Making and Breaking Carbon-Carbon Bonds at Transition Metal Centers

达特茅斯学院化学系Russell P.Hughes博士得到化学系无机、生物无机和有机金属项目的支持，以确定过渡金属如何形成和破坏碳-碳键。为了研究金属介导的碳-碳裂解和形成的范围，将对金属中心可逆插入环丙烯基环的碳-碳键进行详细的机理研究。由于金属介导的碳-碳形成反应的产物往往依赖于金属络合物的构象性质，因此，含两个环戊二烯配体的金属络合物的构象性质将被连接到环戊二烯环上来控制。这将迫使来自两个非手性环戊二烯配体的不对称和不对称配合物自组装。利用环丙烯和环戊二烯环上相邻叔丁基团所赋予的空间位阻，可以生成新的金属-环戊二烯基段的价异构体和新的含有金属-碳和金属-杂原子多键的过渡金属络合物。过渡金属络合物促进有机化合物非常选择性的催化和化学计量转化。由于这些反应中的许多都涉及通常的惰性键的激活，因此了解金属中心如何在碳原子之间建立和断开键是相当有兴趣的。本研究旨在对这一过程有一个基本的理解。将获得的详细知识将允许增加金属催化剂的使用和扩展，并将允许对催化剂进行微调，以便精确地控制化学反应。

Dr. Russell P. Hughes, Department of Chemistry, Dartmouth College, is supported by the Inorganic, Bioinorganic, and Organometallic Program of the Chemistry Division to determine how transition metals make and break carbon-carbon bonds. To investigate the scope of metal-mediated carbon-carbon cleavage and formation, detailed mechanistic studies will be carried out for the reversible insertion of metal centers into the carbon-carbon bonds of cyclopropenyl rings. As the product of metal-mediated carbon-carbon forming reactions is often dependent on the conformational properties of the metal complex, `sticky` fluorinated substituents will be attached to cyclopentadienyl rings to control conformational properties of metal complexes containing two cyclopentadienyl ligands. This will force the self-assembly of dissymmetric and asymmetric complexes from two achiral cyclopentadienyl ligands. New valence isomers of the metal-cyclopentadienyl fragment and new transition metal complexes containing metal-carbon and metal-heteroatom multiple bonds will be produced through harnessing the steric strain imparted by adjacent tertiary butyl groups on cyclopropenyl and cyclopentadienyl rings to force skeletal rearrangements. Transition metal complexes promote very selective catalytic and stoichiometric transformations of organic compounds. Since many of these reactions involve the activation of normally inert bonds, it is of considerable interest to understand how metal centers make and break bonds between carbon atoms. This study aims toward a fundamental understanding of such processes. The detailed knowledge that will be obtained will permit an increased usage and expansion of metal catalysts and will permit the catalysts to be fine tuned in order to precisely control chemical reactions.