Pyrazolato-Bridged Dinuclear Complexes of Ruthenium(II) and Rhodium(III) with N-Heterocyclic Carbene Ligands: Synthesis, Characterization, and Electrochemical Properties

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• 作者：Stefan A. Reindl ; Alexander P枚thig ; Markus Drees ; Bettina Bechlars ; Eberhardt Herdtweck ; Wolfgang A. Herrmann ; Fritz E. K眉hn
• 刊名：Organometallics
• 出版年：2013
• 出版时间：August 12, 2013
• 年：2013
• 卷：32
• 期：15
• 页码：4082-4091
• 全文大小：504K
• 年卷期：v.32,no.15(August 12, 2013)
• ISSN：1520-6041

文摘

Pyrazolato-bridged dinuclear complexes of ruthenium and rhodium were synthesized from N-heterocyclic carbene (NHC) precursors, 3,5-bis[(methylimidazolium-1-yl)methyl]-1H-pyrazole bis(hexafluorophosphate), and the metal precursors [Ru(p-cymene)Cl₂]₂ and [Rh(畏⁵-C₅Me₅)Cl₂]₂. Depending on the reaction conditions, dinuclear bis(imidazolium) complexes or the corresponding bis(NHC) complexes were formed. These complexes were characterized by NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. The metal鈥搈etal distances are in the range 3.85鈥?.92 脜. Accordingly, a metal鈥搈etal bond can be excluded in all cases. The electronic properties were examined by cyclic voltammetry (CV) to detect possible electronic coupling between the metal centers. In the case of the imidazolium complexes irreversible processes are observed in CV, indicating decomposition. The Ru鈥揵is(NHC) complex鈥攃oordinatively saturated with six acetonitrile molecules instead of p-cymene ligands鈥攕hows three reversible redox processes. Density functional theory (DFT) calculations were used to verify the processes during CV. The Rh鈥揵is(NHC) complex decomposes through irreversible reductions.