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-; (C2v), PO2F2-; (C2v), HPO2F-; (Cs), XeF5-; (D5h), XeOF5-; (C5v), IOF6-; (C5v), IO2F52-; (D5h), TeOF62-; (C5v), TeF7-; (D5h), TeF82-; (D4d) and IF8-; (D4d). 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.