Diphosphirenium Salt: A New Versatile Ligand

Abstract

Strained aromatic cyclopropenylium cations are versatile ligands for transition metal complexes: η¹-, η ²- and η³-coordination modes have been observed. Here we report on the ligand properties of the related diphosphirenium salt A[1]. Treatment of a dichloromethane solution of diphosphirenium salt A with an equimolar amount of palladium tetrakis(mpheny1phosphine) afforded 1,3-diphospha-2-bis(uiphenyl-phosphine)pallada(II)cyclobutene B in 70% yield. Exchange of the triphenylphosphine ligands occurs with various phosphines, and the structures of these new diphospha-metallacyclobutenes have been elucidated by NMR and in one case by a single X-ray diffraction study [2].