Theoretical Study of the Gas-Phase Fe(CO)5 Catalyzed Water Gas Shift Reaction:  A New Mechanism Proposed

A novel mechanism for the gas-phase Fe(CO)(5) and base catalyzed water gas shift reaction has been examined. The reaction pathway described here is predicted at the B3LYP/6-31++G(d,p) level to be energetically competitive with the classic mechanism. The reaction path explored here involves the energetically barrierless formation of (CO)(4)FeCOOH(-) (the catalyst of the system) decarboxylation induced by the addition of CO to give (CO)(4)FeCHO, and evolution of H(2) upon addition of H(2)O to the (CO)(4)FeCHO intermediate. The energetic barriers predicted for the last two steps are 21.2 and 42.0 kcal/mol, respectively, using the B3LYP method.