TAIL-TO-TAIL DIMERIZATION OF ACRYLONITRILE CATALYZED BY LOW-VALENT RUTHENIUM COMPLEXES

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 rea ction, and the turnover number for dimers is greatly improved in neat acrylonitrile. Under the conditions of 150 degrees C and 25 atm of H-2 (initial pressure at room temperature), the conversion of acrylonitri le 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 hi gher than those reported so far. From the results of a catalytic react ion under D-2 pressure, a reaction mechanism is proposed, in which two successive insertions of acrylonitrile into dihydridoruthenium comple x are involved. A fast and reversible insertion of the third acrylonit rile is responsible for the H-D exchange of acrylonitrile in the deute rium labeling experiment.