Synthesis, Structures and Chemical Reactivity of Dithiolato-Bridged Ni-Fe Complexes as Biomimetics for the Active Site of [NiFe]-Hydrogenases

To develop the structural and functional modeling chemistry of [NiFe]-H(2)ases, we have carried out a study regarding the synthesis, structural characterization and reactivity of a new series of [NiFe]-H(2)ase model complexes. Thus, treatment of diphosphine dppb-chelated Ni complex (dppb)NiCl2 (dppb = 1,2(Ph2P)(2)C6H4) with (dppv)Fe(CO)(2)(pdt) (dppv = 1,2-(Ph2P)(2)C2H2, pdt = 1,3-propanedithiolate) and NaBF4 gave dicarbonyl complex [(dppb)Ni(pdt)Fe(CO)(2)(dppv)](BP4)(2) ([A](B-F-4)(2)). Further treatment of [A](BF4)(2) with Me3NO and Bu4NCN or KSCN afforded t-cyanido and t-isothiocyanato complexes [(dppb)Ni(pdt)Fe(CO)(t-R)(dppv)]BF4 ([1]BF4, R = CN; [2]BF4, R = NCS), respectively. While azadiphosphine MeN(CH2PPh2)(2)-chelated t-hydride complex [MeN(CH2PPh2)(2)Ni(pdt)Fe(CO)(t-H)(dppv)]BF4 ([3]BF4) was prepared by treatment of dicarbonyl complex [MeN-(CH2PPh2)(2)Ni(pdt)Fe(CO)(2)(dppv)](BF4)(2 )([B](BF4)(2)) with Me3NO and 1.5 MPa of H-2, treatment of dicarbonyl complex [B](BF4)(2) with Me3NO (without H-2) in pyridine resulted in formation of a novel monocarbonyl complex [MeN(CH2PPh2)(2)Ni(SCHCH2CH2S)Fe(CO)(dppv)]BF4 ([4]BF4) via the unexpected sp(3) C-H bond activation reaction. Furthermore, azadiphosphine PhN(CH2PPh2)(2)-chelated mu-mercapto complex [PhN(CH2PPh2)(2)Ni(pdt)Fe(CO)(mu-SH)(dppv)]BF4 ([5]BF4) was prepared by treatment of dicarbonyl complex [PhN(CH2PPh2)(2)Ni(pdt)Fe(CO)(2)(dppv)](BF4)(2) ([C](BF4)(2)) with Me3NO and H2S gas, whereas treatment of azadiphosphine Ph2CHN(CH2PPh2)(2)-chelated dicarbonyl complex [Ph2CHN(CH2PPh2)(2)Ni(pdoFe(CO)(2)(dppe)](BF4)(2) ([D](BF4)(2), dppe = 1,2-(Ph2P)(2)C2H4) with Me3NO center dot 2H(2)O gave rise to mu-hydroxo complex [Ph2CHN(CH2PPh2)(2)Ni(pdt)Fe(CO)(mu-OH)(dPPe)]BF4 ([6]BF4). All the possible pathways for formation of the new model complexes are briefly discussed, and their structures were fully characterized by various spectroscopic techniques and for six of them by X-ray crystallography.

Automated summary

This study focuses on the synthesis, structural characterization and reactivity of a new series of [NiFe]-H(2)ase model complexes, and discusses their possible formation pathways.