Selenium xanthates

There are single examples of sulfur and selenium xanthates with the remaining structures to be described in this section featuring tellurium as the central element. There are a significant number of binary xanthates and, in common with these, their organotellurium xanthates feature extensive supra-molecular association, usually, but not exclusively, via Te- S secondary bond interactions. A rare example of mixed-ligand 1,1-dithiolate structure is available where the odd dithiolate ligand is a dithiocarbamate. 

Organosulfur Adsorbates on Metal and Semiconductor Surfaces. Sulfur compounds (qv) and selenium compounds (qv) have a strong affinity for transition metal surfaces (206—211). The number of reported surface-active organosulfur compounds that form monolayers on gold includes di- -alkyl sulfide (212,213), di- -alkyl disulfides (108), thiophenols (214,215), mercaptopyridines (216), mercaptoanilines (217), thiophenes (217), cysteines (218,219), xanthates (220), thiocarbaminates (220), thiocarbamates (221), thioureas (222), mercaptoimidazoles (223—225), and alkaneselenoles (226) (Fig. 11). However, the most studied, and probably most understood, SAM is that of alkanethiolates on Au(lll) surfaces. 

Preparation of an ultrasonic slurry of the sample is occasionally used, as for example in the determination of cobalt, nickel and copper [200], selenium [39] and arsenic and antimony [40]. Extraction of leaves with a chloroform solution of xanthate completely extracted cadmium [41,103]. X-ray fluorescence spectroscopy is a nondestructive method of analysing plant materials if they can be converted into a suitable form for presentation to the instrument. 

Selenium(IV) oxychloride, 3 130 Selenium (II) xanthates, 4 91 Selenocyanates, metal, 2 186, 188 Shaking apparatus, for keeping... 

Selenium and tellurium dioxides react with alkali xanthates and dithiocarbamates to give xanthates and dithiocarbamates of selenium(IV) and tellurium(IV).1,2 Russell1 states that the product formed by sodium diethyldithio-carbamate and selenium dioxide sometimes appears as an equimolar mixture of selenium (II) dithiocarbamate and the corresponding bis(thiocarbamyl) disulfide, (R2NCS)2S2. The commercial selenium dithiocarbamates, prepared by the above-mentioned method, usually consist of such mixtures. The disulfide can, in most cases, be extracted from selenium (II) dithiocarbamate by means of cold benzene or chloroform. 

Xanthates and dithioearbamates of bivalent selenium and tellurium may be conveniently prepared3-5 by allowing sodium selenopentathionate or sodium telluropenta-thionate to react with alkali xanthates or dithiocar-bamates. The reactions are rapid and quantitative, and the products separate from the aqueous reaction mixtures in a high state of purity. 

A solution of 0.025 mol of sodium or potassium xanthate or dithiocarbamate in 100 ml. of water is added, with stirring, to 3.5 g. of sodium selenopentathionate (0.01 mol) or 4.0 g. of sodium telluropentathionate (0.01 mol) (.synthesis 31) dissolved in 100 ml. of water. The product immediately precipitates, and after being stirred for several minutes, it coagulates, leaving a clear liquid. It is filtered, washed with water and methanol, and dried in vacuo over sulfuric acid. Conditions for crystallization of some of these compounds are outlined in Table I. Selenium ethyl-xanthate, which is an oil, is extracted from the aqueous layer with ether. The ether extract so obtained is dried over anhydrous sodium sulfate, after which the ether is removed by distillation. 

The selenium derivatives of xanthates and dithiocar-bamates are greenish yellow the tellurium compounds are red In the solid state, the dithioearbamates are quite stable, while the xanthates decompose after a few days, liberating selenium or tellurium. The compounds are insoluble in and unaffected by water. The decomposition of the selenium compounds into selenium and disulfides is strongly catalyzed by xanthates and dithiocarbamate ions. The uncorrected melting points are summarized in Table I. 

Complexes of selenium with xanthate [17], 4-nitro-o-phenylenediamine (toluene) [18], and DDTC [19,20] have also been used in extractive separation of Se from many elements. 

Selenium(II) and tellurium(II) xanthates, dithiocarbamates, and related molecules have planar trapezoidal structures... 

MAJOR USES Used in the manufacture of rayon, carbon tetrachloride, floating agents, soil disinfectants, electronic vacuum tubes, optical glass, paint removers, varnishes, rubber cement used as a solvent in phosphorous, sulfur, selenium, bromine, iodine, fats, resins, rubbers, waxes, lacquers used as a chemical intermediate in cellophane, rubber compounds, fumigants, rare earth sulfides, xanthates. 

Thiones and related ligands Thiourea and related ligands Xanthates and dithiocarbamates Selenium and Tellurium Ligands Nitrogen Ligands... 

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