Mechanisms of Homogeneous Activation of Hydrocarbons by Transition Metal Complexes

金属化合物被广泛用作促进碳氢化合物结构转化的催化剂，如石油馏分重整生产高辛烷值汽油所需要的催化剂，以及碳-碳键的形成，如利用煤合成有用的有机化合物所必需的催化剂。该项目的目标是提供对这种催化过程的更全面的了解，重点是过渡金属催化碳-碳或碳氢化学键的形成或裂解。将进行过渡金属可溶配合物配位球中烃类反应的机理研究。选择目标体系是为了提供形成或破坏碳氢键和碳氢键的反应的明确例子。可逆烯烃插入金属碳键，分子内γ -C-H活化和分子间C-H活化提供了工作的重点。金属氧化态、立体体积和辅助配体的电子效应、烷基结构、电荷和螯合环大小将作为变量在代表性反应的机制中进行详细研究。所研究的体系包括Pt， Pd， Ti和Zr的配合物，其中含有氘标记的2,2-二甲基-5-戊基配体，通过特定的氘位点交换显示可逆的烯烃插入。用各种氘标记的方平面铱(I)烷基配合物来研究γ - c - h活化。将研究一系列八面体Os（II）和Ir（III）膦和亚磷酸酯烷基氢化物配合物的分子内和分子间C-H活化。通过合成抗环金属化配体来决定烷烃分子间活化的可能性将被研究。在所有情况下，将使用动力学、氘位点标记、动力学同位素效应和底物结构对反应性的影响对机制进行彻底的检查。

Metal compounds are used extensively as catalysts for facilitating structural conversions of hydrocarbons, as required for reforming petroleum distillates to produce high octane gasoline, and for the formation of carbon-carbon bonds, as is necessary in the utilization of coal for the synthesis of useful organic compounds. The goal of this project is to provide a more thorough understanding of such catalytic processes, with a focus on transition metal catalysis of the formation or cleavage of carbon-carbon or carbon-hydrogen chemical bonds. Mechanistic studies of reactions of hydrocarbons in the coordination sphere of soluble complexes of transition metals will be undertaken. The target systems have been chosen to provide well-defined examples of reactions which form or break C-H and C-C bonds. Reversible alkene insertions into metal carbon bonds, intramolecular gamma-C-H activations, and intermolecular C-H activations provide the focus for the work. Metal oxidation state, steric bulk and electronic effects of ancillary ligands, alkyl group structure, charge and chelate ring size will be investigated as variables in a detailed look at the mechanisms of representative reactions. Systems to be studiesd include complexes of Pt, Pd, Ti and Zr containing a deuterium-labeled 2,2-dimethyl-5-pentyl ligand which shows reversible alkene insertion by specific deuterium site exchange. Gamma-C-H activation will be investigated with a variety of deuterium-labeled square-planar iridium(I) alkyl complexes. Intra- and intermolecular C-H activation will be studied in a series of octahedral Os(II) and Ir(III) phosphine and phosphite alkyl hydride complexes. The possibility of dictating a preference for intermolecular activation of alkanes by the synthesis of cyclometallation-resistant ligands will be investigated. In all cases a thorough examination of mechanisms will be made using kinetics, deuterium site labeling, kinetic isotope effects, and the effect of substrate structure on reactivity.