Organonickel complexes encumbering bis-imidazolylidene carbene ligands: Synthesis, X-ray structure and catalytic insights on Buchwald-Hartwig amination reactions

• Published in: Journal of organometallic chemistry Vol. 831; pp. 1 - 10
• Main Authors: Nirmala, Muthukumaran, Saranya, Gandhi, Viswanathamurthi, Periasamy, Bertani, Roberta, Sgarbossa, Paolo, Malecki, Jan Grzegorz
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-03-2017
• Subjects: C[sbnd]N coupling reaction; Diimidazolium NHC ligand; Ni[sbnd]NHC complexes; X-ray diffraction; X-ray diffraction; CN coupling reaction; NiNHC complexes; Diimidazolium NHC ligand
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/j.jorganchem.2016.12.029

New four coordinated homoleptic bis(diimidazolylidene)nickel(II) complexes (C1 & C2) were synthesized and characterized by elemental analysis, NMR (1H and 13C) as well as ESI-Mass spectrometry. The molecular structure of the complex C1 was identified by means of single-crystal X-ray diffraction analysis, which revealed that the complexes possess a distorted square planar geometry with chelating bis(diimidazolylidene) NHC ligands and two non coordinating bromide counter ions in tetradentate C4 fashion. A survey of their catalytic activity in Buchwald−Hartwig amination has been performed. The newly synthesized complexes 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. The scope of the reaction encompasses electronically varied aryl chlorides and nitrogen-containing heteroaryl chlorides, including pyridine and quinoline derivatives. Both secondary and primary amines are well tolerated under the optimal reaction conditions.
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•New homoleptic bis(diimidazolylidene)nickel(II) catalysts have been synthesized and characterized.•X-ray studies revealed distorted square planar geometry of the new complexes.•The new catalysts catalyze the Buchwald−Hartwig amination reactions effectively.