An Iridium(IV) Species, [Cp*Ir(NHC)Cl]+, Related to a Water-Oxidation Catalyst
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- 作者：Timothy P. Brewster ; James D. Blakemore ; Nathan D. Schley ; Christopher D. Incarvito ; Nilay Hazari ; Gary W. Brudvig ; Robert H. Crabtree
- 刊名：Organometallics
- 出版年：2011
- 出版时间：March 14, 2011
- 年：2011
- 卷：30
- 期：5
- 页码：965-973
- 全文大小：927K
- 年卷期：v.30,no.5(March 14, 2011)
- ISSN：1520-6041
文摘
The Ir precatalyst (3) contains both a Cp* and a 魏2C2,C2鈥?/sup>-1,3-diphenylimidazol-2-ylidene ligand, a C鈭扖 chelate, where one C donor is the NHC and the other is a cyclometalated N-phenyl wingtip group. The structure of 3 was confirmed by X-ray crystallography. Like our other recently described Cp*Ir catalysts, this compound is a precursor to a catalyst that can oxidize water to dioxygen. Electrochemical characterization of the new compound shows that it has a stable iridium(IV) oxidation state, [Cp*IrIV(NHC)Cl]+, in contrast with the unstable Ir(IV) state seen in our previous cyclometalated [Cp*IrIII(2-pyridyl-2鈥?phenyl)Cl] catalyst. The new iridium(IV) species has been characterized by EPR spectroscopy and has a rhombic symmetry, a consequence of the ligand environment. These results both support previous studies which suggest that Cp*Ir catalysts can be advanced through the relevant catalytic cycle(s) in one-electron steps and help clarify the electrochemical behavior of this class of water-oxidation catalysts.