Tail-to-Tail Dimerization of Acrylonitrile Catalyzed by Low-Valent Ruthenium Complexes

Abstract

Abstract Zero-valent ruthenium complexes, [Ru(cod)(cot)] and [Ru(cod)(benzene)], are effective catalyst precursors for the tail-to-tail dimerization of acrylonitrile. Hydrogen pressure is necessary for the catalytic reaction, and the turnover number for dimers is greatly improved in neat acrylonitrile. Under the conditions of 150 °C and 25 atm of H2 (initial pressure at room temperature), the conversion of acrylonitrile is 61% and the yield of tail-to-tail dimers is 42% (selectivity 69%) in 3 h. The turnover number for the dimers is 2060, which is much higher than those reported so far. From the results of a catalytic reaction under D2 pressure, a reaction mechanism is proposed, in which two successive insertions of acrylonitrile into dihydridoruthenium complex are involved. A fast and reversible insertion of the third acrylonitrile is responsible for the H–D exchange of acrylonitrile in the deuterium labeling experiment.