Max Planck Institute for Chemical Physics of Solids, Noethnitzer Str. 40, 01187 Dresden, Germany.
Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Genova, I-16146 Genova, Italy.
Dalton Trans. 2023 Jun 20;52(24):8222-8236. doi: 10.1039/d3dt00621b.
Application of chemical bonding analysis in position-space techniques based on combined topological analysis of the electron density and electron-localizability indicator distributions has recently led to the formulation of a polarity-extended 8 - rule for consistent inclusion of quantum chemically obtained polar-covalent bonding data into the classical 8 - scheme for main-group compounds. Previous application of this scheme to semiconducting main-group compounds of the cubic MgAgAs type of structure with 8 valence electrons per formula unit (8 ve per f.u.) has shown a covalent bonding tendency preferring one zinc blende type partial structure over the other one, which seems to corroborate the classical Lewis picture of maximally four covalent bonds per main-group element. In contrast to the MgAgAs type, the orthorhombic TiNiSi type of structure displays a much higher geometrical flexibility to incorporate different kinds of metal atoms. The analysis of polar-covalent bonding in semiconducting 8 ve per f.u. containing main-group compounds ' of this structure type reveals a transition to non-Lewis type bonding scenarios of species with up to ten polar-covalently bonded metal atoms. This kind of situation is consistently included into the extended 8 - type bonding scheme. A systematic increase of partially covalent bonding from chalcogenides to the tetrelides is found, summing up to as much as 2 covalent bonds and -', and correspondingly remaining 4 lone pair type electrons on species . The familiar notion of this structure type consisting of a '[NiSi]'-type framework with 'Ti'-type atoms filling the voids cannot be supported for the compounds investigated.
基于电子密度和电子定域化指标分布的联合拓扑分析，化学键分析在基于位形空间的技术中的应用最近导致了极性扩展的 8 规则的制定，用于将量子化学获得的极性共价键数据一致地纳入主族化合物的经典 8 规则中。该方案先前应用于具有每个分子式单位 8 个价电子的立方 MgAgAs 型结构的半导体主族化合物，表现出一种共价键倾向，优先选择一种闪锌矿型部分结构而不是另一种结构，这似乎证实了主族元素每个最多有四个共价键的经典 Lewis 图像。与 MgAgAs 型相比，正交 TiNiSi 型结构显示出更高的几何灵活性，可以容纳不同种类的金属原子。对这种结构类型的含有 8 个价电子的半导体主族化合物中的极性共价键的分析揭示了从具有多达十个极性共价键合金属原子的物种向非 Lewis 型键合方案的转变。这种情况始终被纳入扩展的 8 规则中。从硫属化物到四卤化物，部分共价键合呈系统增加，总计高达 2 个共价键和 -'，相应地，物种上剩余 4 个孤对电子类型。对于所研究的化合物，不能支持该结构类型由具有“Ti”型原子填充空隙的“[NiSi]”-型框架组成的常见概念。
