Tetrafluoride ion

The best-studied aqueous actinide halide systems are the fluorides and the chlorides. Fluoride and chloride ions are added to the actinyl centers in a stepwise fashion (Scheme 4). The end member in the actinyl fluoride system is the pentafluoride, An02F5 . For the uranyl analog, the U = O and U-F bond distances were found to be 1.79 and 2.18A respectively. The uranium tetrafluoride ion, U02F4 , has been isolated as a dimer with two bridging fluoride ligands. The U = O, U-Fterminai, uud U-Fbridging distauces for this complex were found to be 1.79, 2.15 to 2.20 A, and 2.30 A, respectively. 

In addition to free radical polymerizations, however, cationic and anionic polymerizations may, depending on solvent used, also be observed. The anodic discharge of acetate ions into the homogeneous phase, for example, produces a free radical polymerization of styrene or acrylonitrile. The anodic discharge of perchlorate or boron tetrafluoride ions, on the other hand, leads to the cationic polymerization of styrene, iV-vinyl carbazole, and isobutyl vinyl ether. In contrast, the cathodic decomposition of tertaalkyl ammonium salts induce acrylonitrile to polymerize anionically. 

Halide donor-acceptor reactions (of XX ) are generally those in which X is donated to or accepted from an interhalogen. They include self-ionization reactions such as that of BrF3 shown in Equation (18.53). This property makes bromine trifluoride a common aprotic (without protons) self-ionizing solvent. In addition to its self-ionization, BrF3 readily accepts fluoride ions from other sources, such as alkali-metal fluorides, to produce salts containing the bromine tetrafluoride ion, as shown in Equation (18.54). Conversely, it can donate fluoride ions to produce salts containing the bromine difluoride cation, as shown in Equation (18.55). 

Vanadium tetrafluoride, VF4. Green solid prepared HF on VCI4. Forms hexa-fluorovanadate(IV) ion (VFa) ". VOF2 formed by hydrolysis. 

In the geochemistry of fluorine, the close match in the ionic radii of fluoride (0.136 nm), hydroxide (0.140 nm), and oxide ion (0.140 nm) allows a sequential replacement of oxygen by fluorine in a wide variety of minerals. This accounts for the wide dissemination of the element in nature. The ready formation of volatile silicon tetrafluoride, the pyrohydrolysis of fluorides to hydrogen fluoride, and the low solubility of calcium fluoride and of calcium fluorophosphates, have provided a geochemical cycle in which fluorine may be stripped from solution by limestone and by apatite to form the deposits of fluorspar and of phosphate rock (fluoroapatite [1306-01 -0]) approximately CaF2 3Ca2(P0 2 which ate the world s main resources of fluorine (1). 

Germanium forms both a difluoride and a tetrafluoride. It also forms a stable hexafluorogermanate complex ion, GeF that is present in the aqueous acid and a number of salts. 

Uses. The chemical inertness, thermal stability, low toxicity, and nonflammability of PFCs coupled with their unusual physical properties suggest many useflil applications. However, the high cost of raw materials and manufacture has limited commercial production to a few, small-volume products. Carbon tetrafluoride and hexafluoroethane are used for plasma, ion-beam, or sputter etching of semiconductor devices (17) (see loN implantation). Hexafluoroethane and octafluoropropane have some applications as dielectric gases, and perfluorocyclobutane is used in minor amounts as a dielectric fluid. Perfluoro-1,3-dimethyl cyclohexane is used as an inert, immersion coolant for electronic equipment, and perfluoro-2-methyldecatin is used for... 

Xenon tetrafluoride is a much weaker fluoride ion donor and only forms stable complex salts with the strongest fluoride ion acceptors, eg,... 

In TBP extraction, the yeUowcake is dissolved ia nitric acid and extracted with tributyl phosphate ia a kerosene or hexane diluent. The uranyl ion forms the mixed complex U02(N02)2(TBP)2 which is extracted iato the diluent. The purified uranium is then back-extracted iato nitric acid or water, and concentrated. The uranyl nitrate solution is evaporated to uranyl nitrate hexahydrate [13520-83-7], U02(N02)2 6H20. The uranyl nitrate hexahydrate is dehydrated and denitrated duting a pyrolysis step to form uranium trioxide [1344-58-7], UO, as shown ia equation 10. The pyrolysis is most often carried out ia either a batch reactor (Fig. 2) or a fluidized-bed denitrator (Fig. 3). The UO is reduced with hydrogen to uranium dioxide [1344-57-6], UO2 (eq. 11), and converted to uranium tetrafluoride [10049-14-6], UF, with HF at elevated temperatures (eq. 12). The UF can be either reduced to uranium metal or fluotinated to uranium hexafluoride [7783-81-5], UF, for isotope enrichment. The chemistry and operating conditions of the TBP refining process, and conversion to UO, UO2, and ultimately UF have been discussed ia detail (40). 

I Self-Test 2.10B Write the lewis structure for the l ion and give the number of 25 Xenon tetrafluoride, XeF4 I electrons in the expanded valence shell. 

Xenon fluorides, 77 323-325 binary, 77 335-336 Xenon-gold cations, 77 332 Xenon halides, 77 323-325 Xenon hexafluoride, 7 7 325, 329 uses for, 7 7 336 Xenon ion lasers, 74 685 Xenon isotopes, in fission reactors, 77 375 Xenon oxide difiuoride, 77 326 Xenon oxide fluorides, 7 7 326 Xenon oxides, 77 325-326 Xenon oxide tetrafluoride, 77 326 Xenon testing, in plastics weathering, 79 584-585... 

Probably also connected with the size of Me-ions is the collinear array of linked octahedra e. g. in the pentafluorides of Nb, Ta and Mo (page 27), whereas angles occur in those of the RuFs-type (page 27). Similar conditions may be expected in tetrafluorides, but only the linear case of the NbF4-type is known so far (page 31). 

Cerium phthalocyanine, 7 64 Cerium tetrafluoride, 20 63-67 lattice parameters, 20 64 Cerium trifluoroacetates, 17 5, 26 Cermets, nitrides in, 9 81-82 Cerous ion, reaction with hydroxyl ions, 3 187 Ceruloplasmin, 40 123, see also Blue copper oxidases... 

Crystallographic data (.continued) for transition metal tetrafluorides, 27 98 for transition metal trifluorides, 27 92 Crystallographic disorder, nitrosyl groups, 34 304-305 Crystallography fuscoredoxin, 47 380 prismane protein, 47 232-233 Rieske and Rieske-type proteins, 47 92-109 Crystal radii, of various ions, 2 7 Crystals, 39 402 Crystal structure actinide metals, 31 36 copper-cobalt supetoxide dismutases, 45 ... 

A white solid, possibly polonium tetrafluoride, is obtained by treating polonium hydroxide or tetrachloride with dilute aqueous hydrofluoric acid treatment of this solid, in suspension in dilute hydrofluoric acid, with sulfur dioxide yields a bluish grey product (possibly PoF2) which rapidly reverts to the original white solid on standing, presumably owing to radio-lytic oxidation 12). The solubility of polonium(IV) in aqueous hydrofluoric acid increases rapidly with acid concentration, indicating complex ion formation (/ft), p. 48). 

There have been some unsuccessful attempts to prepare a volatile hexafluoride from fluorine and polonium-210 26, 104), but recently such a fluoride has been prepared in this way from polonium-208 plated on platinum 132). The product appears to be stable while in the vapor phase, but on cooling a nonvolatile compound is formed, probably polonium tetrafluoride resulting from radiation decomposition of the hexafluoride. Analytical data are not recorded for any polonium fluoride, largely owing to the difficulty of determining fluoride ion accurately at the microgram level. 

The first long-lived fluorine-containing carbocation was discovered by Olah and coworkers.32 Thus, the fluorodimethylcarbcnium ion [Me2CF+] was obtained by protonation of 2-fluoropropene and also from 2,2-difluoropropane by reaction with antimony(V) fluoride. In the course of these investigations it was found that a-F stabilizes a cationic state, whereas fi-F is destabilizing. Attempts to prepare the simplest member of this class, the trifluoromethyl carbocation CF3+ failed. The ionization of trifluoromethyl halides with antimony(V) fluoride at — 80 C yielded only carbon tetrafluoride. 

The most intense bands, as well as overtone bands at 1744 and 1281 cm"1, are used as purity probes for sulfur tetrafluoride.9 The mass spectrum of sulfur tetrafluoride shows a weak molecular peak and strong fragmentation peaks corresponding to SF/, SF2+, SF+ and F+ ions.10... 

Support for the participation of fluorocarbenium ions 2 in the above mechanism is provided by trapping with aromatic hydrocarbons in the reaction of sulfur tetrafluoride with haloacetic acids, c.g. formation of 4,36 and haloacetones.37... 

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