Organometallic Radical Chemistry; Cage Effects and Reactivity in Aqueous Solution

在这个由无机、生物无机和有机金属化学项目支持的项目中，俄勒冈大学化学系的David R. Tyler博士将继续他对有机金属自由基反应性的研究。该项目的第一部分涉及使用时间分辨泵浦/探针光谱和“慢”动力学方法来测量一系列光化学和热生成的有机金属自由基的笼形效应，包括Mo取代环戊二烯基化合物、钛茂烯和钴酰肟。笼效应是指溶液中自由基对结合的概率大于气相的现象。在化学和生物化学的各个领域，笼效应是解释溶液中化学反应的动力学观察和基本反应现象所必需的。实验将探讨自由基的大小、形状和质量对笼形效应的影响。“微观惯性”和溶剂“微粘度”的概念将被探讨，因为它们与笼形效应有关。具有长链的自由基也将被研究，因为它们与聚合物和生物化学直接相关。本研究的目的是获得对笼效应的预测性理解。本课题第二部分将重点研究水溶性有机金属自由基在水溶液中的反应性。将研究光化学和电化学生成的17电子取代反应，以及氧化诱导的迁移插入反应。这些反应的动力学和活化参数将通过红外光谱和计时测光实验来确定，目的是确定反应机理。有机金属自由基催化的电子转移链反应也将被研究，重点是确定水溶液和非水溶液之间自由基反应性的差异。本文还将合成几种新的水溶性膦配体，并利用Rh配合物进行双相氢甲酰化和加氢催化实验。这个项目将提供有用的和根本重要的信息，在溶液中涉及自由基的反应的性质，具有奇数电子的活性化学化合物。自由基反应在化学和生物化学中普遍存在，包括聚合反应（塑料和纤维）和维持生命的酶反应。水溶性有机金属催化剂的研究结果将具有基础性和实用性。工业生产的大多数化学品都涉及催化作用，许多过程使用挥发性和有毒的有机溶剂。开发以水为溶剂的催化剂有令人信服的环境原因。

In this project, which is supported by the Inorganic, Bioinorganic, and Organometallic Chemistry Program, Dr. David R. Tyler of the Department of Chemistry, University of Oregon, will continue his studies on organometallic radical reactivity. The first part of the project involves using time-resolved pump/probe spectroscopy and `slow` kinetic methods to measure the cage effect for a series of photochemically and thermally generated organometallic radicals, including substituted cyclopentadienyl compounds of Mo, titanocenes, and cobaloximes. The cage effect refers to the phenomenon that the probability of combination of a radical pair is greater in solution than in the gas phase. Cage effects are necessary to explain kinetic observations and fundamental reaction phenomena for chemical reactivity in solution in all areas of chemistry and biochemistry. Experiments will probe the effect of radical size, shape, and mass on the cage effect. The concepts of `microscopic inertia` and solvent `microviscosity` will be probed as they relate to the cage effect. Radicals with long chains will also be examined as these are directly relevant to polymer and bio-chemistry. The goal of this research is to acquire a predictive understanding of the cage effect. The second part of this project will focus on studies of the reactivity of water soluble organometallic radical species in aqueous solution. Substitution reactions of photochemically and electrochemically generated 17-electron species will be studied, as will oxidatively-induced migratory insertion reactions. The kinetics and activation parameters of these reactions will be determined by infrared spectroscopy and chronocoulometry experiments, with the goal of determining reaction mechanisms. Electron-transfer-chain reactions catalyzed by organometallic radicals will also be studied with an emphasis on determining the differences in radical reactivity between aqueous and nonaqueous solutions. Several new water soluble phosphine ligands will also be synthesized and tested in biphasic hydroformylation and hydrogenation catalysis experiments using Rh complexes. This project will provide useful and fundamentally important information on the nature of reactions in solution that involve radicals, reactive chemical compounds with an odd number of electrons. Radical reactions are ubiquitous in chemistry and biochemistry and include polymerization reactions (plastics and fibers) and life sustaining enzyme reactions. Results of the work with water soluble organometallic catalysts will be fundamental and practical. Most chemicals produced in industry involve catalysis and many processes use volatile and toxic organic solvents. There are compelling environmental reasons to develop catalysts that can use water as a solvent.