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的硼酸盐。形成的硼物种在金属硼周围具有笼形和金字塔结构。笼形和结构应变提高了Lewis酸性和催化翻转能力。笼形硼酸酯催化苯甲醛与烯丙基三丁基锡的烯丙化反应，而具有平面结构的苯基硼酸酯B(OPh)3不具有催化活性。对其吡啶络合物进行了核磁共振分析，结果表明其与吡啶形成了较强的相互作用，并在金属周围形成了一个四面体结构。用X-射线单晶衍射法对固态的吡啶配合物进行了表征。B为四面体配位球体，平均键角为O-B-O，114.2(9)°；N-B-O，104.1(9)°。不含吡啶的结构表现为C3对称性。芳环偏离垂直于三个氧原子的平面(约19.2°)，因此，吡啶络合物具有笼状结构的主要性质。铟和硅组成的Lewis酸体系显示出很高的某些反应活性。核磁共振研究清楚地表明，在氯作为桥联原子的作用下，铟与硅发生了相互作用。高的Lewis酸度显示在原位的硅中心。高亲氧性以催化方式加速了醇的直接取代。该催化体系实现了醇在无卤溶剂中的催化取代。该系统被认为是一种理想的、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.