INVESTIGATIONS OF BIOMIMETIC NITROGEN FIXATION

阐明生物固氮的机理， 当代重大问题。 作为世界 人口继续增加健康和福祉的 人们依赖于充足的蛋白质食物 作为一个绝对必要的饮食要求。 长期 本研究的目的是阐明氨的作用机理 在N2的仿生还原中形成并发展 用于生产氨和 肼。 为了实现这些目标，本研究将调查 仿生系统中氨生成机理 涉及钼的二氮（N2）络合物。 此外 在该相同系统中肼形成的机理将是 研究了 N2的这些反应涉及一系列酸碱反应， 氧化还原反应 本研究的具体目标有四个。 一是 假设在钼的N2络合物的反应中， 肼在单个钼中心形成，而 氨的形成需要分子间的电子转移 将测试至少两个钼中心之间的距离。 做 这样，钼氮复合物将附着在固体上， 大网状支持，以防止任何分子间 钼中心之间的相互作用。 第二，隔离 N2还原过程中超过（NNH 2）阶段的中间体将 执行。 最初，（NHNH 2）部分将被特异性地 针对性地 第三，钼的N2络合物的范围将 通过使用含S-、O-和N-的配体来延伸。 变化 配位原子的变化可以预期导致氧化还原的变化， 中间体的性质、稳定性和反应途径。 第四，含有多于一种氧化还原活性物质的N2的络合物 金属将被合成，以提高效率， 发生N2还原。 从这些仿生学研究中， 可以提出将N2还原为氨，与此相反，数据 从固氮酶的研究中获得的结果可以进行比较。

Delineating the mechanism of biological nitrogen fixation is a contemporary problem of major importance. As the world's population continues to increase the health and well-being of the people depend upon the availability of sufficient food with protein as an absolutely essential dietary requirement. The long term goals of this research are to elucidate the mechanism of ammonia formation in the biomimetic reduction of N2 and develop catalytic systems for the production of both ammonia and hydrazine. To achieve these goals this research will investigate the mechanism of ammonia formation in a biomimetic system involving dinitrogen (N2) complexes of molybdenum. In addition the mechanism of hydrazine formation in this same system will be studied. These reactions of N2 involve a series of acid-base and redox reactions. The specific aims of this research proposal are four. First, a hypothesis that in the reactions of N2 complexes of molybdenum hydrazine is formed at a single molybdenum center whereas ammonia formation requires intermolecular electron transfer between at least two molybdenum centers will be tested. To do this, molybdenum nitrogen complexes will be attached to solid macroreticular supports in order to prevent any intermolecular interaction between molybdenum centers. Second, isolation of intermediates in the reduction of N2 beyond the (NNH2) stage will be carried out. Initially the (NHNH2) moiety will be specifically targeted. Third, the range of N2 complexes of molybdenum will be extended by using S-, O-, and N-containing ligands. Variations of coordinating atoms can be expected to lead to changes in redox properties, stability of intermediates, and reaction pathways. Fourth, complexes of N2 containing more than one redox active metal will be synthesized in an effort to improve the efficiency of which N2 reduction occurs. From these biomimetic studies a coherent mechanism for the reduction of N2 to ammonia may be proposed, against which data obtained from studies of nitrogenase can be compared.