SYNTHESIS AND SPECTROSCOPIC STUDIES OF PALLADIUM AND PLATINUM COMPLEXES OF METHYLENE-BACKBONED DITHIO-ETHER, DISELENO-ETHER AND DITELLURO-ETHER LIGANDS, RECH2ER (R=ME OR PH - E=S, SE OR TE)

The complexes [ML2Cl2] (M = Pd or Pt; L = PhSCH2SPh, MeSCHSMe, PhSeCH2SePh or MeSeCH2SeMe), which are square planar with monodentate sulfur or selenium ligands, have been prepared. In the solid state, on the basis of IR and Raman data, the palladium complexes are trans and the platinum cis, whilst in solution multinuclear NMR spectroscopy (H-1, Pt-195-{H-1}, and Se-77-{H-1}) reveal that both cis and trans isomers and meso and DL enantiomers are present, the isomer populations varying with L and M in a systematic way. The complexes [MLCl2] are stable in solution for L = PhSCH2SPh, but the other complexes lose L to precipitate polymeric [(MLCl2)n] complexes. The ditelluroethers, MeTeCH2TeMe and PhTeCH2TePh, form only the latter type of complex. The crystal structure of trans-[Pd(PhSCH2SPh)2Cl2] has been determined and contains a trans square-planar palladium atom with one co-ordinated and one free sulfur atom associated with each dithioether ligand [Pd-Cl 2.292(l) and Pd-S 2.329(l) angstrom].