Fluoride chlorides

Halide derivatives may be fluorides, chlorides, or bromides. Fluorides are best prepared by the reaction of hydroxy groups with (diethylamino)sulfur trilluoride ( DAST M. Sharma, 1977) or of glycosyl thioethers with DAST/NBS (K.C. Nicolaou, 1990 B). The other halides are usually only introduced at the glycosidic position, where treatment with hydrogen chloride... 

The lUPAC rules permit alkyl halides to be named m two different ways called func twnal class nomenclature and substitutive nomenclature In functional class nomencla ture the alkyl group and the halide (fluoride chloride bromide or iodide) are desig nated as separate words The alkyl group is named on the basis of its longest continuous chain beginning at the carbon to which the halogen is attached... 

X in acid derivatives Name of X (in priority order fluoride, chloride, bromide, iodide, cyanide, azide then the sulfur and selenium analogs)... 

Uses. Lithium fluoride is used primarily in the ceramic industry to reduce firing temperatures and improve resistance to thermal shock, abrasion, and acid attack (see Ceramics). Another use of LiF is in flux compositions with other fluorides, chlorides, and borates for metal joining (17) (see Solders). 

Coordination Complexes. The abiUty of the various oxidation states of Pu to form complex ions with simple hard ligands, such as oxygen, is, in order of decreasing stabiUty, Pu + > PuO " > Pu + > PuO Thus, Pu(Ill) forms relatively weak complexes with fluoride, chloride, nitrate, and sulfate (105), and stronger complexes with oxygen ligands (Lewis-base donors) such as carbonate, oxalate, and polycarboxylates, eg, citrate, and ethylenediaminetetraacetic acid (106). The complexation behavior of Pu(Ill) is quite similar to that of the light lanthanide(Ill) ions, particularly to Nd(Ill)... 

Titanium oxidation state Fluoride Chloride Bromide Iodide... 

The i5p-titanium(IV) atom is hard, ie, not very polarizable, and can be expected to form its most stable complexes with hard ligands, eg, fluoride, chloride, oxygen, and nitrogen. Soft or relatively polarizable ligands containing second- and third-row elements or multiple bonds should give less stable complexes. The stabihty depends on the coordination number of titanium, on whether the ligand is mono- or polydentate, and on the mechanism of the reaction used to measure stabihty. 

S-Alkylthiiranium salts, e.g. (46), may be desulfurized by fluoride, chloride, bromide or iodide ions (Scheme 62) (78CC630). With chloride and bromide ion considerable dealkylation of (46) occurs. In salts less hindered than (46) nucleophilic attack on a ring carbon atom is common. When (46) is treated with bromide ion, only an 18% yield of alkene is obtained (compared to 100% with iodide ion), but the yield is quantitative if the methanesulfenyl bromide is removed by reaction with cyclohexene. Iodide ion has been used most generally. Sulfuranes may be intermediates, although in only one case was NMR evidence observed. Theoretical calculations favor a sulfurane structure (e.g. 17) in the gas phase, but polar solvents are likely to favor the thiiranium salt structure. 

Fluoride < chloride < bromide = iodide = acetate < molybdate < phosphate < arsenate < nitrate < tartrate < citrate < chromate < sulfate < hydroxide. 

Oxidation state Fluorides Chlorides Bromides Iodides... 

The other anhydrous FeX3 can be prepared by heating the elements (though in the case of FeBr3 the temperature must not rise above 200°C otherwise FeBr2 is formed). The fluoride, chloride and bromide are respectively white, dark... 

Interaction between niobium oxide and fluorides, chlorides or carbonates of alkali metals in an ammonium hydrofluoride melt, yielded monooxyfluoroniobates with different compositions, MxNbOF3+x, where they were subsequently investigated [123-127]. According to DTA patterns of the Nb205 - 6NFL HF2 - 2MF system, (Fig. 18) a rich variety of endothermic effects result from the formation of ammonium monooxyfluoroniobate, its thermal decomposition and its interaction with alkali metal fluorides. The number of effects decreases and separation of ammonium ceases at lower temperatures and when going from lithium to cesium in the sequence of alkali metal fluorides. 

Analysis of the melting diagrams led to the conclusion that fluoride, fluoride-chloride and oxyfluoride-chloride melts containing niobium contain the complex ions NbF83 NbF7Cl3 Nb02F43 ... 

An analysis of the melting diagram led to the conclusion that, in fluoride and fluoride-chloride melts, tantalum forms the complex ions TaFg3 or TaF7Cl3, respectively [37,306]. 

Only two processes of tantalum metal production are of worldwide commercial significance. These are the electrolysis of fluoride-chloride melts containing potassium heptafluorotantalate, K TaF , and tantalum oxide, Ta20s, and the reduction with sodium of K-salt or K—salt that is dissolved in potassium fluoride-chloride melts. 

A similar electrolyte, containing potassium heptafluoroniobate, K2NbF7, can be used for the electrolytic reduction of niobium [37, 542 - 544]. No industrial application, however, was found for the electrolysis of niobium in fluoride-chloride melts. 

The majority of researchers, however, are inclined to believe that the tantalum reduction process takes place in a single step. Experimental results and discussions confirm that tantalum is reduced from fluoride, fluoride-chloride and oxyfluoride melts containing K2TaF7, via a single stage in which five electrons are transfered [546 - 548] ... 

Niobium undergoes a two-stage electrochemical reduction from potassium heptafluoroniobate, K2NbF7, that is dissolved in fluoride-chloride melts [550 -553] ... 

The anionic composition of the cathodic product is not the only parameter that can be controlled through electrolysis conditions. Grinevitch et al. [559] reported on the investigation of the co-deposition of tantalum and niobium during the electrolysis of fluoride - chloride melts. Appropriate electrodeposition conditions were found that enable to obtain either pure niobium or alloys. 

Similar results were reported by Freidin et al. [568]. Moreover, a correlation was reported [360] between the particle size of tantalum powder obtained by electrolysis of fluoride - chloride melts and its electric conductivity. 

Cation fluoride chloride bromide iodide hydroxide carbonate sulfate nitrate... 

Goldschmidt predicted from his empirical rule that calcium chloride would not have the fluorite structure, and he states that on investigation he has actually found it not to crystallize in the cubic system. Our theoretical deduction of the transition radius ratio allows us to predict that of the halides of magnesium, calcium, strontium and barium only calcium fluoride, strontium fluoride and chloride, and barium fluoride, chloride,... 

In the case of molten salts, the functional electrolytes are generally oxides or halides. As examples of the use of oxides, mention may be made of the electrowinning processes for aluminum, tantalum, molybdenum, tungsten, and some of the rare earth metals. The appropriate oxides, dissolved in halide melts, act as the sources of the respective metals intended to be deposited cathodically. Halides are used as functional electrolytes for almost all other metals. In principle, all halides can be used, but in practice only fluorides and chlorides are used. Bromides and iodides are thermally unstable and are relatively expensive. Fluorides are ideally suited because of their stability and low volatility, their drawbacks pertain to the difficulty in obtaining them in forms free from oxygenated ions, and to their poor solubility in water. It is a truism that aqueous solubility makes the post-electrolysis separation of the electrodeposit from the electrolyte easy because the electrolyte can be leached away. The drawback associated with fluorides due to their poor solubility can, to a large extent, be overcome by using double fluorides instead of simple fluorides. Chlorides are widely used in electrodeposition because they are readily available in a pure form and... 

Numerous compounds adopt the PbFCl structure. These include, apart from fluoride chlorides, oxide halides MOX (M = Bi, lanthanoids, actinoids X = Cl, Br, I), hydride halides like CaHCl and many compounds with metallic properties like ZrSiS or NbSiAs. 

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