PLATINUM AND RHODIUM COMPLEXES OF DIALKENYL TELLUROETHER LIGANDS - SYNTHESIS, DYNAMIC NUCLEAR-MAGNETIC-RESONANCE AND CRYSTAL-STRUCTURE OF YL-5-TELLURA-3,7-DISILANONA-1,8-DIENE)PLATINUM(II)

A number of dialkenyl telluroether ligands have been synthesised. Reac tion with platinum(II) and rhodium(I) metal centres at low temperature in non-aqueous media yielded complexes in which the ligands are biden tate (binding through the tellurium atom and one alkene function) and tridentate. respectively. The bidentate platinum complexes are fluxion al, exhibiting exchange of the alkene moieties. the energy barriers fo r which have been evaluated. Tellurium-125 NMR data have been obtained and are discussed with reference to the chelate ring effect. The crys tal structure of [PtBr2{Te(CH(2)SiMe(2)- CH=CH2)(2)}] has been determi ned: crystals are triclinic of space group P (1) over bar with a = 6.5 837(9), 6 = 8.8594(8), c = 17.860(2) Angstrom, a = 98.65(2). beta = 97 .73(1), gamma = 111.26(1)degrees and Z = 2. The structure is monomeric with the platinum atom exhibiting square-planar geometry. The two bro mine atoms are mutually cis and the di(silaalkenyl) telluroether ligan d chelates to the metal via the tellurium atom and one alkene moiety.