A family of novel cationic ruthenium pincer complexes: Synthesis, characterization and catalytic activity in the transfer hydrogenation of ketones

A family of novel cationic ruthenium complexes [RuHL(PAr3)2]Cl (Ar = phenyl, p-methoxyphenyl, and p-trifluoromethylphenyl; L = 2,6-bis(1,5-diphenyl-1H-pyrazol-3-yl)pyridine) has been synthesized and characterized by IR, 31P{1H} NMR, 1H NMR and elemental analyses. The [RuHL(PPh3)2]Cl was further identified by X-ray crystallography. These complexes exhibit good to excellent catalytic activities for the transfer hydrogenation of ketones in refluxing 2-propanol, and the highest TOF is up to 3534 h− 1. The effect of electronic factors of these complexes on the transfer hydrogenation of ketones reveals that the catalytic activity is promoted by the electron-withdrawing phosphine.