Substitution and isomerisation reactions at platinum(II) involving halide, tertiary phosphine, carbonyl, and lsonitrile ligands
Abstract
Carbon monoxide catalyses trans to cis isomerisations of [PtCl2L2](L = tertiary phosphine) in chloroform solution. The process involves formation of five-co-ordinate intermediates from which halide or tertiary phosphine can be eliminated, giving trans-[PtCl(CO)L2]+ or cis-[ PtCl2(CO)L] respectively. Structure changes appear to be by pseudo-rotations rather than by consecutive displacements. A number of isonitrile complexes undergo similar reactions. Halide-bridged cations [Pt2(µ-Cl)2L4]2+ formed by halide extraction from cis-[PtCl2L2] by Ag+ enter rapid (n.m.r. time-scale) exchange processes with the latter complexes at ambient temperatures. Halide elimination from cis-[PtCl2L2] by solvent chloroform appears to initiate the process. The trans isomers do not participate in the exchange.