Ruthenium(II) Picolyl-NHC Complexes: Synthesis, Characterization, and Catalytic Activity in Amine N-alkylation and Transfer Hydrogenation Reactions

Ruthenium(II) p -cymene complexes with picolyl-functionalized N-heterocyclic carbenes [(η 6 - p -cymene)Ru( L )(Cl)][PF 6 ] ( L = 3-methyl-1-(2-picolyl)imidazol-2-ylidene ( 1a ), 3-isopropyl-1-(2-picolyl)imidazol-2-ylidene ( 1b ), 3,4,5-trimethyl-1-(2-picolyl)imidazol-2-ylidene ( 1c ), 3-mesityl-1-(2-picolyl)imidazol-2-ylidene ( 1d ), 3-methyl-1-(2-picolyl)benzoimidazol-2-ylidene ( 1e ), 3-methyl-1-(2-picolyl)-4,5-dichloroimidazol-2-ylidene ( 1f ), 3-phenyl-1-(2-picolyl)imidazol-2-ylidene ( 1g )) have been synthesized and characterized. Compounds 1a – g were recrystallized, and X-ray crystal structures are reported for 1a, f . Furthermore, compounds 1a – f show catalytic activity in transfer hydrogenation of ketones and N-alkylation of amines. Notably, complexes 1a, c, f were found to be very efficient and versatile catalysts toward transfer hydrogenation of a wide range of ketones and imines in addition to N-alkylation of several amines.