Straightforward Access to Tetrametallic Complexes with a Square Array by Oxidative Dimerization of Organometallic Wires

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• 作者：Alexandre Burgun ; Fr茅d茅ric Gendron ; Phil A. Schauer ; Brian W. Skelton ; Paul J. Low ; Karine Costuas ; Jean-Fran莽ois Halet ; Michael I. Bruce ; Claude Lapinte
• 刊名：Organometallics
• 出版年：2013
• 出版时间：September 23, 2013
• 年：2013
• 卷：32
• 期：18
• 页码：5015-5025
• 全文大小：462K
• 年卷期：v.32,no.18(September 23, 2013)
• ISSN：1520-6041

文摘

The bimetallic ruthenium complex {Cp(dppe)Ru}₂(渭-C鈮C鈮C鈮) (3; Cp = cyclopentadienyl, dppe = 1,2-bis(diphenylphosphino)ethane) has been prepared and the molecular structure determined. The cyclic voltammogram of 3 is characterized by three reversible one-electron events with a large potential difference between the two first waves (螖E掳 = 0.44 V), indicating the large thermodynamic stability of the MV (mixed-valence) 3(PF₆), which can be considered as a class III MV complex. The complex 3(PF₆) was quantitatively prepared by treatment of 3 with 1 equiv of [FeCp₂](PF₆) at 鈭?8 掳C and characterized by EPR spectroscopy. Above 鈭?0 掳C, solutions of 3(PF₆) provide the asymmetric tetranuclear complex {cyclo-C([Ru])C(CCCC[Ru])C(CC[Ru])C(CC[Ru])}(PF₆)₂ (4(PF₆)₂; [Ru] = Cp(dppe)Ru) which was formed regiospecifically and isolated in 92% yield. Thus, despite the thermodynamic stability of the monocation radical 3(PF₆) as evidenced by the electrochemical data, and the extensively delocalized electronic structure, a slow dimerization reaction takes place, affording a stable, tetranuclear complex. The new compound was characterized by a single-crystal X-ray diffraction study, cyclic voltammetry, and multinuclear NMR, IR, UV鈥搗is, and near-IR spectroscopy, and the data were analyzed with the support of quantum chemical investigations at the DFT level of theory. The regiospecificity of the dimerization reaction is controlled by a balance of steric and electronic factors, which favors intermolecular (C_伪 + C_纬) radical coupling.