Oxidative C–C Bond Formation Reactivity of Organometallic Ni(II), Ni(III), and Ni(IV) Complexes

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• 作者：Michael B. Watson ; Nigam P. Rath ; Liviu M. Mirica
• 刊名：Journal of the American Chemical Society
• 出版年：2017
• 出版时间：January 11, 2017
• 年：2017
• 卷：139
• 期：1
• 页码：35-38
• 全文大小：321K
• ISSN：1520-5126

文摘

The use of the tridentate ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (Meb>3b>tacn) and the cyclic alkyl/aryl C-donor ligand -CHb>2b>CMeb>2b>-o-Cb>6b>Hb>4b>- (cycloneophyl) allows for the synthesis of isolable organometallic Ni^II, Ni^III, and Ni^IV complexes. Surprisingly, the five-coordinate Ni^III complex is stable both in solution and the solid state, and exhibits limited C-C bond formation reactivity. Oxidation by one electron of this Ni^III species generates a six-coordinate Ni^IV complex, with an acetonitrile molecule bound to Ni. Interestingly, illumination of the Ni^IV complex with blue LEDs results in rapid formation of the cyclic C-C product at room temperature. This reactivity has important implications for the recently developed dual Ni/photoredox catalytic systems proposed to involve high-valent organometallic Ni intermediates. Additional reactivity studies show the corresponding Ni^II species undergoes oxidative addition with alkyl halides, as well as rapid oxidation by Ob>2b>, to generate detectable Ni^III and/or Ni^IV intermediates and followed by C-C bond formation.