Syntheses of Square Planar Gallium Complexes and a Proton NMR Correlation Probing Metalloaromaticity
Syntheses of Square Planar Gallium Complexes and a Proton NMR Correlation Probing Metalloaromaticity
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DOI：
10.1021/acs.inorgchem.0c01908
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发表时间：
2020-09-21
影响因子：
4.6
通讯作者：
Berben, Louise A.
中科院分区：
文献类型：
--
作者：
Bass, Thomas M.;Carr, Cody R.;Berben, Louise A.
报道了正方形平面(SP)镓(III)配合物的合成。以吡啶二亚胺(PdI)为配体，合成了(PdI2-)GaH(4)和(PdI2-)GaCl5，并对它们进行了光谱和结构表征。用Na金属还原PDI得到“Na2PDI”，它与原位合成的“GaHCl2”或GaCl3反应生成SP4和SP5。这些和以前报道的SPAl(III)络合物的平面几何结构归因于环电流效应或金属芳香性所产生的能量稳定。通常，含金属环体系中的芳香性很难用实验来表征或确认。一种使用质子核磁共振波谱的实验方法，这里所描述的提供了由与金属芳香性有关的小环电流促进的下场化学位移的估计。近红外光谱分析表明，配体-金属电荷转移带支持芳香性的归属。本文以芳香性为模型，讨论了SP络合物(PdI2-)AlH(1)、(PdI2-)AlCl(2)、(PdI2-)AlI(3)、4和5的电子结构和反应性能。
Syntheses of square planar (SP) coordination complexes of gallium(III) are reported herein. Using the pyridine diimine ligand (PDI), we prepared both (PDI2-)GaH (4) and (PDI2-)GaCl (5), which were spectroscopically and structurally characterized. Reduction of PDI using Na metal afforded "Na2PDI", which reacts with in situ-prepared "GaHCl2" or GaCl3 to afford the SP 4 and 5. 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 (PDI2-)AlH (1), (PDI2-)AlCl (2), (PDI2-)AlI (3), 4, and 5 are all discussed in this report, using aromaticity as a model for their electronic structure and reactivity properties.