Organometallic Radical Chemistry; Cage Effects and Reactivity in Aqueous Solution

在这个由无机化学、生物无机化学和金属有机化学项目支持的项目中，俄勒冈大学化学系的戴维·R·泰勒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/探测光谱和“慢”动力学方法来测量一系列以光化学和热产生的有机金属自由基的笼子效应，包括取代的环戊二烯化合物钼、二茂钛和钴肟。笼效应是指自由基对在溶液中结合的几率大于在气相中结合的几率的现象。笼子效应是解释化学和生物化学所有领域中溶液中化学反应的动力学观察和基本反应现象所必需的。实验将探索径向尺寸、形状和质量对笼子效应的影响。我们将探讨“微观惯性”和“微粘度”的概念，因为它们与笼子效应有关。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。本研究的目的是对笼子效应有一个预测性的了解。本项目的第二部分将重点研究水溶性有机金属自由基物种在水溶液中的反应性。将研究光化学和电化学产生的17电子物种的取代反应，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库仑实验来确定，目的是确定反应机理。还将研究有机金属自由基催化的电子转移链式反应，重点是确定水溶液和非水溶液中自由基反应活性的差异。还将合成几种新的水溶性膦配体，并用Rh络合物进行两相氢甲酰化和氢化催化实验。这个项目将提供有关溶液中反应性质的有用和基本重要的信息，这些反应涉及自由基，即具有奇数个电子的活性化合物。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。工业中生产的大多数化学品涉及催化，许多过程使用挥发性和有毒的有机溶剂。有令人信服的环境理由来开发可以使用水作为溶剂的催化剂。

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.