Zia-ur-Rehman et al. / Inorganica Chimica Acta 361 (2008) 3322–3326
3323
the hydrogen atoms were generated by geometrical consider-
ations; methyl-groups were defined as rigid groups which were al-
lowed to rotate free. Final refinement on F2 carried out by full-
matrix least-squares techniques using SHELXL-97. Some atoms in
the solution for 2 showed unrealistic parameters when refined
anisotropically due to the weak scattering power of the crystals
examined. To improve the parameters, restraints were applied in
the refinement of the structure of 2.
Fig. 1. Numbering scheme for 4-(2-methoxyphenyl)piperazine-1-carbodithioic
acid (MPPDAH).
ð1Þ
2.2. Synthesis
2.2.1. 4-(2-Methoxyphenyl)piperazine-1-carbodithioic acid (MPPDAH)
Dropwise addition of CS2 (3.0 mmol) in methanol (50 mL) to
1-(2-methoxyphenyl)piperazine (5.0 g, 3.0 mmol) in methanol
(50 mL) followed by stirring for 4 h at room-temperature gave
the white product. This was filtered and washed with diethyl ether
(Yield: 5.9 g, 85%). M.p. 161–163 °C. Anal. Calc. for C12H15N2OS2: C,
53.70; H, 6.01; N, 10.44; S, 23.89. Found: C, 53.60; H, 6.23; N,
10.56; S, 23.77%. Raman (cmꢀ1): 569 m(C–S), 1215 m(C@S), 2447
ð2Þ
3. Results and discussion
m(SH). 1H NMR (ppm): 3.6 (m, H2;2 ), 4.6 (m, H3;3 ), 3.9 (s, H10), 8.5
(s, SH) 7.1–6.9 (m, C6H5). 13C NMR (ppm): 209.6 (C-1), 48.4
(C-2,20), 50.8 (C-3,30), 55.5 (C-10), 111.4 (C-5), 118.4 (C-8), 121.1
(C-7), 123.8 (C-6), 140.6 (C-4), 152.3 (C-9).
0
0
3.1. Synthesis
The ligand was obtained from the reaction of 1-(2-methoxy-
phenyl)piperazine with carbon disulfide in dry methanol (Eq.
(1)). The organotin(IV) derivatives, 1 and 2, were then synthesized
by the reaction of MPPDAH with R2SnCl2 (R@Me or Et) as shown in
Eq. (2). Both products are white crystalline solids, soluble in a
range of organic solvents, e.g. benzene, chloroform, as well as
THF, acetone, and DMSO. They are less soluble in methanol or eth-
anol and effectively insoluble in water.
2.2.2. Me2SnCl(MPPDA) (1)
Me2SnCl2 (0.40 g, 1.86 mmol) in methanol (30 mL) was added
dropwise to MPPDAH (0.50 g, 1.86 mmol) in methanol (30 mL)
and the mixture was refluxed for 3 h with stirring. The white prod-
uct was filtered and recrystallized from chloroform–ethanol to give
colourless crystals (Yield: 0.65 g, 66%). M.p. 136–138 °C. Anal. Calc.
for C14H21N2OS2SnCl: C, 37.23; H, 4.69; N, 6.20; S, 14.20. Found: C,
36.90; H, 4.67; N, 6.10; S, 13.90%. Raman (cmꢀ1): 286 m(Sn–Cl), 396
m(Sn–S), 499 m(Sn–C), 527 m(C–S), 1188 m(C@S). 1H NMR (ppm): 3.2
3.2. Raman spectra
0
0
The Raman peak corresponding to the NH stretch of 1-(2-
methoxyphenyl)piperazine disappears upon reaction with CS2
and the formation of MPPDAH is also indicated by appearance of
features assigned to m(SH), m(C–S) and m(C@S) modes. After the
reaction of MPPDAH with R2SnCl2, the peak associated with the
m(SH) disappears and the vibrational mode corresponding to tin–
sulfur appears at ꢁ397 cmꢀ1. In addition, Raman spectra of com-
plex 1 and 2 display peaks associated with the chlorodiorganotin
moiety, m(Sn–C) and m(Sn–Cl).
(m, H2;2 ), 4.2 (m, H3;3 ), 3.9 (s, H10), 7.1–6.9 (m, C6H4), 1.4 (s,
SnCH3), 78 Hz [2J(119Sn, 1H)]. 13C NMR (ppm): 196.1 (C-1), 49.8
(C-2,20), 51.9 (C-3,30), 55.9 (C-10), 111.4 (C-5), 118.6 (C-8), 121.1
(C-7), 124.2 (C-6), 139.4 (C-4), 152.2 (C-9), 12.8 (SnCH3). 119Sn
NMR: d ꢀ192.9 ppm.
2.2.3. Et2SnCl(MPPDA) (2)
Compound 2 was prepared in the same way as 1, using the same
molar amounts, to give colourless crystals (Yield: 0.71 g, 79%). M.p.
184–186 °C. Anal. Calc. for C16H25N2OS2SnCl: C, 40.06; H, 5.25; N,
5.84; S, 13.37. Found: C, 39.81; H, 5.33; N, 5.81; S, 13.15%. Raman
(cmꢀ1): 267 m(Sn–Cl), 398 m(Sn–S), 468 m(Sn–C), 563 m(C–S), 1183
m(C@S). 1H NMR (ppm), {nJ(1H, 1H), Hz}, [nJ(119Sn, 1H), Hz]: 3.2
(m, H2;2 ), 4.3 (m, H3;3 ), 3.9 (s, H10), 7.1–6.9 (m, C6H4), 2.1 (q, Sn–
CH2CH3) {7.8} [71], 1.5 (Sn–CH2CH3). 13C NMR (ppm), [nJ(119Sn,
13C), Hz]: 200.4 (C-1), 50.2 (C-2,20), 51.3 (C-3,30), 55.5 (C-10),
111.3 (C-5), 118.5 (C-8), 121.1 (C-7), 123.8 (C-6), 140 (C-4), 152.2
(C-9), 10.9 (SnCH3) [49], 27.9 (Sn–CH2), [608]. 119Sn NMR: d
ꢀ187 ppm.
3.3. NMR spectra
Comparing the 1H NMR spectra of complexes 1 and 2 with that
of MPPDAH showed the disappearance of the signal for the SH pro-
ton owing to complexation with the alkyltin moiety. The 2J(119Sn,
1H) values for complexes 1 and 2 were 78.0 and 71.4 Hz, respec-
tively, in the range normally expected for 5-coordinate tin [16]
and consistent with CSnC angles of 128° and 118°. The 13C chemi-
cal shifts observed for the two complexes were similar to those for
the parent MPPDAH. Only a small shift in the position of C(1) was
noted which resulted from deshielding of this particular carbon
atom upon deprotonation of the thiol group and coordination
through both sulfur atoms. The alkyl groups attached to the tin
atoms showed signals in the expected range. Moreover, the
1J[119Sn,13C] coupling constant observed for complex 2, 608 Hz,
was the same as that reported for analogous 5-coordinate deriva-
tives [17,18]. The 119Sn NMR spectra of 1 and 2 displayed sharp sig-
nals at ꢀ192.9 and ꢀ187 ppm, respectively, which were consistent
with those for similar five-coordinate organotin(IV) dithiocarba-
mates [19,20].
0
0
2.3. X-ray crystallography
For both crystals, X-ray data were collected on a Bruker SMART
APEX CCD diffractometer using graphite-monochromated Mo Ka
radiation (k = 0.71073 Å). Data collection used /- and x-scans,
and a multi-scan absorption correction was applied in both cases.
The structure of complex 1 was solved by Patterson synthesis fol-
lowed by direct methods applied to difference structure factors
using the program DIRDIF. The structure of compound 2 was
solved by direct methods using the program SIR2004. In both cases,