NITRILES AND HYDROGEN ON A NICKEL-CATALYST - THEORETICAL EVIDENCE OF A PROCESS COMPETING WITH THE TOTAL HYDROGENATION REACTION

Possible reaction steps occurring when nitriles and hydrogen are simul taneously adsorbed on nickel have been investigated by means of semi-e mpirical extended Huckel calculations. The study of the reactivity has been carried out on Ni(100): after the first hydrogenation step which principally yields imido ethylidene (CH3CH=N-), both adsorbed perpend icular and parallel to the metallic surface, we predict a competition between a second hydrogenation, which leads to a nitrene species (CH3C H2-N=) doubly bonded to the surface, and a coupling process involving a C-C bond formation. For each of these steps, activation energies hav e been estimated, and the stabilities of the a priori possible adsorbe d forms of the intermediates have been compared. (C) 1996 Academic Pre ss, Inc.