Group 4 Metal Complexes of Boron Heterocycles

Arthur J. Ashe博士，III，密歇根大学化学系，由化学部无机、生物无机和有机金属项目资助，研究涉及第13族和第15族元素的杂芳香族化合物及其过渡金属配合物。以往的研究表明，硼二苯锆配合物可以作为烯烃聚合的均相催化剂。在此结果的基础上，通过类比已知的活性催化剂异茂物，设计了一系列含杂芳配体的金属配合物，以获得高活性和立体特异性的烯烃聚合催化剂。具体地说，将制备具有不同电子和空间要求的悬垂取代基的硼二苯配合物和一系列的桥接硼二苯配合物。这些化合物将利用异芳配体给电子能力的变化进行微调，并开发出更有效的聚合催化剂。最后将制备新的含硼杂环，以扩大可作为配体的杂芳香族化合物的范围。过渡金属配合物促进有机化合物的选择性催化和化学计量转化。金属中心的独特反应性是金属周围电子密度的反映，这种电子密度可以通过调整金属上的基团来控制。一个非常常见的“基团”包含一个碳氢单元环，被称为“芳香”排列。在这个项目中，将制备一系列金属配合物，其中由碳氢和硼组成的“芳香”基团附着在金属上。这将允许仔细调整金属的电子密度，以促进特定的化学和催化行为，并将为理解现有工艺和合理设计新工艺奠定基础。

Dr. Arthur J. Ashe, III, Department of Chemistry, University of Michigan, is supported by the Inorganic, Bioinorganic, and Organometallic Program of the Chemistry Division for the study of heteroaromatic compounds involving group 13 and 15 elements and their transition metal complexes. Previous research has demonstrated that boratabenzene zirconium complexes can serve as homogeneous catalysts for the polymerization of olefins. Building on this result and by analogy to ansametallocenes that are known to be active catalysts, a series of metal complexes containing heteroaromatic ligands will be designed with the goal of obtaining highly active and stereospecific olefin polymerization catalysts. Specifically boratabenzene complexes which bear pendant substituents of varying electronic and steric demand and a series of bridged boratabenzene complexes will be prepared. These compounds will exploit variations in electron donating ability possible with the heteroaromatic ligands to fine tuning and develop more effective polymerization catalysts. Finally new boron containing heterocycles will be prepared in order to extend the range of heteroaromatic compounds available to be used as ligands. Transition metal complexes promote very selective catalytic and stoichiometric transformations of organic compounds. Much of the unique reactivity at the metal center is a reflection of the density of electrons surrounding the metal and this electron density can be controlled by adjusting the groups that are attached to the metal. A very common 'group' contains a ring of carbon-hydrogen units in what is called an 'aromatic' arrangement. In this project a series of metal complexes will be prepared in which an 'aromatic' group composed of carbon-hydrogen and boron species is attached to a metal. This will permit the electron density about the metal to be carefully adjusted in order to promote specific chemical and catalytic behavior and will set the ground work both to understand existing processes and to rationally design new ones.