Lavallo Vincent, Grubbs Robert H
Arnold and Mabel Beckman Laboratory of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
Science. 2009 Oct 23;326(5952):559-62. doi: 10.1126/science.1178919.
Compared with the enormous arsenal of catalysts used to produce organic compounds, complementary species that are able to mediate sophisticated organometallic transformations are virtually nonexistent. We found that stable N-heterocyclic carbenes (NHCs) can mediate unusual organometallic transformations in solution at room temperature. Depending on the choice of NHC initiator, stoichiometric or catalytic reactions of bis(cyclooctatetraene)iron [Fe(COT)2] ensue. The stoichiometric reaction leads to the isolation of a previously unknown mixed-valent species, featuring distinct and directly bonded Fe(0) and Fe(I) centers. In the catalytic process, three iron atoms are fused to afford the tri-iron cluster Fe3(COT)3, which is a hydrocarbon analog of Dewar's classic Fe3(CO)12 complex. The key step in both of these processes is proposed to involve the NHC's ability to induce metal-metal bond formation. These NHC-mediated reactions provide a foundation on which to develop future organometallic transformations that are catalyzed by organic species.
与用于生产有机化合物的大量催化剂相比，能够介导复杂有机金属转化的互补物种几乎不存在。我们发现，稳定的N-杂环卡宾（NHC）能够在室温下的溶液中介导异常的有机金属转化。根据NHC引发剂的选择，双（环辛四烯）铁[Fe（COT）2]会发生化学计量反应或催化反应。化学计量反应导致分离出一种以前未知的混合价物种，其具有独特且直接键合的Fe（0）和Fe（I）中心。在催化过程中，三个铁原子融合形成三铁簇Fe3（COT）3，它是杜瓦经典Fe3（CO）12配合物的烃类类似物。这两个过程中的关键步骤被认为涉及NHC诱导金属-金属键形成的能力。这些NHC介导的反应为未来开发由有机物种催化的有机金属转化奠定了基础。
