NSF Young Investigator: Transition Metal Complexes with Optically Active Pyrazolyl Ligands

明尼苏达大学的托尔曼教授将在美国国家科学基金会无机、生物无机和有机金属化学项目青年研究员奖的帮助下研究过渡金属配位化合物。他的研究项目集中在两个主题上，这两个主题通过使用吡唑基配体联系在一起。其中一个项目将使用这些配体制备铜化合物，这些铜化合物可以与氧氮化合物（如NO）相互作用；目的是使用简单的配位化学来提高我们对铜在酶促反硝化中的作用的理解。另一个项目将使用这些配体的手性版本在手性三重环境中结合金属离子；预计这种金属中心将能够以与更常见的手性2重金属中心明显不同的方式介导立体选择反应。分子中金属离子的存在可以赋予这些分子不寻常的性质。在某些细菌酶中发现了一个现实世界的例子，其中铜离子导致亚硝酸盐转化为氮气等气体；这个特殊的反应是全球氮循环的主要组成部分。目前对铜氮化合物的基本化学性质了解甚少。有了这笔拨款，将制备含有铜和各种含氮成分的简单分子，并研究它们的反应。金属离子异常行为的另一个例子是含有金属离子的分子具有手性（即手性）的能力，从而催化重要的反应，只产生多种可能产物中的一种。这笔拨款将使研究这样的系统，手性是基于金属离子的三重对称，而不是更不寻常的双重对称。预计这种对称的变化将导致催化活性的实质性差异，潜在的工业效益。

Proposal: 9357171 PI: Tolman Professor Tolman, of the University of Minnesota, will investigate the transition metal coordination compounds with the assistance of an NSF Young Investigator Award from the Inorganic, Bioinorganic, and Organometallic Chemistry Program. His research program is focussed on two subjects, which are linked by their use of pyrazolyl ligands. One of the projects will use these ligands to prepare copper compounds that can interact with oxonitrogen compounds such as NO; the objective is to use simple coordination chemistry to enhance our understanding of the role of copper in enzymatic denitrification. The other project will use chiral versions of these ligands to bind metal ions in a chiral 3-fold environment; it is anticipated that such metal centers will be able to mediate stereoselective reactions in ways that differ significantly from the more usual chiral 2-fold metal centers. %%% The presence of metal ions in molecules can endow these molecules with unusual properties. A real-world example is found in certain bacterial enzymes, where copper ions lead to the conversion of nitrite to gases such as N2; this particular reaction is a major component of the global nitrogen cycle. The underlying chemistry of copper-nitrogen compounds is presently very poorly understood. With this grant, simple molecules containing copper and various nitrogenous components will be prepared, and their reactions will be studied. Another example of unusual metal ion behavior is the ability of molecules containing metal ions to have the property of chirality (i.e., handedness), and thereby to catalyze important reactions to give only one of a variety of possible products. This grant will enable studies of such systems where the chirality is based on a three-fold symmetry about the metal ion, rather than the more unusual two-fold symmetry. It is expected that this change of symmetry will lead to substantial differences in catalytic activity, poten tially of industrial benefit.