Oxyhalides preparation

Niobium Halides and Oxyhalides. AH possible haUdes of pentavalent niobium are known and preparations of lower valent haUdes generally start with the pentahaUde. Ease of reduction decreases from iodide to fluoride. 

Halides and Oxyhalides. Vanadium(V) oxytrichloride is prepared by chloriaation of V20 mixed with charcoal at red heat. The tetrachloride (VCl is prepared by chlorinating cmde metal at 300°C and freeing the Hquid from dissolved chlorine by repeated freezing and evacuation. It now is made by chlorinating V20 or VOCl ia the presence of carbon at ca 800°C. Vanadium trichloride (VCl ) can be prepared by heating VCl ia a stream of CO2 or by reaction of vanadium metal with HCl. 

A number of gaseous oxyhalides of nitrogen are known, including the types XNO (nitrosonium or nitrosyl halides) with X = F, Cl, or Br, and XN02 (nitryl halides) with X = F or Cl. Nitrosonium halides are prepared by the reactions of halogens and NO. 

Thorium metal, 24 759-761 in alloys, 24 760-761 preparation of, 24 759-760 properties of, 24 760-761 reactions of, 24 761 Thorium nitrate, 24 757, 766 Thorium oxalates, 24 768-769 Thorium oxide, 21 491 Thorium oxides, 24 757, 761-762 Thorium oxyhalides, 24 762 Thorium perchlorate, 24 764 Thorium phosphates, 24 765-766 Thorium pnictides, 24 761 Thorium sulfate, 24 764 Thorium-uranium fuel cycle, 24 758-759 Thorocene, 24 772 Thorotrast, 24 775-776 3A zeolite. See Zeolite 3A Three-boiling beet sugar crystallization scheme, 23 463-465 Three-color photography, 19 233-234 3D models, advantages of, 19 520-521 3D physical design software, 19 519-521 3D QSAR models, 10 333. See also QSAR analysis... 

Halides and Oxyhalides. Molecules of VCI2, prepared by Knudsen cell techniques, have been isolated in solid inert-gas matrices and their i.r. spectra indicate a linear structure. However, similar studies suggested that VF2 molecules are non-linear. The d d spectrum of gaseous VCI2 has been discussed in terms of ligand field theory, and the Tanabe-Sugano matrix for a linear d system presented. ... 

Oxygenic photosynthetic organisms, [2Fe-2S] ferredoxins, 38 224-233 Oxygenyl ion, preparation of, 9 229 Oxyhalides, of berkelium, 28 49, 51-53 Oxyhalogeno cations, 9 276-279 Oxyhemerythrin, 40 373-374, 45 84 XAS, 36 325 Oxyhemocyanin, 40 363 m-peroxo dinuclear copper complexes as models for, 39 41-52 physicochemical properties, 39 47-48 Oxyhemocyanins, XAS, 36 326-327 Oxyhemoglobin, 21 135 Oxyiodonium cations, 9 277 Oxymanganese phthalocyanine, strucmre of, 7 31-35... 

Compounds of the formulas Re(CH3)6, ReO(CH3)4, Li e CH ] [60975-25-9], Re02(CH3)3 [56090-011-8], and Re03CH3 [70197-13-6] have been prepared. The first two compounds were obtained from reaction of rhenium halides or oxyhalides and methyllithium the last three were formed from the species by oxidation or reduction reactions. The use of these hydride and alkyl complexes as catalysts is under investigation. 

Tellurium Halides. Tellurium forms the dihalides TeCl and TeBi, but not Tel2. However, it forms tetrahalides with all four halogens. Tellurium decafluoride [53214-07-6] and hexafluoride can also be prepared. No monohalide, Te2X2, is believed to exist. Tellurium does not form well-defined oxyhalides as do sulfur and selenium. The tellurium halides show varying tendencies to form complexes and addition compounds with nitrogen compounds such as ammonia, pyridine, simple and substituted thioureas and anilines, and ethylenediamine, as well as sulfur trioxide and the chlorides of other elements. 

Three oxide halides T10X (X = F, Cl, Br) are known.1 Preparations must be carried out at low temperatures1 387 since the heavier oxyhalides in particular readily decompose. There is no structural information on either TlOCl br TlOBr, but X-ray crystallography shows that TlOF has a calcium fluoride structure, with Tl3+ ions in a cube of F" or 02 ions.388... 

Antimony forms polymeric oxyhalides, and not metallic as in BiOCl. The fluoride, SbOF, has been prepared in two forms V, with a ladder structure, and iM which has a layered structure. Both forms have a trigonal bipyramidal structure about antimony with three oxygens, one fluorine and one lone pair. Structural parameters are given in Table 15, from which it can be seen that L-SbOF heads the table as the nearest to an ideal fit for trigonal bipyramidal geometry. 

The synthetic routes available for the preparation of the known oxyhalides, listed in Table 19, range from the halogenation of the oxides to the carefully controlled reaction of the halides with dioxygen. 

Of the oxyhalides of Wv, both [WOCl3] and [WOBr3] are known. These can be prepared by reduction of [WOX4]161 or by the reaction of WX5 with Sb203162 as depicted in equation (6). 

Since fluorine is difficult to prepare and manipulate, the anhydrous fluorides and oxyfluorides are prepared by the action of anhydrous hydrogen fluoride on other halides or oxyhalides of vanadium.1... 

The pentavalent halides and oxyhalides, as in the case of other niobium compounds, are the most stable. It is remarkable that the pentavalency is maintained with increase in the atomic weight of the halogen. All the halogen compounds are characterised by their ready tendency to undergo hydrolysis on the addition of water or even in damp air with precipitation of niobie acid and formation of the hydrogen halide. Their preparation can, therefore, be effected only in the dry way (a) synthetically, or (b) by the action of chlorine, carbon tetrachloride, or sulphur monochloride on the oxide or sulphide. They do not possess saline properties, and cannot be prepared by the action of the halogen acids on the oxide. 

The hydrated trihalides of the rare earths are easily obtained by reacting the oxides with appropriate HX acid solution. Anhydrous halides are, however, difficult to prepare. Attempts to dehydrate the hydrated halides usually result in oxyhalides. In the case of the chlorides and bromides... 

All of die halides except tile hexafluoride and the triiodide may be prepared by the hydrohalogenation of rhe dioxide or of the oxalate of plutonium(lll) at a temperature of about 700°C. With hydrogen fluoride the reaction product is PUF4, unless hydrogen is added to the gas stream, in which case the trifluoride is produced. With hydrogen iodide the reaction product is PuOi, and the other oxyhalides may be formed by the addition of appropriate quantities of water vapor to the hydrogen halide gas. Plutonium triiodide is produced by the reaction of the metal with hydrogen iodide at about 400°C. The hexafluoride is produced by direct combination of the... 

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