Reactions of dimethyl- and diphenyl-platinum(II) complexes and isocyanides

Abstract

Reactions of PtR 2L 2 species (R = CH 3, C 6H 5; L = several phosphines) with methyl and p-chlorophenyl isocyanides were found to proceed either with ligand substitution or isocyanide insertion into the carbonmetal bond; the type of reaction was dependent on the nature of the phosphine and isocyanide. Substitution yielding PtR 2(CNR′)(Phos), occurred for Phos = PPh 3 with both isocyanides and for PPh 2-Me, with p-chlorophenyl isocyanide; insertion occurred for Phos = PEt 3 for both isocyanides and for PPhMe 2 with p-chlorophenyl isocyanides. Interestingly, no product was isolated in the reactions of PtR 2Phos 2 (Phos = PPh 2Me and PPhMe 2) with methyl isocyanide, a result attributed to the unfavorable position of an equiliborium, PtR 2Phos 2 + CNMe ⇌ PtR 2(CNMe)Phos + Phos, in these systems. If methyl iodide is added to these reaction systems two possible reactions can occur. A deficiency of methyl iodide can quaternize the free phosphine allowing the isocyanide substitution reaction product to be isolated (Phos = PPh 2Me only). Alternatively, excess methyl iodide will add oxidatively to give the platinum(IV) species PtIMe 3(L)Phos (L = Phos or CNMe).