Cleavage and Formation of Carbon-Carbon Bonds by Transition Metal Complexes

无机、生物无机和有机金属化学项目的长期目标是更深入地了解过渡金属化合物如何影响碳-碳键的裂解和形成。这类反应是化学中最重要的反应之一，并涉及工业过程，如重整汽油以提高辛烷值。该项目的总体策略是分离和模拟有机转化的各个步骤，包括碳-碳键形成或裂解，这些转化受到过渡金属试剂的化学计量和催化作用的影响。重点将放在环丙烯、环丙烯和乙烯基环丙烯配体的化合物上。全氟环丙烯与过渡金属中心的反应将作为C-C键裂解反应的模型，C-C键的氧化加成为金属环丁烯络合物提供了一条途径。3-乙烯基-1-环丙烯转化为1,3-环戊二烯或-5-环戊二烯（氢化物）金属配合物的机理特别有趣，因为涉及顺序的C-C键裂解和C-C键形成步骤。对于一些Rh和ir促进的反应，中间体可以被分离出来，这些中间体的结构表明，打开环丙烯环的机制比简单的环丙烯更复杂，并且不可能涉及金属在C-C键上的“简单”氧化插入。选择性同位素标记前体的反应将用于绘制新的骨架重排的过程，对应于以前未知的有机金属转化，这发生在开环反应期间。同位素标记的前驱体也将用于进一步阐明C-C键形成反应的机理，即Rh（III）和Ir（III）的1,2,3,5- -戊二烯二基和1,5- -戊二烯二基-（1-金属环己基-2,4-二烯）配合物转化为-5- -环戊二烯（氢化物）金属化合物。

The long term objective of this project in the Inorganic, Bioinorganic and Organometallic Chemistry Program is to achieve greater understanding of how transition metal compounds can effect the cleavage and formation of carbon-carbon bonds. Such reactions are among the most important in chemistry and are involved in industrial processes such as reforming gasoline to upgrade the octane number. The overall strategy of the project is to isolate and model the individual steps of organic transformations involving C-C bond forming or cleavage as effected both stoichiometrically and catalytically by transition metal reagents. Emphasis will be placed on compounds with cyclopropenyl, cyclopropene and vinylcylclopropene ligands. Reactions of perfluorocyclopropene with transition metal centers will serve as a model for the C-C bond cleavage reaction, with oxidative addition of the C-C bond providing a route to metallacyclobutene complexes. The mechanism of transformation of 3-vinyl-1-cyclopropenes into 1,3-cyclopentadienes, or into eta-5-cyclopentadienyl(hydrido) metal complexes, are of particular interest since sequential C-C bond cleavage and C-C bond formation steps are involved. For some Rh- and Ir-promoted reactions intermediates can be isolated, and the structures of these intermediates demonstrate that the mechanism for opening the cyclopropene ring is more complicated than for simpler cyclopropenes, and cannot involve a "simple" oxidative insertion of the metal into the C-C bond. Reactions of selectively isotopically labelled precursors will be used to map the course of the novel skeletal rearrangements, corresponding to previously unknown organometallic transformations, which occur during the ring opening reactions. Isotopically labeled precursors will be used also to further elucidate the mechanism of the C-C bond forming reaction whereby 1,2,3,5-eta-pentadienediyl and 1,5-eta-pentadienediyl- (1-metallacyclohexa-2,4-diene) complexes of Rh(III) and Ir(III) undergo conversion to eta-5-cyclopentadienyl(hydrido) metal compounds.