Structural characterization of hypervalent fluoride and oxofluoride derivatives of xenon and tellurium and iodine

Abstract

The study of fluoro- and oxofluoro-anions and cations having coordination numbers higher than six has been of particular interest and is exemplified by the fluoride ion donor and electron pair acceptor properties of the oxofluorides of xenon. The X-ray crystal structure of XeOF 3 +SbF 6 − has been determined. The XeOF 3 + cation is shown to have two fluorine bridges to neighboring SbF 6 − anions, resulting in an AX 6E VSEPR arrangement around xenon in the solid state. The solution 17O NMR spectrum along with the 17O/ 18O isotope shift ratio in the 129Xe spectrum of the XeOF 3 + cation have also been obtained. The fluoride ion donor properties of XeOF 2 and the formation of the XeOF + cation are also discussed. The electron pair acceptor properties of XeOF 4, XeOF 2 and XeO 3 in the presence of nitrogen bases have been investigated by NMR spectroscopy. The XeOF 4·CH 3CN adduct has been isolated as a crystalline solid and its structure also appears to be best represented as a distorted octahedral (AX 6E) arrangement. In collaboration with Dr. K.O. Christe and Dr. W.W. Wilson (Rockwell International), a number of hypervalent anions having coordination numbers exceeding six have been prepared and characterized. The IOF 6 − anion has been characterized as its N(CH 3) 4 + salt by X-ray crystallography, vibrational spectroscopy and in solution by NMR spectroscopy. The X-ray structure shows that the anion is distorted from C 5v point symmetry by means of a puckering of the five fluorines in its equatorial plane. The structures of the N(CH 3) 4 + salts of the TeOF 6 2−, XeOF 5 −, XeF 7 − and TeF 7 − anions will also be described. The Lewis acid properties of XeF + and XeOTeF 5 + have been investigated in the presence of the nitrogen base F 5TeNH 2. The novel XeN bonded F 5TeN(H)Xe + and F 5TeN(H)XeNCH + cations have been synthesized in anhydrous HF and characterized by 1H, 15N, 19F, 125Te and 129Xe NMR spectroscopy.