Cis / trans isomers of Pt X 2 L 2 ( X = halogen, L = neutral ligand); the crystal structure of trans -dichlorobis(dimethyl sulfide)platinum(II) and the pressure dependence of its unit-cell dimensions

trans -PtCl 2 (dms) 2 (dms is dimethyl sulfide) crystallizes in the space group P 2 1 / n and adopts the molecular point group C i , which is the most frequently occurring point group for trans -Pt X 2 L 2 complexes (78%), as observed in the Cambridge Structural Database (CSD; 2005 release), followed by C 1 (16%). Density functional theory calculations show that the observed geometry for trans -PtCl 2 (dms) 2 has slightly higher energy than the most favorable geometry in the point group C 2 h , but this geometry would require a space group that hampers close packing, thus showing that intermolecular forces determine the point group for the title compound. High-pressure powder diffraction studies of trans -PtCl 2 (dms) 2 show no phase transformation up to 8.0 GPa. The bulk modulus is 8.1 (6) GPa and the pressure derivative 8.1 (4). In the CSD, the number of cis - and trans -Pt X 2 L 2 compounds are almost equal, viz. 156 cis and 160 trans compounds, showing no preference for either isomer in the solid state.