Pyrolysis of diaryl(phosphine)platinum(II) complexes: reductive elimination followed by subsequent decomposition of the platinum-containing residue

Abstract

The condensed-phase thermolyses of complexes [PtR₂L₂] and [PtR₂(P–P)][R = Ph or C₆H₄Me-4; L = PPh₃ or P(C₆H₄Me-4)₃; P–P = Ph₂PC₂H₄PPh₂(dppe) or Ph₂PCH₂PPh₂(dppm)] have been examined by t.g.a., d.t.a., d.s.c., and product analysis. The primary decomposition step is concerted reductive elimination forming R₂. Experiments on mixtures established both that this elimination is intramolecular, and that no scrambling of ligands occurs priorto pyrolysis. Secondary decompositions of [PtL₂] and [Pt(P–P)] give reproducible but non-stoicheiometric amounts of biaryl and arene, probably via insertion of Pt⁰ into aryl–phosphorus and –hydrogen bonds followed by eliminations from Pt. Red-brown glassy residues remain. The mechanisms of these steps and the nature of the residues are discussed.