Hexafluoride complexes

Another class of octahedral structures whose stereochemistry was established by NMR is tungsten hexafluoride complexes with donor molecules, e.g., WF6-(C6H6)3P (87a). For these, the F19 spectra consist of a low-field doublet, a medium-field quintet and a high-field singlet of relative intensities 4 1 1. The doublet and quintet resonances establish the geometry... 

Extensive work has been done on the hyperfine interaction of the hexafluoride complexes of several transition ions (29, 39-45). To illustrate the approach used in interpreting the superhyperfine interaction, we shall consider the case of the ds configuration of Mn2+ and Fe3+. For this case we have an 6S-state ion with each d orbital singly occupied. The equations for the five antibonding MO s are... 

Allen, G. C. Warren, K. D. (1971) Electronic spectra of hexafluoride complexes. Struct. Bonding, 9,49-138. 

Tellurium dioxide complexes with thiourea, 305 Tellurium dithiocyanate complexes, 303 Tellurium hexafluoride complexes, 303 with amines, 304 Tellurium sulfate complexes, 303 Tellurium tetrabromide complexes, 302 Tellurium tetrachloride complexes with acetamide, 304 with amines, 304 with pyridine N-oxide, 304 Tellurium tetrafluoride complexes with amines, 304 with dioxane, 304 Tellurotungstates, 1042 Tempera ture-jump studies molybdenum(VI) complexes, 1259 Terbium complexes p diketones, 1081... 

A convenient preparatory method is to form the tertiary phosphine molybdenum hexafluoride complex in methylene chloride at -60°C. On heating such complexes, R3PF2-type compounds are liberated (6.510). Hydrogen fluoride adds to alkylphosphonous dihalides (6.511). Fluorophosphoranes are also obtained from diphosphines (6.538 below), or by halogenation of R2NPF2 -type compounds (7.107). 

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). 

Uranium hexafluoride [7783-81-5], UF, is an extremely corrosive, colorless, crystalline soHd, which sublimes with ease at room temperature and atmospheric pressure. The complex can be obtained by multiple routes, ie, fluorination of UF [10049-14-6] with F2, oxidation of UF with O2, or fluorination of UO [1344-58-7] by F2. The hexafluoride is monomeric in nature having an octahedral geometry. UF is soluble in H2O, CCl and other chlorinated hydrocarbons, is insoluble in CS2, and decomposes in alcohols and ethers. The importance of UF in isotopic enrichment and the subsequent apphcations of uranium metal cannot be overstated. The U.S. government has approximately 500,000 t of UF stockpiled for enrichment or quick conversion into nuclear weapons had the need arisen (57). With the change in pohtical tides and the downsizing of the nation s nuclear arsenal, debates over releasing the stockpiles for use in the production of fuel for civiUan nuclear reactors continue. 

Electroplating. Aluminum can be electroplated by the electrolytic reduction of cryoHte, which is trisodium aluminum hexafluoride [13775-53-6] Na AlE, containing alumina. Brass (see COPPERALLOYS) can be electroplated from aqueous cyanide solutions which contain cyano complexes of zinc(II) and copper(I). The soft CN stabilizes the copper as copper(I) and the two cyano complexes have comparable potentials. Without CN the potentials of aqueous zinc(II) and copper(I), as weU as those of zinc(II) and copper(II), are over one volt apart thus only the copper plates out. Careful control of concentration and pH also enables brass to be deposited from solutions of citrate and tartrate. The noble metals are often plated from solutions in which coordination compounds help provide fine, even deposits (see Electroplating). 

Molybdenum hexafluoride. 3,1412 Molybdenum-iron-sulfur complexes, 4,241 Molybdenum oxide amino acid formation prebiotic systems, 6, 872 Molybdenum storage protein microorganisms, 6, 681 Molybdenum telluride, 3, 1431 Molybdenum tetraalkoxides physical properties, 2, 347 Molybdenum tribromide, 3,1330 Molybdenum trichloride, 3,1330 Molybdenum trifluoride, 3, 1330 Molybdenum trihalides, 3, 1330 bond lengths, 3, 1330 magnetic moments, 3,1330 preparation, 3,1330 properties, 3, 1330 structure, 3,1330 Molybdenum triiodide, 3,1330 Molybdenum trioxide complexes, 3, 1379 Molybdenum triselenide, 3, 143)... 

The starting point for the synthesis of xenon compounds is the preparation of xenon difluoride, XeF2, and xenon tetrafluoride, XeF4, by heating a mixture of the elements to 400°C at 6 atm. At higher pressures, fluorination proceeds as far as xenon hexafluoride, XeFfi. All three fluorides are crystalline solids (Fig. 15.27). In the gas phase, all are molecular compounds. Solid xenon hexafluoride, however, is ionic, with a complex structure consisting of XeF< + cations bridged by F anions. 

Analysis of the halohydrocarbons, halocarbons, and sulfur hexafluoride is usually achieved by gas chromatography that is equipped with an electron capture detector. Complex metal anions, such as cobalt hexacyanide, are used as nonradioactive tracers in reservoir studies. The cobalt in the tracer compound must be in the complex anion portion of the molecule, because cationic cobalt tends to react with materials in the reservoir, leading to inaccurate analytic information [1226]. 

The compounds containing the hexahalogen complexes [IrCle], [IrBrs] with Ir(lV) formal oxidation state and iridium hexafluoride with hexavalent... 

Uranium halide complexes, 25 437-439 physical constants for, 25 4371 Uranium hexachloride, 25 439 Uranium hexafluoride, 11 845, 859, 25 438 Uranium hydrocarbyl complexes,... 

As in the hexafluorides there are finite octahedral groups in the structures of the described hexafluorometallates too, one isolated from the other and thus hardly influenced by it. This brings about the character of complex anions, as may be seen from the shrinking of distances Me—F and F—F within the MeFg-group, often below the ionic radii sum. 

Hexadiene complexes with gold, 12 348 with iron, 12 263, 264 with platinum, 12 319 with rhodium, 12 297-299 with silver, 12 340 Hexafluorides, structures, 27 106-108 Hexafluoroacetone, 30 223-312, 44 317-318 metal complexes, 30 279-298 of cobalt, 30 286-287 of gold, 30 295... 

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