Department of Chemistry & Catalysis Research Center, Molecular Catalysis, Technische Universität München, Lichtenbergstr. 4, D-85747 Garching bei München, Germany.
Dalton Trans. 2018 Dec 18;48(1):79-89. doi: 10.1039/c8dt03713b.
The cationic abnormal N-heterocyclic carbene complex [Ru(OAc)(dppe)(PC)]Br (2b) (PC = bidentate phosphine-carbene ligand) has been obtained by treatment of the neutral derivative RuBr(OAc)(PPh3)(PC) (2a) with dppe in THF. Reaction of 2b with Ag2O afforded the heterobimetallic complex Ru(OAc)(dppe)(PC)AgBr (2c) which can be easily transmetallated with [Ir(cod)Cl]2 giving Ru(OAc)(dppe)(PC)IrCl(cod) (2d). Similarly, [{Ru(OAc)(PC)(PC')}2Ag][AgBr2] (1b) reacts with [Ir(cod)Cl]2 with formation of Ru(OAc)(PC)(PC')IrCl(cod) (1e). All complexes were characterized by NMR in solution and by single crystal X-ray diffraction studies in solid state. For the cationic complexes the 1H NMR resonance of the carbene-proton is considerably down-field shifted (δ > 9 ppm) with respect to that of the neutral derivatives. Cyclic voltammetry and differential pulse voltammetry studies show that the Ru-centered redox process occurs at lower potential (ΔE > 100 mV) after transmetallation with iridium, suggesting an interaction of the two metals along the π-system of the heterocycle ligand. These complexes display catalytic activity in transfer hydrogenation of acetophenone in 2-propanol with a significant influence of Ir and Ag centers on the Ru moiety. The synthesis of the imidazolyl-based N-heterocyclic dicarbene Ru-Ir complexes, which entails the easy metallation of the reactive cationic abnormal N-heterocyclic carbene Ru complexes with Ag2O, represents a suitable pathway for the preparation of heterometallic ruthenium complexes.
阳离子异常 N-杂环卡宾配合物[Ru(OAc)(dppe)(PC)]Br（2b）（PC=双齿膦-卡宾配体）通过中性衍生物 RuBr(OAc)(PPh3)(PC)（2a）与 dppe 在 THF 中的反应得到。2b 与 Ag2O 反应得到异双金属配合物 Ru(OAc)(dppe)(PC)AgBr（2c），该配合物可容易地与[Ir(cod)Cl]2 进行转金属化反应，得到 Ru(OAc)(dppe)(PC)IrCl(cod)（2d）。同样，[{Ru(OAc)(PC)(PC')}2Ag][AgBr2]（1b）与[Ir(cod)Cl]2 反应形成 Ru(OAc)(PC)(PC')IrCl(cod)（1e）。所有配合物均通过溶液中的 NMR 和固态中的单晶 X 射线衍射研究进行了表征。对于阳离子配合物，卡宾质子的 1H NMR 共振明显向磁场位移（δ>9 ppm）相对于中性衍生物。循环伏安法和差分脉冲伏安法研究表明，在与铱进行转金属化后，Ru 中心的氧化还原过程发生在较低的电位（ΔE>100 mV），表明两个金属沿杂环配体的π-体系相互作用。这些配合物在 2-丙醇中对苯乙酮的转移加氢反应中显示出催化活性，Ir 和 Ag 中心对 Ru 部分有显著影响。基于咪唑的 N-杂环二卡宾 Ru-Ir 配合物的合成，涉及对具有反应性阳离子异常 N-杂环卡宾 Ru 配合物的 Ag2O 的易金属化，代表了制备异金属钌配合物的合适途径。
