Thermochemical and Reactivity Studies of Basic Transition Metal Complexes

许多过渡金属配合物表现为碱，它们与质子酸反应生成金属氢化物就说明了这一点。有证据表明，这种碱度也影响这些配合物的其他类型的反应性。为了了解这些反应性，各种过渡金属配合物的碱度将通过用三酸量热法测量它们的质子化热来确定。本文将系统地研究一系列具有多种配体的单核配合物，以建立金属碱度与其所附配体性质之间的定量关系。单齿配体的电子和空间效应将被检查，并将研究由螯合配体引起的反应物和/或产物结构扭曲引起的碱度变化。此外，影响双核和簇状配合物碱度的因素，其中质子化发生在金属-金属键上，将被研究。为了了解金属配合物的碱度如何影响其他类型的配合物反应活性，将测定各种氧化加成反应的速率并将其与焓值相关联；这样的线性自由能相关性应该是非常有用的指南，以了解广泛的过渡金属配合物的反应性。在化学部无机、生物无机和有机金属项目中，爱荷华州立大学的Robert J. Angelici博士将继续进行各种过渡金属配合物的热化学和反应性研究。一组有限的热化学数据可能允许对大范围的化学反应进行准确的预测，这种预测能力可能在某些催化剂的设计中被证明是非常有用的。

Many transition metal complexes behave as bases as illustrated by their reactions with protonic acids to give metal hydrides. There is evidence that this basicity also influences other types of reactivity of these complexes. To understand these reactivities, basicities of a variety of transition metal complexes will be determined by measuring their heats of protonation calorimetrically with triflic acid. Series of mononuclear complexes with a variety of ligands will be studied systematically in order to establish quantitative relationships between the metal basicity and the natures of the ligands attached to it. Electronic and steric effects of monodentate ligands will be examined, and basicity changes caused by distortions of reactant and/or product structures induced by chelating ligands will be studied. Also, factors which affect basicities of dinuclear and cluster complexes, where protonation occurs on a metal-metal bond, will be investigated. In order to understand how metal complex basicities influence other types of complex reactivity, rates of a variety of oxidative-addition reactions will be determined and correlated with the enthalpy values; such linear free energy correlations should be extremely useful guides to understanding a broad range of transition metal complex reactivity. %%% In this project in the Inorganic, Bioinorganic, and Organometallic Program of the Chemistry Division, Dr. Robert J. Angelici of Iowa State University will continue thermochemical and reactivity studies of a variety of transition metal complexes. It is possible that a limited set of thermochemical data may allow accurate predictions of a large range of chemical reactivities, a predictive capability that could prove very useful in the design of certain catalysts.