Theoretical and experimental (113 K) electron-density study of lithium bis(tetramethylammonium) hexanitrocobaltate(III)

This paper presents an analysis of the crystal structure and the charge density, rho(r), for lithium bis(tetramethylammonium) hexanitrocobaltate(III) determined by the rigid pseudoatom model from accurate X-ray data measured at 113K. This compound has also been investigated by an ab initio Hartree-Fock fully periodic approach. A comparison of the topological properties between the experimentally and theoretically derived density is also given. A notable agreement between experiment and theory is observed in the topological properties of the metal-ligand interaction and a close parallel between the orbital model description and the shape of the Laplacian distribution around the Co atom is outlined. The results confirm the typical 3d-electron distribution of octahedral Co-III complexes in a low-spin state and the presence of four C-H ... O hydrogen bonds in the crystal structure. Important differences between experiment and theory remain for the Laplacian and the parallel curvature (lambda(3)) values at the C-N and N-O bond critical points. The atomic charges derived from the Quantum Theory of Atoms in Molecules are remarkably close to the formal values.