Cage-Shaped Borate Esters with Tris(2-oxyphenyl)methane or -silane System Frameworks Bearing Multiple Tuning Factors: Geometric and Substituent Effects on Their Lewis Acid Properties
作者:Makoto Yasuda、Hideto Nakajima、Ryosuke Takeda、Sachiko Yoshioka、Satoshi Yamasaki、Kouji Chiba、Akio Baba
DOI:10.1002/chem.201002789
日期:2011.3.28
Boron complexes that contain new tridentate ligands, tris(o‐oxyaryl)methanes and ‐silanes, were prepared. These complexes had a cage‐shaped structure around a boron center and showed higher Lewis acidity and catalytic activity than open‐shaped boron compounds. The cage‐shaped ligands determined the properties of the borates by altering the geometry and were consistently bound to the metal center by
制备了含有新的三齿配体,三(邻-氧芳基)甲烷和-硅烷的硼配合物。这些络合物在硼中心周围具有笼状结构,并且比开放型硼化合物具有更高的路易斯酸度和催化活性。笼状配体通过改变几何形状决定了硼酸盐的性质,并通过螯合作用始终与金属中心结合。合成的化合物是L⋅B(OC 6 H 4)3 CH,L⋅B(OC 6 H 4)3 SiMe及其衍生物(L = THF或吡啶作为外部配体)。理论计算表明,笼形硼酸盐具有较大的二面角(C ipso-O-B-O)与开放形状的硼酸盐相比。由于二面角的几何作用,意味着与开口形相比,笼形硼酸盐具有更高的路易斯酸度。在笼形框架的芳基部分引入吸电子基团增加了路易斯酸度。用桥头硅代替桥头C会降低硼配合物的路易斯酸度,因为大的硅原子会降低C ipso -B-O的二面角。对氟取代的化合物B(OC 6 H 3 F)3 CH和邻苯基取代的化合物B(OC 6 H 3 Ph)3的配体交换率CH小于未取代的硼酸盐B(OC