Center for Nanoscale Science and Engineering, North Dakota State University, 1805 NDSU Research Park Drive, Fargo, North Dakota 58102, USA.
Inorg Chem. 2011 May 2;50(9):4047-53. doi: 10.1021/ic102535n. Epub 2011 Apr 4.
The addition of halide anions (X' = Cl(-), Br(-), or I(-)) to perhalocyclohexasilane Si(6)X(12) (X = Cl or Br) led to the formation of complexes comprising Si(6)X(12)X'(2) dianions. An upfield shift in the (29)Si NMR spectra was noted upon coordination, and structural determination by X-ray crystallography showed that the dianions adopt an "inverse sandwich" structure where the six cyclic silicon atoms form a planar hexagon with the two halide anions X' located on the 6-fold axis equally disposed above and below the plane of the Si(6) ring. Additionally, these apical X' atoms are within the van der Waals bonding distance to the silicon ring atoms, indicating a strong interaction between X' and silicon atoms. These results detail crystallographic variations within the halogen series providing further insight into the nature of the Lewis acid sites above and below the Si(6)X(12) ring, where interactions with hard Lewis bases such as halide anions are observed. Interestingly, the stereochemistry of the silicon atoms in Si(6)X(12)X'(2) is not affected much by the size or electronegativity of the halogen atoms.
卤素阴离子（X'=Cl(-)、Br(-)或 I(-)）的加入导致了全卤代环己六硅烷 Si(6)X(12)（X=Cl 或 Br）的形成，形成了包含Si(6)X(12)X'(2)二阴离子的配合物。配位后，(29)Si NMR 光谱发生了向上场位移，通过 X 射线晶体学结构测定表明，二阴离子采用“反夹心”结构，其中六个环状硅原子形成一个平面六边形，两个卤素阴离子 X'位于六重轴上，均匀地位于 Si(6)环平面的上方和下方。此外，这些顶端 X'原子处于范德华键合距离内，与硅环原子相连，表明 X'与硅原子之间存在强烈的相互作用。这些结果详细描述了卤族元素系列中的晶体变化，进一步深入了解 Si(6)X(12)环上方和下方路易斯酸位的性质，观察到与硬路易斯碱（如卤素阴离子）的相互作用。有趣的是，Si(6)X(12)X'(2)中硅原子的立体化学受卤素原子的大小和电负性影响不大。
