PACKING EFFECTS DUE TO SOLVATE MOLECULES.
THE STRUCTURE OF TRANS-DICHLOROBISTRIPHENYLARSINEPLATINUM(II).

Maria Johansson1, Åke Oskarsson1, Fanie Otto2 and André Roodt2.

1. Inorganic Chemistry 1, Chemical Center, University of Lund, P.O. Box 124, S-221 00 Lund, Sweden
2. University of the Free State, P.O. Box 339, Bloemfontein, 9300, South Africa

Keywords: Platinum, Arsenic, Probability plots

Four different crystallization products of trans-dichlorobistriphenylarsine-platinum(ii) has been structurally characterized by X-ray crystallography and their geometric differences caused by packing and solvent molecules are analysed by half-normal probability plots and R.M.S. deviations.

The Pt-compound was prepared by adding AsPh3 to an acetone solution of [PtCl2(SMe2)2]. The product precipitates spontaneously and was recrystallized from four different solvents.

When recrystallized from 1,1,1-trichloroethane, it crystallises without solvent (1) in the monoclinic space group P21/a with Z=2 and with cell dimensions a=9.271(2), b=19.726(4), c=9.830(2) Å, b=111.83(3)° and V= 1668.8(6) Å3.

By desolving the complex in dichloromethane the compound crystallizes with one solvent molecule (2) in the orthorhombic space group Pbca with Z=4 and a=20.582(4), b=8.146(2), c=23.491(5) Å and V=3938.5(14) Å3.

With dichloroethane the compound also crystallizes with one solvent molecule (3) but in the triclinic space group P1- with Z=1 and a=9.384(2), b=9.549(2), c=11.919(2) Å, a=109.70(3), b=108.34(3), g=98.88(3)° and V=913.0(3) Å3.

When recrystallized from benzene the compound crystallizes with half a solvent molecule (4) in the monoclinic space group P21/n with Z=4 and a=11.785(2), b= 18.721(4), c=16.663(3) Å, b=104.74(3)° and V=3555.2(12) Å3.

The total number of reflections collected with a Smart CCD system are 5096, 7901, 5381 and 10893 (q <= 31.7) for (1) to (4) using MoKa radiation and the final R-values are 0.0251, 0.0311, 0.0380 and 0.0296, respectively.

In all four compounds platinum(II) binds to triphenylarsin and chloride in a pseudo square-planar trans configuration. The Pt-As distances are 2.4104(4) and the Pt-Cl distances are 2.3004(11) Å in (1). The Pt-As and Pt-Cl distances in (2), (3) and (4) are similar to those in (1). The solvent has a large influence on the packing, resulting in different space groups or different occupancies in the same space group (1 and 4). The largest differences in the four complexes are observed in the bond- and torsion-angles involving the chloride atom.