SiC_n and SiC_nSi_m Coordination Polyhedra in the Crystal Structures of Silicon-Containing Hydrocarbon Analogs

Crystal-chemical analysis of 1124 silicon compounds with the general formula C_aH_bSi_c (a, b, and c are the stoichiometric coefficients) whose structure contained SiC_n and SiC_nSi_m coordination polyhedra (CPs) has been performed by the intersecting spheres method using Voronoi–Dirichlet polyhedra. In the structure of the compounds, the silicon atoms have coordination numbers (c.n.) of 1–4 and 10. The effects of the coordination number, oxidation state, and chemical nature of the surrounding (C and Si) atoms on the main characteristics of the Voronoi–Dirichlet polyhedra (VDP) of silicon atoms were considered. A single linear dependence of the solid angles of the VDP faces corresponding to the Si–C and Si–Si valence and nonvalence contacts on the corresponding internuclear distances was established. A stereo effect of the lone electron pair of Si(II) atoms in the Si(II)C_n complexes (n = 2 or 10) was revealed, which manifests itself in the displacement of the nuclei of Si(II) atoms from the centers of gravity of their VDP (0.35–0.39 Å) and in the asymmetry of the coordination sphere.