Nickel(II) complex incorporating methylene bridged tetradentate dicarbene ligand as an efficient catalyst toward CC and CN bond formation reactions

• Published in: Journal of molecular catalysis. A, Chemical Vol. 397; pp. 56 - 67
• Main Authors: Nirmala, Muthukumaran, Prakash, Govindan, Ramachandran, Rangasamy, Viswanathamurthi, Periasamy, Malecki, Jan Grzegorz, Linert, Wolfgang
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-02-2015
• Subjects: C[sbnd]N coupling reaction; Dianionic bis(aryloxy-NHC) ligand; Ni-NHC complex; Suzuki–Miyaura; X-ray diffraction; Ni-NHC complex; X-ray diffraction; CN coupling reaction; Suzuki–Miyaura; Dianionic bis(aryloxy-NHC) ligand
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2014.10.031

A new air-stable nickel(II) complex containing dianionic bis(aryloxy-NHC) ligand was synthesized and structurally characterized. The Ni complex possesses a square planar geometry with the ligand coordinating through bi-negative tetradentate C2O2 fashion. The new complex was found to be an efficient catalyst toward CC and CN bond formation reactions.
•A new nickel(II) dicarbene complex has been synthesized and characterized.•X-ray studies revealed a square planar geometry of the new complex.•The new complex catalyzes the Suzuki–Miyaura cross-coupling reaction effectively.•The Ni(II) complex also efficiently catalyzes the amination of aryl chlorides.
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.