Synthesis of achiral NCN pincer Pt(II) and Pd(II) complexes and catalytic application in the Suzuki-Miyaura reaction

Abstract

A series of platinum and palladium pincer complexes supported by achiral 1,3-bis(2′-imidazolinyl)benzene-based NCN ligands have been prepared via direct C2 metalation. Meanwhile, ligand precursor 3b and Pt(II) complex 4b were characterized by crystallographic studies, which reveals that the platinum atom in 4b adopts a distorted-square-planar geometry. The Pd(II) pincer complexes 5b was found to be an efficient catalyst for Suzuki cross-coupling reaction of aryl bromides and phenylboronic acid under air. In the presence of 0.5 mol% of Pd(II) 5b in DMF/K3PO4·3H2O for 8 h, the corresponding biaryl products could be obtained in 24–99% yields.