Novel phosphite palladium complexes and their application in C–P cross-coupling reactions

Abstract

A mono- and a 1,3-bis-phosphite arene ligand based on 2,2′-biphenol have been synthesized in order to study the synthesis of the corresponding palladium(II) complexes starting from different Pd precursors. Novel bis-phosphite palladium complex 1 [PdCl 2(L) 2] (L = dibenzo[d,f][1,3,2]dioxaphosphepin, 6-phenoxy), C, P-chelate bonded monophosphite palladium complex 2 [Pd(κ 2-L)(μ-Cl)] 2, and PCP-pincer palladium complex 3 have been prepared from these ligands in promising to excellent yields (50–95%). Additionally, complexes 1 and 3 have been characterized by X-ray crystal structure determinations. The application of 2,6-bis-phosphite pincer palladium(II) complex 3 in C–P cross-coupling between diphenylphosphine-borane and a wide range of various aryl iodides under very mild conditions is reported. Kinetic investigations indicate that 3 merely acts as a pre-catalyst and that Pd nanoparticles are the actual catalytically active species.