title: Eight-coordinate fluoride in a silicate double-four-ring.
abstract: Fluoride, nature's smallest anion, is capable of covalently coordinating to eight silicon atoms. The setting is a simple and common motif in zeolite chemistry: the box-shaped silicate double-four-ring (D4R). Fluoride seeks its center. It is the strain of box deformation that keeps fluoride in the middle of the box, and freezes what would be a transition state in its absence. Hypervalent bonding ensues. Fluoride's compactness works to its advantage in stabilizing the cage; chloride, bromide, and iodide do not bring about stabilization due to greater steric repulsion with the box frame. The combination of strain and hypervalent bonding, and the way they work in concert to yield this unusual case of multiple hypervalence, has potential for extension to a broader range of solid-state compounds.
authors.affiliation: Inorganic Materials Chemistry, Schuit Institute of Catalysis, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands; M.G.Goesten@TUE.NL rh34@cornell.edu.
authors.forename: Maarten G
authors.initials: MG
authors.lastname: Goesten
authors.affiliation: Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14853-1301; M.G.Goesten@TUE.NL rh34@cornell.edu.
authors.forename: Roald
authors.initials: R
authors.lastname: Hoffmann
authors.affiliation: Department of Theoretical Chemistry, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands.|Institute of Molecules and Materials, Radboud University Nijmegen, 6525 AJ Nijmegen, The Netherlands.
authors.forename: F Matthias
authors.initials: FM
authors.lastname: Bickelhaupt
authors.affiliation: Inorganic Materials Chemistry, Schuit Institute of Catalysis, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands.
authors.forename: Emiel J M
authors.initials: EJ
authors.lastname: Hensen
keywords: chemical bonding; hypervalence; main-group chemistry; zeolite chemistry