Bulky aryl functionalized carbazolyl ligands: amido alternatives to the 2,6-diarylphenyl ligand class?
作者:Natalie D. Coombs、Andreas Stasch、Andrew Cowley、Amber L. Thompson、Simon Aldridge
DOI:10.1039/b716674e
日期:——
Sterically encumbered amido ligands based on a 1,8-diarylcarbazol-9-yl backbone have been investigated as electronically distinct alternatives to the widely-used terphenyl ligand class in the stabilization of low-coordinate metal complexes, and structurally characterized for the first time. While 1,8-diphenylcarbazol-9-yl derivatives are readily available, facile rotation about the Cipso–Cipso bonds leads to structurally characterized main group derivatives e.g. [(1,8-Ph2-3,6-Me2C12H4N)K]2} in which the coordination geometry at the metal centre is augmented by secondary metal–arene interactions. By contrast, the extra bulk inherent in the corresponding 1,8-dimesityl ligand results in essentially perpendicular alignments of the arene and carbazole planes, and a substituent-enforced sterically protected pocket. Comparative structural studies of complexes containing the GaCl2 fragment imply that the 1,8-dimesitylcarbazol-9-yl framework offers greater steric protection at the metal centre than does the corresponding 2,6-dimesitylphenyl ligand.
研究人员对基于 1,8-二苯基咔唑-9-基骨架的立体包被氨基配体进行了研究,将其作为广泛使用的三联苯配体类在稳定低配位金属络合物方面的不同电子替代品,并首次对其进行了结构表征。虽然 1,8-二苯基咔唑-9-基衍生物很容易获得,但通过对 Cipso-Cipso 键的简单旋转,可以得到结构上具有特征的主族衍生物例如[(1,8-Ph2-3,6-Me2C12H4N)K]2},其中金属中心的配位几何形状通过次级金属-烯烃相互作用而增强。相比之下,相应的 1,8-二甲酰配体固有的额外体积导致炔和咔唑平面基本上垂直排列,并形成一个取代基强化的立体保护袋。对含有 GaCl2 片段的配合物进行的结构比较研究表明,1,8-二甲酰基咔唑-9-基框架比相应的 2,6-二甲酰基苯基配体在金属中心提供了更大的立体保护。