The unique diiron catalytic unit that exists in the active site of the [FeFe]-H2ase has obvious design features that have been exploited in the development of hydrogen processing catalysts utilizing earth abundant metals, nickel and iron. In particular, the pendant base feature within the bridging dithiolate has been adapted within a nickel-diphosphinocyclohexane-like ring providing a remarkable catalyst for H2 prodn.(Helm, Dubois, et al., Science, 2011 , 863-866) We will describe modifications of the (μ-S(CH2)3S)[Fe(CO)3]2 p..
