Nickel(II) complex incorporating methylene bridged tetradentate dicarbene ligand as an efficient catalyst toward C[sbnd]C and C[sbnd]N bond formation reactions

Abstract

For the evaluation of binding and catalytic nature of N-heterocyclic carbenes (NHCs) and their complexes, a new methylene bridged bis(aryloxy-NHC) ligand has been prepared. A novel air-stable Ni(II) complex bearing the new NHC ligand has been synthesized and characterized by elemental analysis, NMR (1H and 13C) as well as ESI-mass spectrometry. The molecular structure of the complex was identified by means of single crystal X-ray diffraction analysis which revealed that the Ni(II) complex possesses a square planar geometry with the ligand coordinating with bi-negative tetradentate C2O2 fashion and the complex showed efficient catalytic activity toward the Suzuki–Miyaura cross-coupling reaction between aryl halides and arylboronic acids under phosphine free conditions. The new complex also catalyzed the amination of aryl chlorides in the presence of KOtBu. Various aryl chlorides and amines can react smoothly to give the corresponding aminated products in moderate to high yields. Both secondary and primary amines are well tolerated under the optimal reaction conditions.