Halides, binary reactions

An attempt has been made here to investigate certain reactions of radiation-chemical syntheses in the condensed phase (10). One component in all our binary reaction systems was the RHal (alkyl halide), while the other was represented by a free element (tin, nitrogen, or chlorine) of the IVth, Vth or the Vllth group of the periodic chart. As expected, the nature of the latter component most strongly influenced the character and the parameters of the radiation processes examined. 

A summary of the vapor complexes formed in rare-earth halide/alkali halide binary systems according to the general reaction scheme (1) (sect. 1.1) is given in the present section. Studied systems involving divalent metal halides include only the ScCl3-MgCl2... 

Low-temperature solvents are not readily available for many refractory compounds and semiconductors of interest. Molten salt electrolysis is utilized in many instances, as for the synthesis and deposition of elemental materials such as Al, Si, and also a wide variety of binary and ternary compounds such as borides, carbides, silicides, phosphides, arsenides, and sulfides, and the semiconductors SiC, GaAs, and GaP and InP [16], A few available reports regarding the metal chalcogenides examined in this chapter will be addressed in the respective sections. Let us note here that halide fluxes provide a good reaction medium for the crystal growth of refractory compounds. A wide spectrum of alkali and alkaline earth halides provides... 

It has been shown for many metal halides and monomers that binary mixtures of these can be prepared (usually in a solvent) without any polymerization taking place. Such a quiescent mixture can be made to react by the addition of a suitable third compound, which is called the co-catalyst. This term is preferable to the word promoter , because in certain contexts a substance is called promoter which enhances the rate or yield of a reaction that will also go in the absence of the promoter herein lies the true distinction between promoter and co-catalyst [28]. (For example, small quantities of epoxides or epichlorohydrin act as promoters in the cationic polymerization of tetrahydrofuran.) I will take it that in the above quotation the word promoter was inadvertently used in place of co-catalyst , for only thus does it become really meaningful. 

Binary Compounds. The thermodynamics of the formation of HfCl2, of HfCl4, fused sodium and potassium chlorides have been described. The reduction of ZrXj (X = Cl, Br, or I) with metallic Zr or A1 in molten AICI3 has been studied at temperatures from 250 to 360 °C, depending on the halide. The electronic spectra of the initial reaction products were consistent with either a solvated Zr complex or an intervalence Zr "-Zr" species. Further reduction resulted in the precipitation of reduction products which were identified by analysis and i.r., electronic, and X-ray powder diffraction spectra. The stability of the trihalides with respect to disproportionation was observed to increase from chloride to iodide thus ZrC and ZrCl2,0.4AlCl3 were precipitated, whereas only Zrlj was formed. ... 

Tellurium forms binary teUurides with several metals. The reaction is carried out by heating tellurium with a metal in stoichiometric amounts in the absence of air in an evacuated ampoule. Tellurium reacts with halides of several metals, when heated in a stream of hydrogen, to produce metal tel-lurides. 

Thallium burns in fluorine with incandescence. Reactions with other halogens form halides. Thallium combines with several elements forming binary compounds. 

Germanes hydride, 2 76 reactivity of, 2 87 Germanium anionic cluster, 24 227 azides, preparation, 9 138 properties, 9 135-136, 139, 141 binary carbide not reported, 11 211 carbides, preparation of, 11 163 chalcogenide halides, 23 390 chlorides, mass spectra of, 18 248, 249 complexes, xenon fluoride reactions, 46 85 compounds, see also Organogermanium compounds... 

Halides, 7 1-26 actinide elements, 2 195-233 anion dependence, 39 139 berkelium, 28 48, 51-53 beryllium, 14 255-332 binary, 35 237-246, 274-280 decomposition, 35 277 dichalcogen dihalides, 35 279-280 equilibrium studies, 35 242 mixed-ligand halides, 35 244-246 reactions, 35 246 selenium halides, 35 240-241... 

No systematic study has been made to complete the list of substances given below. The reader is invited to look for further examples. The chalcogenide halides are formed by reaction of mixtures of the respective elements or binary components, or both, in the appropriate hydrogen halide acid under hydrothermal conditions. Temperatures are in the range of 500-100°C. The densities of the fluid are at least 55% of room-temperature values the corresponding pressures are not known in most cases. 

The most obvious route to a binary compound ExE y is the direct interaction between the elemental substances E and E. This is often precluded by thermodynamic considerations however, a great many compounds that are unstable with respect to the elemental substances are kinetically stable and can be prepared by other means. Even if the reaction between the elemental substances is possible, both from thermodynamic and kinetic viewpoints, an indirect synthesis may be preferable for practical reasons. We shall illustrate these principles by looking at some examples of synthetic routes to binary hydrides and halides. 

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