[Sn(CH3)2(Pytsc)Cl]Á0.5H2O
[3] M. Akbar Ali, A.H. Mirza, T.B.S.A. Ravoof, P.V. Bernhardt,
Polyhedron 23 (2004) 2031.
3.4. Conclusions
[4] M. Akbar Ali, Aminul Huq Mirza, Ray J. Butcher, Karen A. Crouse,
Trans. Met. Chem. 31 (2006) 9.
[5] M. Akbar Ali, A.H. Mirza, C.W. Voo, A.L. Tan, P.V. Bernhardt,
Polyhedron 22 (2003) 3433.
[6] M. Akbar Ali, A.H. Mirza, M. Nazimuddin, R. Ahmed, L.R. Gahan,
P.V. Bernhardt, Polyhedron 22 (2003) 1471.
[7] M. Akbar Ali, A.H. Mirza, See Tho Wai Keng, R.J. Butcher, Trans.
Met. Chem. 28 (2003) 241.
In the solid state, the acetone Schiff bases of S-methyl
and S-benzyldithiocarbazate, like all other Schiff bases
derived from S-alkyl esters of dithiocarbazic acid, remain
in their thione tautomeric forms with the thione sulfur
atom trans to the azomethine nitrogen atom but in solution
they convert to the thiol form accompanied by an inversion
of N2 with the concomitant formation of diphenyl-
tin(IV)chloride complexes of the deprotonated Schiff bases.
Spectroscopic and X-ray diffraction studies show that the
substituents on one of the sulfur atoms of the dithiocarbaz-
ate moiety virtually have no effect on the s-electron density
at the tin nucleus and on the stereochemistry adopted by
the tin complexes.
[8] (a) M. Akbar Ali, A.H. Mirza, M. Nazimuddin, H. Rahman, R.J.
Butcher, Trans. Met. Chem. 27 (2002) 268;
(b) M. Akbar Ali, A.H. Mirza, M. Nazimuddin, P.K. Dhar, R.J.
Butcher, Trans. Met. Chem. 27 (2002) 27;
(c) M. Akbar Ali, A.H. Mirza, R.J. Butcher, M.T.H. Tarafder, Manaf
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[11] (a) G. Davies, M.A. El-Sayed, A. El-Toukhy, Inorg. Chem. 25 (1986)
2269, and references therein;
4. Supplementary material
(b) S. Al-Sheri, G. Davies, M.A. El-sayed, A. El-Toukhy, Inorg.
Chem. 29 (1990) 1198.
CCDC 653521, 653522, 653523 and 653524 contain the
supplementary crystallographic data for 1, 2, 3 and 4.
These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or
e-mail: deposit@ccdc.cam.ac.uk.
[12] K.A. Crouse, Kar-Beng Chew, M.T.H. Tarafder, A. Kasbollah, A.M.
Ali, B.M. Yamin, H.-K. Fun, Polyhedron 23 (2004) 161.
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[15] (a) M.T.H. Tarafder, Kar-Beng Chew, K.A. Crouse, A.M. Ali, B.M.
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(c) M.E. Hossain, M.N. Alam, J. Begum, M. Akbar Ali, M.
Nazimuddin, F.E. Smith, R.C. Hynes, Inorg. Chim. Acta 249
(1996) 207.
Acknowledgements
M.A.A., A.H.M. and M.H.S.A.H. thank Universiti of
Brunei Darussalam for financial support. Thanks are also
due to Dk. Misliha Nurhayati Bte Pg. Hj Samsudin and
Naziah Bte Sahat for their technical help. O.A., X.S.,
G.E. and L.M. acknowledge with thanks the financial sup-
port for the 119Sn Mo¨ssbauer work from the National
Institute of Health, Biomedical Research Support Program
(MBRS/SCORE, GM08005). P.V.B. acknowledges
support from the Australian Research Council and the
University of Queensland.
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Germany, 1986.
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