Theoretical studies on ammonia borane dehydrogenation catalyzed by iron pincer complexes

Abstract

Catalytic dehydrogenation of ammonia borane by a series of iron bis(phosphinite) pincer complexes, such as [2,6-(Me2PO)2C6H3]Fe(H)(PMe3)2, [2,6-(Me2PO)2C6H3]Fe(H)(PMe2Ph)2, and [2,6-(Me2PO)2-4-(MeO)C6H2]Fe(H)(PMe2Ph)2, have been examined theoretically. Calculation of the energy diagram for the catalytic reaction steps using these catalysts showed that the rate-determining step is different for each ligand. The calculations also revealed that NH2BH2 is likely to be eliminated before H2 release because of the electrostatic repulsion between bulky ligands. Moreover, the electron-donating groups of the ligands stabilize the intermediate and transition states. The difference between the catalytic activities in this series of complexes can be explained by the above effects caused by changes in the ligands.