Oxidative addition of diphenylphosphinoacetic acid to rhodium: crystal structures of the intermediate, [RhCl(H)(Ph2PCH2CO2-OP)(Ph2PCH2CO2H-P)2] and of the final product, [Rh(Ph2PCH2CO2-OP)3]

Abstract

The difference in reactivity towards Rh^I between simple tertiary phosphines and diphenylphosphino-acetic acid can be explained by the assumption that the latter ligand, besides monodentate P bonding, tends also to react by oxidative addition of its carboxyl group, yielding P,O-chelated rhodium(III) complexes. Crystal structures of the final product, fac-[Rh(Ph₂PCH₂CO₂)₃]·PhNO₂·H₂O, and of the key intermediate, mer-[RhCl(H)(Ph₂PCH₂CO₂)(Ph₂PCH₂CO₂H)₂]·C₄H₈O, were determined. The latter structure is unique in that it contains both hydride and a carboxylic proton in one molecule.