Sterically and Electronically Designed Metal Species for Reactions

三（2-羟基苯基）甲烷与硼烷反应生成结构应变硼酸盐。所形成的硼物质具有笼形和围绕硼金属的金字塔结构。笼状结构和结构应变增强了刘易斯酸性和催化转化率。笼状硼酸酯催化苯甲醛与烯丙基三丁基锡的烯丙基化反应，而具有平面结构的硼酸苯酯B（OPh）3没有催化活性。通过核磁共振分析了其吡啶配合物，结果表明硼酸盐与吡啶之间有很强的相互作用，并在金属周围形成了四面体结构。用X射线晶体学方法对吡啶配合物进行了表征。硼为四面体配位球，平均键角为O-B-O，114.2（9）°和N-B-O，104.1（9）°。不含吡啶的结构为C_3对称。吡啶配合物的芳香环偏离了三个氧原子的垂直面（约19.2 °），具有笼形结构引起的手性，铟硅刘易斯酸体系对某些反应表现出很高的活性。核磁共振研究清楚地表明了铟与硅之间的相互作用是由Cl作为桥原子介导的。高的刘易斯酸性原位显示在硅中心上。高的亲氧性以催化方式促进醇的直接取代。该催化剂体系在无卤素溶剂中实现了醇的催化取代。认为该体系是一种理想而实用的工业化学过程。

A structurally strained borate was generated in the reaction of tris(2-hydoxyphenyl)methane with borane. The formed boron species has a cage-shape and a pyramidal structure around the boron metal. The cage-shape and structural strain enhance the Lewis acidity and catalytic turn-overs. The cage-shaped borate catalyzed the allylation of benzaldehyde with allyltributyltin, while phenyl borate B(OPh)_3,which has a planar structure, did not show catalytic acitivity. Its pyridine complex was analyzed by NMR which shows strong interaction of the borate with pyridine and a tetrahedral structure around the metal. The pyridine complex in solid state was characterized by X-ray crystallography. Boron has a tetrahedral coordination sphere with the average of bond angles (O-B-O,114.2(9)° and N-B-O,104.1(9)°). The structure without pyridine shows C_3 symmetry. The aromatic rings deviate from a perpendicular plane to that of three oxygens (ca.19.2°) and thus, the pyridine-complex has chiality that is caused by the cage-shape.The combined Lewis acid system using indium and silicon showed very high activity of some reactions. An NMR study clearly showed the interaction of the indium with silicon mediated by Cl as a bridged atom. The high Lewis acidity showed up on the silicon center in situ. The high oxophilicity accelerated the direct subsitution of alcohols in a catalytic manner. The catalyst system accomplished the catalytic substitution of alcohols in a halogen-free solvent. The system is considered to be an ideal and practical process for industrial chemisty.