Coordination Chemistry of Iridium Phosphine–Sulfonate Complexes

Abstract

A family of new iridium phosphine–sulfonate complexes based on 2-dicyclohexylphosphino-4-benzenesulfonic acid was synthesized and characterized. An iridium(I) phosphine–sulfonate cyclooctadiene species was prepared from transmetalation of a silver salt of the phosphine–sulfonate ligand and iridium(I) cyclooctadiene chloride dimer. This diolefin iridium complex was found to be a functional precatalyst for cyclopentene hydrogenation. A corresponding iridium(I) phosphine–sulfonate dicarbonyl species was prepared by ligand substitution using carbon monoxide. Analysis by infrared spectroscopy established this metal–ligand platform as a relatively electron poor coordination environment. The iridium(I) phosphine–sulfonate cyclooctadiene species was further utilized as a precursor for the synthesis of two iridium(III) phosphine–sulfonate hydride compounds by treatment with strong acids.