CH(2) Linkage Effects on the Reactivity of Bis(aminophosphine)–Ruthenium Complexes for Selective Hydrogenation of Esters into Alcohols

A novel ruthenium complex binding to two subtly different aminophosphine ligands, (o-PPh(2)C(6)H(4)CH(2)NH(2))(o-PPh(2)C(6)H(4)NH(2))RuCl(2), was successfully isolated. This bis(aminophosphine)–ruthenium complex shows efficient activity in both dimethyl oxalate (DMO) and methyl benzoate (MB) hydrogenation. On the contrast, similar complexes (o-PPh(2)C(6)H(4)NH(2))(2)RuCl(2) and (o-PPh(2)C(6)H(4)CH(2)NH(2))(2)RuCl(2), can only effectively catalyze the hydrogenation of DMO and MB, respectively. Our experimental studies in combination of theoretical calculations reveal that the remarkable substrate selectivity in the hydrogenation of esters arises from the nonbonding interactions operated by the CH(2) linkage of the ligand.