Organoboron Derivatives of Group 4 Metals

阿瑟·J·阿什博士，III，密歇根大学化学系，得到化学部无机、生物无机和有机金属计划的支持，该计划旨在研究含有第13和15族元素的杂芳烃化合物，将其用作配体以形成锆络合物，并将这些络合物开发为烯烃聚合催化剂。以往的研究表明，硼苯锆络合物可以作为烯烃聚合的均相催化剂。在这一结果的基础上，通过类比已知的活性催化剂反式茂金属，将设计一系列含有杂芳烃配体的金属络合物，以获得高活性和立体专一性的烯烃聚合催化剂。具体地说，将合成新的氧硼内酯、硫硼内酯和氮硼内酯。这些化合物与通过硼或碳-(2)桥联的硼苯将被用作配体，形成第四族金属络合物，将被评估为聚合催化剂。此外，还将研究氨基硼烷桥联的锆烯转化为高活性和立体选择性的Ziegler-Natta催化剂。过渡金属络合物促进有机化合物的非常选择性的催化和化学计量转化。金属中心的许多独特的反应性反映了金属周围的电子密度，这种电子密度可以通过调节连接到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，这种环被称为‘芳香族’排列。在这个项目中，将制备一系列金属络合物，其中一个由碳、氢和硼物种组成的‘芳香’基团连接到金属上。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，并将为了解现有工艺和合理设计新催化剂奠定基础。

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, their use as ligands to form zirconium complexes, and the development of these complexes as olefin polymerization catalysts. 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, new oxaborolides, thiaborolides and azaborolides will be synthesized. These compounds along with boratabenzenes, which are bridged through boron or carbon-(2), will be used as ligands to form Group 4 metal complexes, which will be evaluated as polymerization catalysts. Additionally, the conversion of aminoboranediyl bridged zirconocenes to highly active and stereoselective Ziegler-Natta catalysts will be studied.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 catalysts.