Conformational Flexibility in a Carbobicyclic Diphosphinite Ligand

Abstract

AbstractAn unsymmetrical bicyclo[3.2.0]heptanyl diphosphinite ligand, FLEXIphosO, shows flexible coordination modes to palladium centres. The X‐ray crystal structure for [Pd02(P,P′)3] has been determined which reveals that the bicyclic backbone of the FLEXIphosO ligand exists in an exo‐envelope conformation. The change in conformation stands in stark contrast to that observed in mononuclear neutral and cationic palladium(II) complexes containing the FLEXIphosO ligand, where an endo‐envelope is observed in solution and in the solid‐state. Theoretical studies provide an insight into the relative stability of palladium(0) complexes containing the FLEXIphosO ligand. Another large spanning angle ligand, SPANphos, does not form a similar palladium(0) dimer complex under identical reaction conditions, highlighting the unusual behaviour of the FLEXIphosO ligand.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)