Kinetics and Mechanisms of Organometallic Reactions

该奖项将继续支持伊利诺伊大学香槟分校化学系的Theodore L.Brown博士研究过渡金属有机金属化合物在溶液中的反应机理。调查的主线有三条。首先，选择的化合物将通过光化学的方式促进羰基配体的损失，并用低温红外光谱研究反应中间产物。用这种方法研究了双核金属羰基、卡宾铬络合物、氢化锡化和氢化硅化反应。其次，基于Marcus理论的假设，建立了金属有机反应的线性自由能关系式。这部分研究的目的是提高预测由于改变反应条件而导致的反应速率变化的能力。特别是，将研究随着配体的不同而改变电子或空间因素的结果，特别是在原子转移和缔合取代反应中。第三，将分子力学用于评价配体的空间效应。早期的结果表明，用这种方法可以成功地解释配体锥角的影响。金属有机化合物反应机理的研究已进入系统化和概念化阶段。这项工作将为预测某些反应中的反应活性提供指导，这些反应涉及到羰基配体的丢失、原子转移和配体交换。将特别注意评估配体对反应性的影响。这些研究对于了解有机金属化学和涉及有机金属化合物的催化过程具有重要意义，并有助于催化剂的设计。

This award in the Inorganic, Bioinorganic, and Organometallic Program will provide continued support to Dr. Theodore L. Brown of the Chemistry Department, University of Illinois at Urbana-Champaign, for the study of reaction mechanisms of transition metal organometallic compounds in solution. Three main lines of investigation will be pursued. First, the loss of carbonyl ligands from selected compounds will be promoted photochemically, and the reaction intermediates studied using low temperature infrared spectroscopy. Dinuclear metal carbonyls, chromium carbene complexes, hydrostannation and hydrosilation will be studied using this method. Secondly, linear free energy reationships for organometallic reactions will be developed, based on the assumptions of Marcus theory. The purpose of this portion of the reseach is to enhance the ability to predict changes in reaction rates that result from modification of reaction conditions. In particular, the consequences of changes in electronic or steric factors as ligands are varied will be investigated, especially in atom transfer and associative substitution reactions. Thirdly, molecular mechanics will be used to evaluate ligand steric effects. Early results indicate that the influence of ligand cone angles can be successfully interpreted using this approach. %%% Investigation of reaction mechanisms of organometallic compounds is reaching a stage in which the results can begin to be systematized and generalized. This work will provide guidelines for predicting reactivity in some reactions involving loss of a carbonyl ligand, atom transfer, and ligand exchange. Particular attention will be paid to assessing the effect of ligands on reactivity. These studies are important for the fundamental understanding of organometallic chemistry and catalytic processes involving organometallic compounds, and could be helpful for catalyst design.