Redox-Control Over Ligand Binding: Consequences for Stoichiometric and Catalytic Reactions

Chad A. Mirkin博士，西北大学化学系，由化学系无机、生物无机和有机金属项目支持，从事过渡金属氧化还原活性配体的研究。这种配体被称为氧化还原可切换半可调配体（RHLs），其设计目的是对它们所结合的过渡金属的空间和电子环境进行电化学控制。这些影响的大小将被量化，静电和感应效应在氧化还原化学引起的结合亲和力变化中的相对重要性将被评估。发生在过渡金属中心的化学转变的电化学控制是最终目标。这些配合物的潜在应用包括催化烯烃加氢、不对称烯烃加氢、硅氢化、氢氰化和甲醇羰基化。人们发现含有金属离子的化合物，如铑，与含有磷、氧和硫原子的分子结合在一起，是特别有用的催化剂，这是因为分子的一部分比另一部分结合得更强。这个项目的目标是合成这种新的分子，被称为氧化还原可切换半可溶配体，其中配体的结合可以通过在配体本身的氧化还原活性取代基上添加或提取电子来控制。因为配体的氧化态可以很容易地用电化学来控制，这可以为催化反应提供一个额外的控制元素，使催化剂的反应性取决于氧化态。预计控制水平的提高将对工业上重要的催化过程产生重要影响。

Dr. Chad A. Mirkin, Department of Chemistry, Northwestern University, is supported by the Inorganic, Bioinorganic, and Organometallic Program of the Chemistry Division to perform studies of redox-active ligands with transition metals. The ligands, known as redox-switchable hemilabile ligands (RHLs), are designed to yield electrochemical control over the steric and electronic environment of the transition metals to which they are bound. The magnitude of these effects will be quantified, and the relative importance of electrostatic and inductive effects in binding affinity changes resulting from the redox chemistry will be assessed. Electrochemical control of chemical transformations that occur at late transition metal centers is the ultimate objective. Potential applications for these complexes include catalytic olefin hydrogenation, asymmetric olefin hydrogenation, hydrosilation, hydrocyanation, and methanol carbonylation. Compounds containing metal ions such as rhodium which are bound to molecules containing phosphorus, oxygen and sulfur atoms have been found to be particularly useful catalysts, and this results from the fact that one part of the molecule binds much more strongly than the other part. The objective of this project is to synthesize new molecules of this sort, known as redox-switchable hemilabile ligands, where the binding of the ligand can be controlled by the addition or abstraction of an electron to or from a redox active substituent on the ligand itself. Because the oxidation state of the ligand can be controlled quite easily using electrochemistry, this could provide an additional element of control to the catalytic reactions, making the catalysts either more or less reactive depending on the oxidation state. The increased level of control is expected to have important implications for industrially important catalytic processes.