Charge density of difluorides from synchrotron diffraction data and investigation of bonding in low valent binary fluorides

Abstract

The experimental charge density analysis of two isostructural transition metal difluorides, CoF2 and NiF2 has been performed using single crystal synchrotron X-ray diffraction data. The multipole and MEM models of electron density and the thermal vibration parameters suggest that the difluoride of nickel is a hard molecule with more shared shell interaction nature than the difluoride of cobalt. In the course of study, a comparative study on fluorine bonding in low valent binary fluorides with metal cations of oxidation states, ranging from +1 to +3 have been accomplished and thoroughly analysed. The explored topological features derived from the Bader's theory of Atoms In Molecules (AIM) approach reveals the existence of ionic nature of bonding at +1 valence state of metal, as viewed in LiF and NaF and as the oxidation on metals ascends, intermediate interaction with increase in covalent nature is evidenced.