MAIN-GROUP FLUORIDE CHEMISTRY

Our research group's contributions to understanding structure and bonding of molecules/ions in which the valence octet is exceeded (often times termed "hypervalent" species) is apparent in our work with "naked fluoride". In collaboration with Prof. Karl O. Christe (Loker Hydrocarbon Institute, University of Southern California, Los Angeles), naked fluoride, in the form of truly anhydrous N(CH₃)₄⁺F^-, has been used to synthesize fluoro- and oxofluoro-anions in which the central atom is frequently in its highest oxidation state and/or at the limits of its coordination, e.g., PF₄^-; (C_2v), PO₂F₂^-; (C_2v), HPO₂F^-; (C_s), XeF₅^-; (D_5h), XeOF₅^-; (C_5v), IOF₆^-; (C_5v), IO₂F₅^2-; (D_5h), TeOF₆^2-; (C_5v), TeF₇^-; (D_5h), TeF₈^2-; (D_4d) and IF₈^-; (D_4d). Several of these anions represent novel VSEPR geometries and, in the case of XeF₅^-, this pentagonal planar anion is, in VSEPR nomenclature, the first example of an AX₅E₂ arrangement which has a pentagonal planar geometry.

We have also extended the highly reactive chemistry of Br(VII) by synthesizing the fourth known Br(VII) species, BrO₃F₂^-, the others being BrO₄^-, BrO₃F and BrF₆⁺.

The BrF₆⁺ cation was also first synthesized by Prof. Schrobilgen by oxidative fluorination of BrF₅ with the strong oxidant cations, KrF⁺ and Kr₂F₃⁺ in liquid BrF₅. The X-ray crystal structures of the cation series XF₆⁺ (X = Cl, Br, I) have been determined as their Sb₂F₁₁^- salts and their solution ¹⁹F and halogen (^35/37Cl, ^79,81Br and ¹²⁷I) NMR spectra have also been studied.