SYNTHETIC, DYNAMIC NUCLEAR-MAGNETIC-RESONANCE AND CRYSTALLOGRAPHIC STUDIES OF PLATINUM COMPLEXES CONTAINING SILYL-SUBSTITUTED DIALKENYL-THIOETHER AND DIALKENYL-SELENOETHER LIGANDS

Potentially quadridentate di(silaalkenyl) chalcogenoether ligands have been observed to bind in a bidentate mode via an alkene moiety and a chacogen lone pair of electrons to platinum(II) and in a tridentate mode to rhodium(I) metal centres, via the chalcogen atom and both alkene moieties. Variable-temperature NMR studies established the occurrence of fluxional processes in these complexes, the energy barriers of which have been evaluated for the platinum systems. The crystal structures of two species have been determined: [Ptl(2){S(CH(2)SiMe(2)CH=CH2)(2)}] forms monoclinic crystals of space group P2(1)/a with a = 12.279(5), b = 8.961(3), c = 18.575(3) Angstrom, beta = 108.49(2)degrees and Z = 4 and [{RhCl[S(CH(2)SiMe(2)CH=CH2)(2)]}(2)] forms triclinic crystals of space group P (1) over bar with a = 7.7178(12), b = 10.289(4), c = 10.5932(14) Angstrom, a = 92.56(2), beta = 99.544(14), gamma = 105.26(2)degrees and Z = 1. The platinum complex is monomeric and has a square-planar geometry with the iodine atoms in cis positions, whilst the rhodium complex is a centrosymmetric dimer with two chlorine atoms bridging a pair of rhodium atoms, both having trigonal-bipyramidal geometry.