Coordination Polyhedra AlCn in Crystal Structures

Abstract

The crystal-chemical analysis of compounds with a structure containing AlC_n coordination polyhedra has been performed using the intersecting sectors method and Voronoi–Dirichlet polyhedra (VDPs). It has been found that the aluminum atoms in the carbon environment have coordination numbers (CNs) 1–7 and 10, with the most typical CN of the aluminum atom being 4. There is a common linear dependence of solid angles of VDP faces corresponding to covalent and noncovalent Al–C contacts on the corresponding internuclear distances. It has been demonstrated that the length of Al–C bonds varies in the range 1.90–2.77 Å, while the VDP volume of the aluminum atom is roughly independent of its CN, being 11.4(7) ų. Criteria for evaluation of the existence of the Al–Al cluster bond in the structure of organoaluminum compounds have been suggested, and the agostic Al⋅⋅⋅H–C interactions have been examined.