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。所形成的硼种在硼金属周围具有笼形和锥体结构。笼形和结构应变提高了Lewis酸度和催化转化率。笼形硼酸盐催化苯甲醛与烯丙基三丁基锡的烯丙基化反应，而具有平面结构的苯硼酸B(OPh)_3没有表现出催化活性。硼酸盐与吡啶配合物的核磁共振分析表明，硼酸盐与吡啶的相互作用强，并在金属周围呈四面体结构。用x射线晶体学对固态吡啶配合物进行了表征。硼具有一个四面体配位球，键角平均值为：O-B-O为114.2(9)°，N-B-O为104.1(9)°。不含吡啶的结构表现为C_3对称。芳香环偏离三个氧的垂直平面（约19.2°），因此，吡啶配合物具有笼状结构引起的键性。铟硅复合路易斯酸体系的某些反应具有很高的活性。核磁共振研究清楚地显示了以Cl为桥原子介导的铟与硅的相互作用。高路易斯酸度表现在原位硅中心。高亲氧性加速了醇的催化直接取代。该催化体系实现了醇类在无卤溶剂中的催化取代。该系统被认为是一种理想的、实用的工业化学工艺。

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.