Bass Thomas M, Carr Cody R, Sherbow Tobias J, Fettinger James C, Berben Louise A
Department of Chemistry, University of California, Davis, California 95616, United States.
Inorg Chem. 2020 Sep 21;59(18):13517-13523. doi: 10.1021/acs.inorgchem.0c01908. Epub 2020 Sep 3.
Syntheses of square planar (SP) coordination complexes of gallium(III) are reported herein. Using the pyridine diimine ligand (PDI), we prepared both (PDI)GaH () and (PDI)GaCl (), which were spectroscopically and structurally characterized. Reduction of PDI using Na metal afforded "NaPDI", which reacts with in situ-prepared "GaHCl" or GaCl to afford the SP and . The planar geometry of these and previously reported SP Al(III) complexes is attributed to energetic stabilization derived from a ring-current effect, or metalloaromaticity. Typically, aromaticity in metal-containing ring systems can be difficult to characterize or confirm experimentally. An experimental approach employing proton NMR spectroscopy and described here provided an estimate of a downfield chemical shift promoted by a small ring-current associated with metalloaromaticity. Near infrared spectroscopic analyses display ligand-metal charge transfer bands which support the assignment of aromaticity. The SP complexes (PDI)AlH (), (PDI)AlCl (), (PDI)AlI (), , and are all discussed in this report, using aromaticity as a model for their electronic structure and reactivity properties.
本文报道了镓（III）的平面正方形（SP）配位络合物的合成。使用吡啶二亚胺配体（PDI），我们制备了（PDI）GaH（）和（PDI）GaCl（），并对其进行了光谱和结构表征。用金属钠还原PDI得到“NaPDI”，它与原位制备的“GaHCl”或GaCl反应得到SP 和 。这些以及先前报道的SP铝（III）络合物的平面几何形状归因于由环电流效应或金属芳香性产生的能量稳定化。通常，含金属环系统中的芳香性可能难以通过实验表征或确认。本文介绍的一种采用质子核磁共振光谱的实验方法提供了由与金属芳香性相关的小环电流引起的低场化学位移的估计值。近红外光谱分析显示了配体 - 金属电荷转移带，支持了芳香性的归属。本报告使用芳香性作为其电子结构和反应性质的模型，对SP络合物（PDI）AlH（）、（PDI）AlCl（）、（PDI）AlI（）、 和 进行了讨论。
