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.