Hong Soon Hyeok, Wenzel Anna G, Salguero Tina T, Day Michael W, Grubbs Robert H
Arnold and Mabel Beckman Laboratory of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
J Am Chem Soc. 2007 Jun 27;129(25):7961-8. doi: 10.1021/ja0713577. Epub 2007 Jun 5.
The decomposition of a series of ruthenium metathesis catalysts has been examined using methylidene species as model complexes. All of the phosphine-containing methylidene complexes decomposed to generate methylphosphonium salts, and their decomposition routes followed first-order kinetics. The formation of these salts in high conversion, coupled with the observed kinetic behavior for this reaction, suggests that the major decomposition pathway involves nucleophilic attack of a dissociated phosphine on the methylidene carbon. This mechanism also is consistent with decomposition observed in the presence of ethylene as a model olefin substrate. The decomposition of phosphine-free catalyst (H2IMes)(Cl)2Ru=CH(2-C6H4-O-i-Pr) (H2IMes = 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene) with ethylene was found to generate unidentified ruthenium hydride species. The novel ruthenium complex (H2IMes)(pyridine)3(Cl)2Ru, which was generated during the synthetic attempts to prepare the highly unstable pyridine-based methylidene complex (H2IMes)(pyridine)2(Cl)2Ru=CH2, is also reported.
已使用亚甲基物种作为模型配合物研究了一系列钌复分解催化剂的分解情况。所有含膦的亚甲基配合物均分解生成甲基鏻盐，且它们的分解途径遵循一级动力学。这些盐在高转化率下的形成，以及该反应观察到的动力学行为，表明主要分解途径涉及解离的膦对亚甲基碳的亲核攻击。该机制也与在作为模型烯烃底物的乙烯存在下观察到的分解情况一致。发现无膦催化剂(H2IMes)(Cl)2Ru=CH(2-C6H4-O-i-Pr)（H2IMes = 1,3-二甲基苯基-4,5-二氢咪唑-2-亚基）与乙烯分解生成未知的氢化钌物种。还报道了在合成极不稳定的吡啶基亚甲基配合物(H2IMes)(pyridine)2(Cl)2Ru=CH2的尝试过程中生成的新型钌配合物(H2IMes)(吡啶)3(Cl)2Ru。
