MCn (M = Ga, In, Tl) Coordination Polyhedra in Crystal Structures

The compounds of gallium, indium, and thallium the structures of which contain MC n coordination polyhedra (M = Ga, In, Tl) were subjected to a crystal chemical analysis by the method of intersecting sectors using the Voronoi–Dirichlet polyhedra (VDP). It was determined that the metal atoms in the carbon environment have the coordination numbers 1–7, 9, 10, 12, and 18. The effect of the coordination number, the oxidation state, and the chemical nature of the Ga, In, and Tl atoms on the main characteristics of VDP was studied. It was found that there is a single linear dependence of the solid angles of the VDP faces that correspond to the valence and nonvalence contacts M–C (M = Ga, In, Tl) on the corresponding internuclear distances. The stereo effect of the lone electron pair of the M(I) atoms (M = Ga, In, Tl) was quantitatively estimated, which manifests itself, in particular, in the shift of the M(I) atoms from the barycenters of their VDP (0.03–0.52 Å) and the asymmetry of the coordination sphere. The agostic interactions M···H–C (M = Ga, In, Tl) were analyzed.