Dithiocarbamates, of selenium

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... 

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. 

The major changes in the format and contents of this volume have been necessitated by economic considerations. Sulphur-containing heteroaromatic compounds which previously were included in these Reports and in the Reports on Aromatic and Heteroaromatic Chemistry are now covered in detail only in the new Reports, Heterocyclic Chemistry . The literature on these compounds has been reviewed up to March 1978 in Volume 5 of this series and thereafter in Volume 1 of the new series. Highlights of the literature of these compounds are given as Chapter 6 of this volume. The organization of the remainder of this volume is essentially the same as that of Volume 5 except that the section on the ylides and carbanionic compounds of selenium and tellurium has been considerably extended and the coverage of Chapter 3, Part III has been extended to include dithiocarbamates, xanthates, and trithiocarbonates. 

There are no oxygen dithiocarbamate complexes and, although dithiocarba-mates do bond to sulfur, forming thiurams, these are considered as a separate class of compound and fall outside the scope of this chapter. While the dithiocarbamate complexes of selenium remain relatively few in number, those of tellurium have been studied more extensively, with particular attention being paid to the different possible coordination numbers and geometries displayed by the metal atom. 

Reaction of selenium(IV) dioxide with sodium dithiocarbamate salts yields the homoleptic selenium(II) bis(dithiocarbamate) complexes [Se(S2CNR2)2] (293-297). No selenium(IV) dithiocarbamate complexes appear to have been authenticated and dithiocarbamate ligands have been successfully employed as a method of separating selenites from selenates (298), as well as from other metal... 

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. 

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. 

S- and Se-Donor Ligands. The majority of the reported work once more relates to dithiocarbamate and related ligands, and some novel selenium work has appeared. 

Atsuya I, Itoh K, Ariu K. 1991. Preconcentration by coprecipitation of lead and selenium with nickel-pyrrolidine dithiocarbamate complex and their simultaneous determination by internal standard atomic absorption spectrometry with the solid sampling technique. Pure Appl Chem 63(9) 1221-1226. 

Sulphur and Selenium Derivatives of Bivalent Germanium, Tin, and Lead. Tin(ii) bis(diethyldithiocarbamate) and bis(methyldithiocarbonate) have been prepared from tin(ii) chloride and the respective potassium salt. Dialkyldithiocarbamates have also been obtained using the ammonium salts. T.g.a. data suggest that the thermal decomposition of the dithiocarbamates proceeds via stepwise loss of complete ligands. ... 

---