Thermochemical and Reactivity Studies of Basic Transition Metal Complexes

许多过渡金属络合物作为碱，它们与质子酸反应生成金属氢化物。有证据表明，这种碱性也影响这些络合物的其他类型的反应性。为了了解这些反应性，各种过渡金属络合物的碱性将通过用三氟酸量热法测量它们的质子化热来确定。为了建立金属碱度与配体性质之间的定量关系，我们将对一系列具有不同配体的单核配合物进行系统的研究。将考察单齿配体的电子和空间效应，并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，还将研究影响双核和簇合物碱性的因素，其中质子化发生在金属-金属键上。为了了解金属络合物的碱性如何影响其他类型的络合反应性，将测定各种氧化加成反应的速率并与热值相关联；这种线性自由能关联对于理解广泛的过渡金属络合物反应性应该是非常有用的指导。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博士将继续对各种过渡金属络合物进行热化学和反应性研究。有限的一组热化学数据可能能够准确预测大范围的化学反应，这一预测能力可能被证明在某些催化剂的设计中非常有用。

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.