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

这个项目在无机、生物无机和金属有机化学计划中的长期目标是更好地了解过渡金属化合物如何影响碳-碳键的断裂和形成。这类反应是化学中最重要的反应之一，涉及工业过程，如重整汽油以提高辛烷值。该项目的总体战略是分离和模拟涉及C-C键形成或裂解的有机转化的各个步骤，这些步骤既有化学计量作用，也有过渡金属试剂的催化作用。重点将放在具有环丙烯、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键断裂反应的模型，C-C键的氧化加成为金属环丁烯配合物提供了一条途径。3-乙烯-1-环丙烯转化为1，3-环戊二烯或ETA-5-环戊二烯基(氢化)金属络合物的反应机理特别有趣，因为涉及到顺序的C-C键断裂和C-C键形成步骤。对于一些Rh和Ir促进的反应，可以分离出中间体，这些中间体的结构表明，开环丙烯的机理比更简单的环丙烯更复杂，不涉及金属在C-C键上的“简单”氧化插入。选择性同位素标记的前体的反应将被用来绘制新的骨架重排的过程，对应于在开环反应中发生的先前未知的有机金属转变。同位素标记的前体也将被用来进一步阐明1，2，3，5-ETA-五二烯二基和1，5-ETA-五二烯-(1-金属环己-2，4-二烯)Rh(III)和Ir(III)的C-C键形成反应的机理。

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.