π-accepting-pincer rhodium complexes: An unusual coordination mode of PCP-type systems

Abstract

The novel π-accepting, pincer-type ligand, dipyrrolylphoshinoxylene (DPyPX), is introduced. This ligand has the strongest π-accepting phosphines used so far in the PCP family of ligands and this results in some unusual coordination chemistry. The rhodium(I) complex, [(DPyPX)Rh(CO)(PR3)] (4, R=Ph, Et, pyrrolyl) is prepared by treating the relevant [(DPyPX)Rh(PR 3)] (3) complex with CO and is remarkably resistant to loss of either ligand. X-ray crystallographic analysis of complex 4b (R=Et) reveals an unusual cisoid coordination of the PCP phospbine ligands. These observations are supported by density functional theory (DFT) calculations. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.