Selenium tellurium halides

The first compound of this series, CeSI, was reported by Carter (68) in 1961, and later discussed by Dagron (93). It was obtained by the reaction of iodine with cerium sulfide at 430 C, or by direct synthesis from the elements at 500°C. This was the start of a detailed investigation of this group of compounds mainly by Dagron and co-workers. The present situation is presented in Table VII. No scandium compounds are known thus far, and the same is true for selenium and tellurium halides of these elements. 

Oxyacids containing selenium and tellurium are known, but they and their salts are generally less important than the sulfur compounds. When selenium and tellurium halides hydrolyze, the solutions contain selenous and tellurous acids. 

Selenium- and Tellurium-Nitrogen Halides. The best characterised selenium-nitrogen halide is the cation [863X20 ] (12.26), which forms a... 

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. 

The other halides of boron and silicon, and also of, phosphorus, sulphur, selenium, tellurium, and iodine, react at once with water, forming hydrogen halide and an acid. The equations are as follows —... 

Similar trans effect correlations have also been observed for related selenium and tellurium halide complexes by Knop and coworkers and by Krebs and Ahlers (19) a number of structural similarities between group 16 halides and halogenoanions are evident and these are mentioned where appropriate in the following section. 

Selenium and Tellurium Halides. For selenium, these halides are mostly of marginal stability and the characterization is incomplete the most stable ones are Se2Cl2 and Se2Br2, whose structures are known. In acetonitrile there are the following equilibria ... 

Phenyl tellurium halides, generated from diphenyl ditellurium and halogen in the presence or absence of thiourea, reacted with potassium selenocyanate to give bis phenyltelluro selenium. ... 

A similar exchange reaction produced the 1 1 complexes of phenyl tellurium thiocyanate with ethylenethiourea when the phenyl tellurium chloride complex was treated with potassium thiocyanate in aqueous methanol. However, the phenyl tellurium chloride -selenourea adduct and potassium selenocyanate yielded bis[phenyltelluro] selenium. Phosphane selenides also coordinate to phenyl tellurium halides. ... 

Reduction of Organoselenium and -tellurium Halides and Oxides. TUD reduces aryltellurium trihalides to diaryl ditel-lurides (eq 2) and diorganyltellurium dihalides and telluroxides to diorganyl tellurides (eq 3) in high yield. The corresponding selenium compounds are reduced similarly. Some examples are given in Table 2. The reduction is performed by premixing the substrate and 2 N NaOH at room temperature for 15 min prior to the addition of TUD in petroleum ether. 

Sulphenyl Halides.—This section describes first the preparations of sulphenyl halides of particular interest in the recent literature, then their properties and their addition and substitution reactions. More space is allocated this year for results from studies of organo-sulphur, -selenium, and -tellurium halides involving higher valency states. 

Ylides of Sulphur, Selenium, Tellurium, and Related Structures 341 halide ion present and the NaOH concentration." Under phase-transfer-catalysed conditions, involving methylene chloride and water solvents, sodium hydroxide as the base, and tetrabutylammonium iodide as a transfer agent, trimethylsulphonium iodide and benzaldehyde afforded a 90% yield of styrene oxide." An equally good yield was obtained with cinnamal-dehyde, but low yields were obtained with acetophenone and benzo-phenone. 

The halides formed by selenium, tellurium and polonium are summarized in Table 12.5. Table 12.5 The halides of selenium, tellurium and polonium... 

Oxygen halides are dealt with in Chapter 11, p. 334. Sulphur, selenium and tellurium form many halides, and only a brief introduction to the subject is given here. 

Nitrogen and sodium do not react at any temperature under ordinary circumstances, but are reported to form the nitride or azide under the influence of an electric discharge (14,35). Sodium siHcide, NaSi, has been synthesized from the elements (36,37). When heated together, sodium and phosphoms form sodium phosphide, but in the presence of air with ignition sodium phosphate is formed. Sulfur, selenium, and tellurium form the sulfide, selenide, and teUuride, respectively. In vapor phase, sodium forms haHdes with all halogens (14). At room temperature, chlorine and bromine react rapidly with thin films of sodium (38), whereas fluorine and sodium ignite. Molten sodium ignites in chlorine and bums to sodium chloride (see Sodium COMPOUNDS, SODIUM HALIDES). 

Despite the tremendous amount of work on the binary compounds, copper chalcogenide halides were first reported in 1969 (304). Nine compounds of selenium and tellurium have been found, and they are listed in Table 1. Copper sulfide halides are still unknown. 

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