metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
present context, we wanted to examine the question from a
structural perspective. The chosen vehicle for the study was
the array of bis(monodentate nitrile) complexes of stannic
chloride. Only the structure of the acetonitrile complex has
been recorded previously (Webster & Blayden, 1969), showing
the metal-atom stereochemistry to be quasi-octahedral six-
coordinate, with the nitrile ligands in cis positions in the
coordination sphere, cis-[SnCl4(MeCN)2], in a situation where
the ꢀ-donor character of the ligand might be expected to
predominate. [Two determinations of the one-dimensional
polymer stannic chloride±glutaronitrile (1/1) are recorded
(Barnhart et al., 1968; Liu, 1985), also with two nitrile donors
from different ligands in cis positions in the coordination
sphere.]
Attempts were made to crystallize a number of such
complexes from solutions of stannic chloride in various nitriles
under Schlenk conditions, by volume reduction and/or by
cooling as necessary. Well formed colourless crystals were
obtained for a diverse array of substituents, R [R is methyl,
ethyl, isopropyl, cyclohexyl (cy) and o-tolyl (o-tol)], and were
subjected to structural study.
ISSN 0108-2701
cis-Bis(acetonitrile)tetrachlorotin(IV)
acetonitrile solvate, cis-tetrachloro-
bis(propiononitrile)tin(IV) propiono-
nitrile solvate, cis-tetrachlorobis(iso-
butyronitrile)tin(IV), cis-tetrachloro-
bis(cyclohexanecarbonitrile)tin(IV)
and cis-tetrachlorobis(o-toluonitrile)-
tin(IV), all determined at ca 150 K
George A. Koutsantonis, Travis S. Morien, Brian W.
Skelton* and Allan H. White
Department of Chemistry, University of Western Australia, Crawley, WA 6009,
Australia
Stannic chloride crystallizes from acetonitrile solution as
SnCl4Á3MeCN. In the belief that one of the acetonitrile groups
was uncoordinated in the original determination, SnCl4Á-
2MeCN was obtained by pumping on the solid in vacuo and
recrystallizing the material from carbon tetrachloride, the
results of the determination establishing the stereochemistry
(Webster & Blayden, 1969). In the present study, it was
considered worth establishing the nature of the 3MeCN
adduct, which was found to be the monosolvate of the cis-bis
complex, cis-[SnCl4(MeCN)2]ÁMeCN, (I). The asymmetric unit
of the structure contains one-half of the formula unit. The
complex molecule is disposed about the crystallographic
mirror plane in space group Pnma, and the Sn atom and the
pair of mutually trans Cl atoms lie in the plane. The substrate
molecule is well de®ned (Fig. 1a), but not so much as to permit
re®nement of the H-atom parameters at the periphery of the
ligand, where the displacement parameters are higher. The
MeCN molecule of crystallization is more problematic; it is
seemingly disordered over a continuous undulating sequence
of residues passing through the cell in the b direction and is
modelled with the terminal C atom in the mirror plane, with
full site occupancy, and the CN group disposed to either side,
with an occupancy of 0.5 (Fig. 1b).
Correspondence e-mail: bws@crystal.uwa.edu.au
Received 30 May 2003
Accepted 9 June 2003
Online 16 August 2003
The structures of the title compounds, [SnCl4(C2H3N)2]Á-
C2H3N, [SnCl4(C3H5N)2]ÁC3H5N, [SnCl4(C4H7N)2], [SnCl4-
(C7H11N)2] and [SnCl4(C8H7N)2], were determined with the
intention of examining the effect of various substituent types
in nitrile ligands, RCN, behaving in a common ꢀ-donor
situation {in this case, as cis-bis complexes with SnCl4, viz.
[SnCl4(RCN)2]}, on (i) the strength of complex formation with
the metal atom and (ii) other bonding behaviour of the metal
(for example, trans effects). The ®ve structures exhibit no non-
trivial systematic perturbation that can be said to be
contingent on the substituent type.
Comment
Organic nitrile ligands in their coordination complexes with
metal atoms are commonly regarded as both ꢀ-donors and
ꢁ-donors, which, having a triple bond (RC N), should be
particularly appropriate for the transmission of electronic
effects of the R substituent through the bonding scheme
linking it to the metal. Presumably, any such effect will be
superimposed on the common observation of the lengthening
of the C N bond on coordination. The substituent is well
removed from the metal and should not interact sterically with
the rest of the coordination environment, unless the substi-
tuent is unusually bulky. However, the rod-like nature of the
ligand may render it susceptible to substantial consequences
of packing forces, which are usually manifested in deviations
from linearity of the MNC linkage, NCR being less suscep-
tible. Such effects can be explored spectroscopically, but in the
The propiononitrile adduct, similarly a cis-bis(ligand)
complex, is also a monosolvate, viz. cis-[SnCl4(EtCN)2]ÁEtCN,
Acta Cryst. (2003). C59, m361±m365
DOI: 10.1107/S0108270103012642
# 2003 International Union of Crystallography m361
Koutsantonis, George A.
