Covalent versus ionic bonding in alkalimetal fluoride oligomers.

摘要: The most polar bond in chemistry is that between a fluorine and an alkalimetal atom. Inspired by our recent finding other bonds (CM HM) have important covalent contributions (i.e., stabilization due to overlap), we herein address the question if covalency also essential FM bond. Thus, theoretically studied fluoride monomers, FM, (distorted) cubic tetramers, (FM)4, with M = Li, Na, K, Rb, using density functional theory at BP86/TZ2P level. Our objective determine how structure thermochemistry (e.g., lengths strengths, oligomerization energies, etc.) of fluorides depend on metal atom, understand emerging trends terms quantitative Kohn–Sham molecular orbital theory. analyses confirm extreme polarity (dipole moment, Voronoi deformation Hirshfeld atomic charges), they reveal overlap-derived (ca. −6, −2 kcal/mol) contributes only little strength (−136, −112, −114 trend therein along K. According this criteria, not strongly polar, but has truly ionic bonding mechanism. Interestingly, reduced tetramerization. For lithium sodium F4 tetrahedron larger than surrounds M4 cluster FF ≫ MM). But potassium rubidium smaller inside < © 2006 Wiley Periodicals, Inc. J Comput Chem 28: 238–250, 2007