LAUSR

Abstract Nine Ni(II)-NHC complexes of the type [CpNiBr(NHC)], each containing either a symmetric or asymmetric alkyl/benzyl/phenylethyl imidazolium ligand, effectively catalysed the anaerobic oxidation of a series of secondary alcohols, including 1-phenylethanol to yield acetophenone. Catalytic reactions performed using KO t Bu as a mild base and 1,2-dibromobenzene as both oxidant and solvent cleanly converted secondary alcohols to their corresponding ketones in high yield using conventional heating, and almost quantitatively using microwave heating. Catalytic activity of the nine [CpNiBr(NHC)] complexes were evaluated separately under optimized conditions, where the more electron-donating NHC-bearing Ni complexes ( 1 , 2 , and 5 ) proved to be more efficient than the electron-witdrawing NHC ligand analogues ( 6 , 8 , and 9 ). Substrate screening studies revealed that secondary alcohols bearing electron-withdrawing functional groups were less efficiently oxidized. Catalyst concentration optimization studies were aimed at finding a catalyst concentration to limit the effects of catalyst deactivation, while also maintaining reasonable TONs. Additional characterization of selected Ni(II) complexes have been included, comprising three single crystal X-ray structure determinations, and a DFT study on the mechanistic reaction pathways of the alcohol oxidation reaction as well as α-ketone arylation, a potential secondary competitive catalytic reaction.