MOLYBDENUM CATALYZED CARBONYLATION OF ETHYLENE TO PROPIONIC-ACID AND ANHYDRIDE

We have discovered a low pressure and low temperature process for the single step conversion of ethylene and carbon monoxide to either propi onic acid or anhydride utilizing surprisingly active, inexpensive Cr g roup based catalysts which operate at very high rates under low-to-mod erate pressures (30-70 atm) and temperatures (150-200 degrees C). Mech anistic investigations of the Mo based process, which is clearly the m ost active metal of the group, imply that catalysis is initiated by a rate limiting CO dissociation from Mo(CO)(6). This dissociation appear s to be followed by a process which ultimately transfers an I atom fro m EtI to the coordinatively unsaturated Mo(CO)(5), probably via an inn er sphere, electron transfer process. Subsequent reaction of the resul tant ethyl radical with Mo(CO)(6) probably generates Very reactive odd electron Mo species which are capable of rapid catalysis via classica l olefin carbonylation mechanisms. This discovery represents the first case of an efficient carbonylation process based on the Cr group meta ls and a unique method for initiating carbonylation catalysis. A gener al description of this process and the mechanistic proposal, which is based on detailed kinetics, spectroscopy and model reactions, will be presented.