Facile Synthesis of Highly Congested 1,2-Diphosphinobenzenes from Bis(phosphine)boronium Salts

Bis(phosphine)boronium salts 3a−c were designed and prepared as key building blocks for the synthesis of highly congested diphosphinobenzenes. The preparation of sterically hindered ortho-phenylene-bridged diphosphines 1a−c was achieved by the reaction of the bis(phosphine)boronium salts 3a−c with difluorobenzenechromium complex 2 and subsequent removal of the BH2 group. The steric nature of diphosphine 1a was revealed in single-crystal X-ray analysis of its Rh complex.