An Iridium(IV) Species, [Cp*Ir(NHC)Cl]+, Related to a Water-Oxidation Catalyst
An Iridium(IV) Species, [Cp*Ir(NHC)Cl]+, Related to a Water-Oxidation Catalyst
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DOI：
10.1021/om101016s
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发表时间：
2011-03-14
期刊：
影响因子：
2.8
通讯作者：
Crabtree, Robert H.
中科院分区：
文献类型：
--
作者：
Brewster, Timothy P.;Blakemore, James D.;Crabtree, Robert H.
Ir预催化剂（3）含有Cp* 和kappa C-2（2），C-2 '-1，3-二苯基咪唑-2-亚基配体，C-C螯合物，其中一个C供体是NHC，另一个是环化的N-苯基翼尖基团。3的结构通过X射线晶体学证实。与我们最近描述的其他Cp*Ir催化剂一样，该化合物是可以将水氧化为分子氧的催化剂的前体。新化合物的电化学表征表明，它具有稳定的铱（IV）氧化态，[Cp*Ir-IV（NHC）Cl]（+），与我们以前的环化[Cp*Ir-III（2-吡啶基-2 '-苯基）Cl]催化剂中观察到的不稳定的Ir（IV）状态形成对比。新的铱（IV）物种的特征在于EPR光谱，并具有菱形对称性，配体环境的后果。这些结果都支持以前的研究表明，Cp*Ir催化剂可以通过相关的催化循环在单电子步骤，并帮助澄清这类水氧化催化剂的电化学行为。
The Ir precatalyst (3) contains both a Cp* and a kappa C-2(2),C-2'-1,3-diphenylimidazol-2-ylidene ligand, a C-C 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*Ir-IV(NHC)Cl](+), in contrast with the unstable Ir(IV) state seen in our previous cyclometalated [Cp*Ir-III(2-pyridyl-2'-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.