PNNL

Abstract

A series of iron hydride complexes featuring PRNR'PR (PRNR'PR = R2PCH2N(R')CH2PR2 where R = Ph, R' = Me; R = Et, R' = Ph, Bn, Me, tBu) and cyclopentadienyl (CpX = C5H4X where X = H, C5F4N) ligands has been synthesized, characterized by NMR spectroscopy, X-ray diffraction and cyclic voltammetry, and examined by quantum chemistry calculations. Each compound was tested for the electrocatalytic oxidation of H2 and the most active complex, (CpC5F4N)Fe(PEtNMePEt)(H), exhibited a turnover frequency of 8.6 s-1 at 1 atm of H2 with an overpotential of 0.41 V, as measured from the half peak potential of the catalytic wave. Control complexes that do not contain pendant amine groups were also prepared and characterized, but no catalysis was observed. This work demonstrates the importance of the pendant amine in facilitating heterolytic H2 cleavage and subsequent proton movement necessary for electrocatalytic H2 oxidation. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.