Topological Analysis of the Electron Density Distribution in the Crystal of 8,9,10,12-Tetrafluoro-o-carborane on the Basis of the High-Resolution X-ray Diffraction Data at 120 K

A topological analysis of the electron density distribution ρ(r) in the crystal of 8,9,10,12-tetrafluoro-o-carborane C2B10H8F4 was performed using high-resolution low-temperature (120 K) X-ray diffraction data (14 606 reflections, R = 0.026) and a multipole model for data refinement. Molecules in the crystal (space group Pbcn, Z = 4) occupy special positions on a 2-fold symmetry axis passing through the middle of a C−C bond and the opposite B−B bond of the octahedral cage. Deformation electron density maps as well as maps of the Laplacian of ρ(r) showed that electron density is essentially delocalized over the surface of the cage and locally depleted in its center. All B−B and B−C bonds in the polyhedron are characterized by significant bending, which is evident in shifts of their (3,−1) bond critical points from the straight lines between bonded atoms. Detailed analysis of ρ(r) values and its Laplacian in the bond critical points revealed some unexpected features in the bonding pattern of the structure s...