Mono- and binuclear ruthenium(II) complexes containing pyridine-2,6-diimine (Pydim) ligands: Synthesis, characterization and catalytic activity in the transfer hydrogenation of acetophenone

Abstract

A series of neutral mono- and binuclear Ru(II) complexes: [PydimCl 2RuL] (Pydim ( 1) pyridine-2,6-diimine; ( 2) L = NCMe; ( 3) L = PPh 3) and [PydimCl 2Ru(L-L)RuCl 2Pydim] ( 4) L-L = pyrazine; ( 5) L-L = 4,4′-bipyridine) have been synthesized from the corresponding ( p-cymene)ruthenium dichloride dimer, pydim and ancillary ligands L and L-L, respectively. The Pydim-Ru(II) complexes have been employed as catalysts for the transfer hydrogenation of acetophenone in the presence of KOH using 2-propanol as a hydrogen source. Ligand substitution studies indicate that there is a significant difference in reactivity between complexes containing L/L-L and Pydim. Yields of up to 93% were obtained after 5 min at 82 °C.