metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
Pd—S bond lengths (Table 1) are sligthly shorter and longer,
respectively, than those observed in Pd complexes containing
bis-N,S-chelating dithiocarbazate ligands, which fall in the
˚
ISSN 0108-2701
ranges 2.067–2.111 and 2.253–2.268 A, respectively, as
retrieved from the Cambridge Structural Database (CSD,
Version 5.31 of November 2009; Allen, 2002). Inside the C—
N—N—C group, the bond distances follow the trend found in
the other Pd complexes retrieved, indicating that C9—N1 and
N2—C1 are double bonds and N1—N2 is a single bond. As
described in the Experimental section, the octyloxy chain is
disordered over two positions, leading to absolute O1—C17—
C18—C19 torsion angles of 66.6 (14) and 162.7 (17)ꢀ for the
two arrangements, corresponding to synclinal and anti-
periplanar conformations, respectively. The former is close to
that found in the octyloxybenzaldehyde thiosemicarbazone
ligand (Islam et al., 2010).
Bis[S-benzyl-3-(4-n-octyloxybenzyl-
idene)dithiocarbazato-j2N3,S0]-
palladium(II)
M. T. H. Tarafder,a M. A. A. A. A. Islam,b M. B. H.
Howlader,a N. Guidolinc and E. Zangrandoc*
aDepartment of Chemistry, Rajshahi University, Rajshahi 6205, Bangladesh,
bDepartment of Chemistry, Rajshahi University of Engineering and Technology,
c
`
Rajshahi 6204, Bangladesh, and Dipartimento di Scienze Chimiche, Universita di
A key interest in bis-N,S-bidentate complexes of Ni triad
metals is the adoption of cis versus trans geometries. A CSD
search for the fragment M[SC(S)NN]2 (where M = Ni, Pd or
Pt) indicates that Ni complexes with N,S-chelating dithio-
carbazate groups adopt either a cis (12 entries) or a trans
geometry (12 entries) with equal probability. By contrast, five
out of six Pd complexes have a cis configuration, while all five
Pt complexes adopt a trans arrangement. The unique reported
Pd complex with a trans geometry is notable in that the
S-benzyldithiocarbazate ligand has an NH2 group (Tampouris
et al. 2007) as the coordinating N atom, rather than an alkyl- or
alkylidene-substituted N atom.
Trieste, Via Licio Giorgieri 1, 34127 Trieste, Italy
Correspondence e-mail: ezangrando@units.it
Received 16 July 2010
Accepted 27 October 2010
Online 6 November 2010
In the title compound, [Pd(C23H29N2OS2)2], the PdII atom
displays the expected square-planar coordination geometry.
However, the trans configuration, which allows the PdII atom
to be located on a crystallographic inversion centre, is unusual
with respect to the cis arrangement found in analogous Pd
complexes comprising similar N,S-chelating ligands.
Comment
Metal chelates of S-alkyl/aryl esters of dithiocarbazate
(SBDTC) and their Schiff bases have attracted the interest of
researchers for their coordination chemistry and also for their
potential use as anticancer compounds (Maurya et al., 2003;
How et al. 2008; Crouse et al., 2004; Tarafder et al., 2001, 2002;
Ali et al., 1992). As a continuation of our interest in N,S-donor
ligands and their complexes, we have isolated a novel Schiff
base of SBDTC, S-benzyl-3-[(4-n-octyloxyphenyl)methylene]-
dithiocarbazate, and its bis-bidentate palladium(II) complex,
the title compound, (I).
Although the Pd and Pt dithiocarbazate complexes are
fewer in number, there is a fair indication that these metals
prefer a cis (Pd) or a trans (Pt) geometry, although it should be
noted that a broader search of Pd complexes of bis-bidentate
ligands with N—C—C—S (nine cis versus five trans) or N—
N—C—S (10 cis versus 17 trans) linkages shows no clear
preference. Thus, we can say that (I) represents a rare example
of a bis(dithiocarbazato)palladium(II) ion in a trans-planar
coordination geometry (see scheme above), likely assumed in
order to avoid steric clashes between the substituents on the
ligand. The (ferrocenyl)ethylidene (Duan et al., 1998) and
diazafluorene–dithiocarbazate (Zhou et al., 2007) derivatives,
which have bulky groups on the ligand and a cis configuration,
appear to be stabilized by intramolecular stacking interactions
between the cyclopentadienyl planes from different Fe atoms
and between the diazafluorene rings, respectively. Since no
stacking interaction between phenyl rings is detected in (I),
intermolecular packing forces favouring the trans geometry
appear to be excluded. In the absence of such effects, the
stabilization of one configuration over the other may result
from the different trans influence exerted by the N and S
The structure of (I) shows the PdII ion in the expected
square-planar donor environment (Fig. 1), with the metal
atom on a centre of inversion and the asymmetric unit
therefore constituted by half of the molecule. Each of the
ligands is coordinated to the metal as a bidentate chelating
agent bonding via the thiolate S and azomethine N atoms,
yielding two five-membered chelate rings. The Pd—N and
Acta Cryst. (2010). C66, m363–m365
doi:10.1107/S0108270110044008
# 2010 International Union of Crystallography m363
Tarafder
