平面五配位硅、锗XBe_(5)H_(6)(X=Si,Ge)团簇

Planar Pentacoordinate Silicon and Germanium in XBe_(5)H_(6)(X=Si,Ge) Clusters

采用密度泛函理论PBE0方法,在aug-cc-pVTZ水平上理论预测了含平面五配位硅和锗原子的XBe_(5)H_(6)(X=Si,Ge)团簇.势能面系统搜索及高精度量化计算表明,它们均为全局极小结构.XBe_(5)H_(6)(X=Si,Ge)团簇整体呈完美的扇形结构:Si/Ge原子被5个金属Be原子配位;4个H原子以桥基方式与Be原子相键连,剩余的2个H原子以端基方式与两端的Be原子成键.化学键分析表明,XBe_(5)H_(6)(X=Si,Ge)团簇中XBe_(5)单元具有完全离域的1个π及3个σ键,外围铍氢间形成4个Be—H—Be三中心二电子(3c-2e)键及2个定域的Be—H键.XBe_(5)单元上离域的2π及6σ电子赋予体系π和σ双重芳香性,并使Si/Ge原子满足八隅律(或八电子规则).能量分解化学价自然轨道分析揭示,Si/Ge和Be_(5)H_(6)之间主要为电子共享键.

Computational design of ternary XBe_(5)H_(6)(X=Si,Ge)clusters was reported,which were global-minimum structures on the potential energy surfaces,featuring planar pentacoordinate silicon/germanium(ppSi/Ge).XBe_(5)H_(6)(X=Si,Ge)clusters have the perfect fan-shaped structures:Si/Ge atoms are coordinated by five Be atoms;four H atoms are bonded to Be atoms in bridge mode,and the remaining two H atoms are bonded to Be atoms at both ends.Chemical bonding analyses reveal that the ppSi/Ge core is governed by delocalized 2π/6σbonding,that is,doubleπ/σaromaticity,which also makes the Si/Ge atom conform to the octet rule.Additional twelve electrons are contributed to peripheral Be—H—Be and Be—Hσbonding.Energy decomposition analysis-Natural orbital for chemical valence(EDA-NOCV)analyses indicate that there is mainly electron-sharing bonding between the Si/Ge and Be5H6 ligands.