Platinum metal complexes of potentially chelating alkene–thioether and alkene–selenoether ligands: synthesis and dynamic nuclear magnetic resonance study of [MX2{MeE(CH2)nCHCH2}](M = Pt or Pd; X = Cl, Br, or I; E = S or Se; n= 2 or 3) and the X-ray structure of cis-dibromo(2-thia-6-heptene)platinum(II), [PtBr2{{MeS(CH2)3CHCH2}]

Abstract

But-3-enyl and pent-4-enyl methyl chalcogenide ligands have been found to co-ordinate to transition metals through the chalcogen atom alone in a monodentate fashion, or as bidentate ligands binding through both the chalcogen atom and the alkene moieties. The metallacycles formed on chelation have been fully characterised and an X-ray diffraction study of [PtBr₂{MeS(CH₂)₃CHCH₂}] is reported: the crystals are orthorhombic, of space group Pbca with Z= 8 in a unit cell of dimensions a= 15.098(9), b= 13.245(3), and c= 10.299(2)Å The principal internuclear distances are Pt–Br 2.448(4) and 2.434(4), Pt–S 2.286(7), and Pt–C 2.136(20) and 2.196(19)Å. Inversion of configuration at the co-ordinated sulphur atom is observed at moderate temperatures and has been studied by dynamic n.m.r. spectroscopy. The methyl pent-4-enyl sulphide ligand is observed to isomerise upon co-ordination to palladium(II).