Selenium dithiocarbamates

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. 

Rubber. The mbber industry consumes finely ground metallic selenium and Selenac (selenium diethyl dithiocarbamate, R. T. Vanderbilt). Both are used with natural mbber and styrene—butadiene mbber (SBR) to increase the rate of vulcanization and improve the aging and mechanical properties of sulfudess and low sulfur stocks. Selenac is also used as an accelerator in butyl mbber and as an activator for other types of accelerators, eg, thiazoles (see Rubber chemicals). Selenium compounds are useflil as antioxidants (qv), uv stabilizers, (qv), bonding agents, carbon black activators, and polymerization additives. Selenac improves the adhesion of polyester fibers to mbber. 

In the course of the quest for new Fe(III) spin crossover compounds, systems related to N,N-disubstituted-dithiocarbamates have been explored. This section deals with oxygen and selenium derivatives of this parent ligand system, as displayed in Fig. 2. 

There have been conflicting interpretations of the EPR spectra of these selenium-containing complexes. For example, various X-band EPR spectra of Fe(III) diselenocarbamates recorded in chloroform solutions at 12 K tended to be broad and poorly resolved, except for a series of three resonances centred around g=2 [62]. They also appeared to be very similar to the spectra recorded for Mn(III)-doped Co(III) tris(dithiocarbamate) compounds [76] or Cu(II) di(diselenocarbamate) systems [77]. In another study of EPR spectra recorded for powdered Fe(III) thioselenocarbamates and diselenocarbamates at room temperature [69] broad, poorly resolved lines at g 4... 

Simultaneous speciation of inorganic selenium and tellurium in water samples by ICP-MS was performed after selective solid phase extraction (SPE), as discussed by Yu et al 9 Under acidic conditions Se (IV) and (TV) complexes with ammonium pyrrolidine dithiocarbamate were formed. The detection limits for Se and species in water samples were found to be 7ngl 1 and 3 ng 1 1, respectively. 

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. 

Disulfur dinitride, 6 126 Disulfur pentoxydiehloride, 3 124 analysis of, 3 126 Dithiocarbamates, of selenium(II) and tellurium(II), 4 91 Dithionic acid, salts of, 2 167 Dithionite ion, formation of, from sulfur dioxide by sodium hydride, 5 13... 

Cyanate condensation products of carbohydrazide, synthesis 11 Thiosemicarbazide, synthesis 12 Dithiocarbamates of selenium(II) and tellurium (II), synthesis 32 Aluminum phosphide, synthesis 7 Phosphorus(III) fluoride, synthesis 49... 

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. 

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