[FeFe]-Hydrogenase Mimic Employing κ 2 - C , N -Pyridine Bridgehead Catalyzes Proton Reduction at Mild Overpotential

Two novel κ - , -pyridine bridged [FeFe]-H ase mimics ( and ) have been prepared and are shown to function as efficient molecular catalysts for electrocatalytic proton reduction. The elemental and structural composition of the complexes are confirmed by NMR and IR spectroscopy, high-resolution mass spectrometry and single-crystal X-ray diffraction. Electrochemical investigations reveal that the complexes reduce protons at their first reduction potential, resulting in the lowest overpotential (120 mV) ever reported for [FeFe]-H ase mimics in proton reduction catalysis when mild acid (phenol) is used as proton source.