Synthesis and molecular structures of platinum and mercury complexes chelated by (phenylthiomethyl)silane ligands

Metathesis reaction of the dithioether complex cis-[PtCl2 {(PhSCH2)(2)SiPh2}] (2a) with NaBr and NaI yields the square planar complexes cis-[PtX2{(PhSCH2)(2)SiPh2}] (2b, X = Br; 2c, X = 1). The new compounds, which are fluxional in solution, have been studied by multinuclear NMR techniques; the crystal structures of 2a-c have been determined by X ray diffraction. This series allows to evaluate the trans-influence of the halide ligands on the lengths of the Pt-S bonds, which increase from 227.26(12) (2a), 228.46(13) (2b) to 229.96(15) (2c) pm due to a more pronounced trans-influence of I compared with Br and Cl. Complexation of (PhSCH2)(2)SiPh2 (1a) on HgBr2 gives the distorted tetrahedral compound [HgBr2{(PhSCH2)(2)SiPh2}] (3), having a quite loose coordination of the ligand both in solution and in the solid state [Hg-S = 291.88(2) pm]. Alternatively, the coordination around Hg may be described as distorted square pyramidal in the solid state, since to due to a weak intermolecular Hg...Br interaction [346.72(13) pm], a dimeric motif is formed. Furthermore, the functionalised cyclic silane (PhSCH2)(2)SiC4H6 (1b) has been prepared and co-ordinated as chelating dithioether ligands to [PtCl2(PhCN)(2)] affording the dithioether complex cis-[PtCl2{(PhSCH2)(2)SiC(4)H6)}] (4). The crystal structure of 4 has also been determined by an X-ray diffraction study.