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

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 [PdCl2(L)2] (L = dibenzo[d,f][1,3,2]dioxaphosphepin, 6-phenoxy), C,P-chelate bonded monophosphite palladium complex 2 [Pd(κ2-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.

Graphical abstractA triad of novel phosphite Pd complexes derived from 2,2′-biphenol-based phosphites were synthesized. The application of a novel phosphite pincer Pd complex as pre-catalyst in C–P cross-coupling reactions of diphenylphosphine-borane with various aryl iodides is reported with a wide functional group tolerance and moderate to excellent isolated yields.Figure optionsDownload full-size imageDownload as PowerPoint slide