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1973年以来,各国许多学者提出了各自不同的固氮酶活化模型和作用机理。但都是考虑Mo原子既是吸附分子氮的中心,又是还原氮的中心。他们的设想主要建立在模型化合物体系还原氮成功的基础上。我们分析了Mo在固氮酶中价态,根据实验结果推测应为Mo(111)。从配位化合物取代反应理论考虑,Mo(111)为惰性反应。不宜作活化氮吸附中心。此外,我们又分析了固氮酶和钼铁硫簇化合物的许多性质。提出固氮酶催化还原底物应有双中心机理协同完成。一个是由二个Fe原子组成的吸附N_2中心,另一个是钼铁硫原子簇组成的电子还原中心。讨论了反应速率的决定步骤是电子传送。对固氮酶中Fe作底物吸附中心的可能性罗列了大量实验结果进行论证。并讨论了氮分子在二个Fe之间η_2吸附方式对活化氮最有利。用双中心机理顺利地解释了固氮酶的各种反应性。
Since 1973, many scholars from different countries have put forward different models and mechanism of nitrogenase activation. But both consider the Mo atom is not only the center of adsorbed molecular nitrogen, but also the center of reducing nitrogen. Their idea is based primarily on the success of the model compound system in reducing nitrogen. We analyzed the valence state of Mo in nitrogenase, which is supposed to be Mo (111) according to the experimental results. Mo (111) is an inert reaction from the theory of coordination reaction of coordination compounds. Not suitable for activated nitrogen adsorption center. In addition, we analyzed many of the properties of nitrogenase and molybdenum iron-sulfur cluster compounds. It is proposed that nitrogen-catalyzed catalytic reduction should be accomplished by a dual-center mechanism. One is composed of two Fe atoms composed of N 2 centers and the other is an electron reduction center composed of clusters of molybdenum iron and sulfur atoms. It is discussed that the decision step of the reaction rate is electron transfer. The possibility of Fe as a substrate adsorption center for nitrogenase is listed in a large number of experimental results. It is also discussed that the η_2 adsorption mode between nitrogen and nitrogen in two Fe is the most favorable for activated nitrogen. The bivariate mechanism successfully explained the various reactivity of nitrogenase.