Application of Ni(II) complexes of air stable Schiff base functionalized <i>N</i>-heterocyclic carbene ligands as catalysts for the transfer hydrogenation of aliphatic ketones

2018-09-19T13:04:53Z (GMT) by Samaila Abubakar Muhammad D. Bala
<p>New air stable <i>N</i>-heterocyclic carbene functionalized Schiff base ligands (L) of the type 2-[-2-[3-(R)imidazol-1-yl]ethyliminomethyl]phenol [R = methyl (<b>2</b>), 2-pyridylmethyl (<b>3</b>)] were synthesized and characterized by NMR, IR, MS, and CHN analysis. Single crystal X-ray structural analysis of their Ni(II) complexes revealed square planar arrangement of the chelating ligands coordinated in tridentate (<b>2</b>, C^N^O) and tetradentate (<b>3</b>, N^C^N^O) modes around the metal. The three new isolated and fully characterized complexes were utilized as catalysts for the catalytic transfer hydrogenation of aliphatic ketones in 2-propanol as solvent and source of hydrogen. Based on 0.2 mol% catalyst concentration, the complexes showed activity for aliphatic ketones and 100% conversion (turnover number of 500) for cyclohexanone and all the aromatic ketones tested.</p>