摘要
在DFT理论水平下研究了全金属芳香性三明治化合物[Sb_3Au_3Sb_3]~(3-)的成键本质。该化合物呈三棱柱结构,具有D_(3h)对称性。分子轨道分析显示该化合物形式上可表述为[Sb_3~(1.5)+Au_3~(3-)Sb_3~(1.5+)]~(3-),此为零级成键图像。上下两个Sb_3环通过分子内电荷转移3个电子给Au_3,使其形成Au_3~(3-);额外三个电荷分配到两个Sb_3环上以补偿电荷转移导致的电子损失。NBO电荷分析则表明Au_3不带电荷,Sb_3带1.5个负电荷,即Sb_3~(1.5-)/Au_3~0/Sb_3~(1.5-),此为有效成键图像。详细的轨道成分和AdNDP分析显示该化合物中的Sb-Au-Sb为3c-2eσ键,这是由分子内价电子复杂的共价重排引起的,接近20个分子轨道场对共价重排有贡献。Sb_3环呈离域3c-3eπ键特征,NICS值为-34.99 ppm,说明其为芳香性化合物。
In a recent communication,an all-metal aromatic sandwich[Sb_3Au_3Sb_3]~(3-) was synthesized and characterized.We report herein a density-functional theory(DFT) study on the chemical bonding of this unique cluster,which makes use of a number of computational tools.In a crude ionic picture the cluster can be formulated as[Sb_3~(1.5+) Au_3~(3-)Sb_3~(1.5+)]~(3-),where an intramolecular transfer of three electrons from Sb to Au results in an Au_3~(3-) layer and the three extra electrons manage to compensate for electron loss of the cyclo-Sb_3 ligands,resulting in Sb_3~0.However,the system is far more covalent than the above picture.Remarkable Sb→Au electron donation and Sb←Au back-donation,which are characteristic of covalent bonding and effectively redistribute electrons from the Sb_3 and Au_3 layers to the interlayer edges.This effect collectively leads to three Sb-Au-Sb three-center two-electron(3c-2e) a bonds as revealed in the AdNDP analyses.NICS analyses confirm the remarkably strong πaromaticity for the all-metal sandwich complex.
引文
[1]Pan,F.X.;Guo,J.C.;Zhai,H.J.;Xu,L.;Sun,Z.M.J.Am.Chem.Soc.,2015,137:10954.
[2]Baird,N.C.J.Am.Chem.Soc.,1972,94:4941.
