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前言形成过渡金属络合物是活化惰性分子最有效和最普遍的方法之一。络合的结果,改变了配位体的反应活性,创造了有利的反应空间条件,从而使我们能够实现在过渡金属络合物影响下的许多催化反应。有两个重要的生物过程:光合作用和固氮,长久以来就引起化学工作者的注意。大气中的分子氮(N_2)——通过生物固氮或工业合成氨——是地球上合成含氮化合物的唯一来源;而二氧化碳(CO_2)则是所有有生命物质的唯一碳源。因此,光合作用和生物固氮是地球上提供生命的两大过程。化学工作者正在努力创造类似的纯化学过程来模拟生物固氮和光合作用。近十年来,N_2与过渡金属化合物的反应已进行了广泛的研究。自从十年前 Allen 和 Senoff 制备了第一个分子氮络合物以来,到目前已成功地合成了一百多个过渡金属分子氮络合物。另一方面,N_2可以在温和条件下,在过渡金属化合物存在下还原,水解之后产生氨或肼。但是,现在的化学固氮体系,在固氮效果方面还远不能与固氮酶相比。迄今,对生物固氮的还原机理尚在研究中。最近,Chatt 报导,单金属络合的分子氮络合物[M(N_2)_2(PR_3)_4](M=Mo 或 W;R=烷基或芳基),在质子环境中,温和条件下,以高达90%的产率还原为 NH_3。这一反应对于我们了解固
Introduction The formation of transition metal complexes is one of the most effective and common ways to activate inert molecules. As a result of the complexing, the reactivity of the ligand is changed, creating a favorable reaction space condition so that we can achieve many catalytic reactions under the influence of the transition metal complex. There are two important biological processes: photosynthesis and nitrogen fixation, which have long drawn chemists’ attention. Molecular nitrogen (N2) in the atmosphere - through biological nitrogen fixation or industrial ammonia synthesis - is the only source of synthetic nitrogenous compounds on Earth; and carbon dioxide (CO2) is the only carbon source for all living matter. Therefore, photosynthesis and biological nitrogen fixation are two major processes that provide life on Earth. Chemists are working to create similar pure chemical processes to mimic biological nitrogen fixation and photosynthesis. In recent ten years, the reaction of N 2 with transition metal compounds has been extensively studied. Since Allen and Senoff prepared the first molecular nitrogen complex a decade ago, so far, more than one hundred transition metal molecular nitrogen complexes have been successfully synthesized. On the other hand, N 2 can be reduced under mild conditions in the presence of a transition metal compound to produce ammonia or hydrazine after hydrolysis. However, the current chemical nitrogen fixation system is far from being able to compare nitrogen fixation with nitrogen fixation. Up to now, the mechanism of biological nitrogen fixation is still under study. Recently, Chatt reported that the monometallic complexed molecular nitrogen complex [M (N_2) _2 (PR_3) _4] (M = Mo or W; R = alkyl or aryl) , Reduced to NH 3 with up to 90% yield. This reaction to our understanding of solid