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 mo de 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 whi ch have been evaluated for the platinum systems. The crystal structure s 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 crystal s 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 = 105.2 6(2)degrees and Z = 1. The platinum complex is monomeric and has a squ are-planar geometry with the iodine atoms in cis positions, whilst the rhodium complex is a centrosymmetric dimer with two chlorine atoms br idging a pair of rhodium atoms, both having trigonal-bipyramidal geome try.