Synthetic analogues of the active sites of nitrogenase and [NiFe] hydrogenase

Abstract

Biological nitrogen fixation and H2 metabolism are mediated by nitrogenase and hydrogenase, respectively. Their active sites consist of complex transition-metal sulfide/thiolate clusters, which have been long-standing synthetic challenges. This account describes our synthetic approaches toward the active sites of nitrogenase and [NiFe] hydrogenase. A new class of iron-sulfur clusters modeling or structurally analogous to the nitrogenase metallo-clusters, namely P-cluster and FeMo-cofactor, have been synthesized from homogeneous self-assembly reactions of iron(II) amide or mesityl complexes with bulky thiols and elemental sulfur in toluene. A series of thiolate-bridged Fe-Ni complexes modeling the active site of [NiFe] hydrogenase have been synthesized via two ways: One is to use iron(II)-dithiolate complexes carrying CO and CN ligands as precursors to provide the (CO/CN)Fe-Ni complexes. The other way is to split a tetranuclear (CO)3Fe-Ni-Ni-Fe(CO)3 complex, which is available from a sequential reaction of [FeBr2(CO)4] with NaStBu and NiBr2(EtOH)4 at -40°C.