| Budget Amount *help |
¥15,400,000 (Direct Cost: ¥15,400,000)
Fiscal Year 2006: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 2005: ¥13,200,000 (Direct Cost: ¥13,200,000)
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| Research Abstract |
Synthetic catalysts inspired by the extraordinary efficiency of nature's enzymes are revolutionizing chemical processing. Hydrogenase enzymes, for example, serve as models for developing new catalysts that one day could be the workhorses for producing hydrogen as a fuel or for hydrogenating carbon dioxide into hydrocarbon fuels. In one of the latest developments in this arena, Seiji Ogo and coworkers report the first catalytically active nickel-ruthenium complex that closely resembles an active site in hydrogenases (Science 2007,316,585). Hydrogenases are bacterial enzymes that catalyze cleavage of H_2 into two hydrogen ions and two electrons. There are two major classes of the enzymes : one type has an iron-iron active site and the second type has nickel-iron active site. Chemists have had some success in preparing catalytically active synthetic mimics of the diiron case, but a catalytically active mimic of the Ni-Fe active site, which contains the distinctive feature of a hydride ligand bridging between the two metal centers, has not been reported until now. One of the difficulties has been introducing the hydride ligand into the catalyst structure, writes Thomas B. Rauchfuss of the University of Illinois, Urbana-Champaign, in a Science commentary. "Faithful structural replicas of the Fe-Ni active site are known, but they are not catalytically active, in part because they lack the hydride ligand," he notes. Ogo and coworkers created their successful hydrogenase mimic by combining nickel dithiolate and ruthenium aqua building blocks-Ni(S_2N_2) and Ru(C_6Me_6)(OH_2)_3^<2+>, where Me is methyl. The ruthenium fragment serves as a stand-in for the Fe(CN)_2CO building block used by other researchers. This Ni-Ru complex is unique, Rauchfuss points out, because unlike other Ni-Fe complexes its "resting" form undergoes the crucial reaction with H_2 to give the bridging hydride active form.
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