INVESTIGATIONS OF BIOMIMETIC NITROGEN FIXATION

描述生物固氮的机制是一个 当代重大问题。作为世界上 人口继续增加人们的健康和福祉 人们依赖于有足够的富含蛋白质的食物 作为一种绝对必要的饮食要求。从长远来看 这项研究的目的是阐明氨的作用机理。 氮气仿生还原的形成与发展 合成氨和合成氨的催化系统 联氨。为了实现这些目标，这项研究将调查 仿生系统中氨的形成机理 涉及钼的氮(N_2)络合物。此外 在同一体系中联氨的形成机理将是 学习。氮气的这些反应涉及一系列的酸碱和 氧化还原反应。 这项研究提案的具体目的有四个。首先，一个 假设在钼的N_2络合物反应中 联氨是在一个钼中心形成的，而 氨的形成需要分子间的电子转移 将对至少两个钼中心之间进行测试。去做 这样，钼氮络合物就会附着在固体上 大网状载体，以防止任何分子间的 钼中心之间的相互作用。第二，隔离 氮气还原超过(NNH2)阶段的中间体将 被执行。最初，(NHNH2)部分将专门 有针对性的。第三，钼的氮络合物的范围将 通过使用S-、O-和N-配体进行扩展。变体 配位原子的变化有望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，含有一个以上氧化还原活性的氮的络合物 将合成金属，以努力提高金属的效率 氮气发生了哪一种还原。 从这些仿生研究中得出了一种连贯的机制 可以建议将氮气还原为氨，这与数据 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.