Nickel-ruthenium-based complexes as biomimetic models of [NiFe] and [NiFeSe] hydrogenases for dihydrogen evolution.

The two heterodinuclear nickel-ruthenium complexes [Ni(xbSmS)RuCp(PPh)]PF and [Ni(xbSmSe)RuCp(PPh)]PF (HxbSmS = 1,2-bis(4-mercapto-3,3-dimethyl-2-thiabutyl)benzene, HxbSmSe = 1,2,-bis(2-thiabutyl-3,3-dimethyl-4-selenol)benzene, Cp = cyclopentadienyl) were synthesized as biomimetic models of [NiFe] and [NiFeSe] hydrogenases. The X-ray structural analyses of the complexes show that the two NiRu complexes are isomorphous; in both NiRu complexes the nickel(ii) centers are coordinated in a square-planar environment with two thioether donor atoms and two thiolate or selenolate donors that are bridging to the ruthenium(ii) center. The Ru(ii) ion is further coordinated to a η-cyclopentadienyl group and a triphenylphosphane ligand.

Electrocatalytic proton reduction by a model for [NiFeSe] hydrogenases.

Two new heterodinuclear nickel-iron complexes [Ni(pbSmSe)FeCpCO]PF and [Ni(xbSmSe)FeCpCO]PF were synthesized as mimics of the [NiFeSe] hydrogenase active site (HCp = cyclopentadiene; HpbSmSe = 1,9-diselenol-3,7-dithia-2,2,8,8-tetramethylnonane; HxbSmSe = 1,2,-bis(2-thiabutyl-3,3-dimethyl-4-selenol)benzene). The compounds were characterized by single crystal X-ray diffraction and cyclic voltammetry. X-ray structure determinations showed that in both NiFe complexes the nickel(ii) center is in a square-planar SSe environment; the two selenolate donors are bridging to the iron(ii) center that is further coordinated to an η-cyclopentadienyl group and a carbon monoxide ligand.