Dithiolate ions

Ethylene and propylene episulfides polymerize in THE at 0-70°C in the presence of sodium naphthalene, and (importantly) the polymer contains no naphthalene residues. The reaction involves one-electron transfer followed by dimerization of the resulting radical to give a dithiolate ion. This ion then polymerizes an episulfide by anionic mechanism (Boileau et al. 1967 Scheme 7.14). 

Two alternative approaches to the synthesis of the partially unsaturated ring systems are depicted in Schemes 27 and 28. The addition of sulfide ion to the multiple bonds of (208) in the former is facilitated by the activating effect of the sulfinyl or sulfonyl moiety and reaction occurs rapidly, giving yields of 67-84% (79S47). The second approach illustrates the use of an unsaturated dithiolate ion (76JOC1484). The first dianion (209) is generated from electrochemically reduced carbon disulfide and reacts with 1,2-dibromoethane to give the fused compound (210). Hot base-catalyzed hydrolysis cleaves (210) to form a new dianion which, with 1,2-dibromoethane, affords the product. 

An alternative synthesis of 2,3-dihydro-1,4-dithiin employs an unsaturated dithiolate ion. Thus, c/5-l,2-ethylenedithiolate, generated from 1,2-dichloroethylene as shown, reacts with 1,2-dibromo-ethane to give the desired compound (Scheme 7) <91SM2093). 

Miscellaneous. Hynes and Moran have carried out kinetic studies on substitution reactions of Pt dithiolate complexes with CN and with several dithiolate ions. In the reactions with the bidentate ligands the mechanism is similar to that proposed for the corresponding reactions of the nickel and palladium complexes, and the order of reactivities is Ni Pd Pt = 10 10 1. Evidence for an unusual mechanism in some reactions of Pt complexes has been reported in the case of the process... 

The reaction of toluene-3,4-dithiol(3,4-dimercaptotoluene) and antimony trichloride ia acetone yields a yeUow soHd Sb2(tdt)2, where tdt is the toluene-3,4-dithiolate anionic ligand (51). With the disodium salt of maleonitnledithiol ((Z)-dimercapto-2-butenedinitrile), antimony trichloride gives the complex ion [Sb(mnt)2] , where mat is the maleonitnledithiolate anionic ligand. This complex has been isolated as a yeUow, crystalline, tetraethyl ammonium salt. The stmctures of these antimony dithiolate complexes have apparendy not been unambiguously determiaed. 

Active methylene compounds can add to 1,3-dithiolylium ions to give 2-substituted 1,2-dihydro-1,3-dithioles (206). Again, addition is often followed by oxidation (to 207). Alternatively, further addition can occur (to 208) (80AHC(27)151). In this reaction, (205) can be CH2(CN)2, CH2(COMe)2 or even MeCOMe. Somewhat similar reactions are shown by 1,3-diarylimidazolium ions. 

Quite a number of mixed sulfur-nitrogen macrocycles have been prepared, but these have largely been by the methods outlined in Chaps. 4 and 5 for the respective heteroatoms. An alternative method, involves the formation of a Schiff base, followed by reduction to the fully saturated system, if desired. An interesting example of the Schiff base formation is found in the reaction formulated in (6.12). Dialdehyde 14 is added to ethylenediamine in a solution containing ferrous ions. Although fully characterized, the yield for the reaction is not recorded. To avoid confusion with the original literature, we note the claim that the dialdehyde [14] was readily prepared in good yield by reaction of the disodium salt of 3-thiapentane-l, 5-diol . The latter must be the dithiol rather than the diol. 

Diphenylcarbazide as adsorption indicator, 358 as colorimetric reagent, 687 Diphenylthiocarbazone see Dithizone Direct reading emission spectrometer 775 Dispensers (liquid) 84 Displacement titrations 278 borate ion with a strong acid, 278 carbonate ion with a strong acid, 278 choice of indicators for, 279, 280 Dissociation (ionisation) constant 23, 31 calculations involving, 34 D. of for a complex ion, (v) 602 for an indicator, (s) 718 of polyprotic acids, 33 values for acids and bases in water, (T) 832 true or thermodynamic, 23 Distribution coefficient 162, 195 and per cent extraction, 165 Distribution ratio 162 Dithiol 693, 695, 697 Dithizone 171, 178... 

Answer Various sequences of C-S disconnections would no doubt all lead to good syntheses. Disconnect ion (4a) has the advantage of giving a symmetrical dithiol (5) and available (p T 53) chloroacetyIchloride. 

The chemistry of 1,2-dichalcogenolene ligands (Scheme 1) has been of increasing interest for the scientific community over the past 40 years, though 1,2-dithiolene systems, containing unsaturated 1,2-dithiolates, such as tdt2 (Scheme 2), and their reactivity towards several metal ions have been the subject of study since the mid-1930s by Clarcke and co-workers.1 3... 

Several studies suggest that LA and DHLA form complexes with metals (Mn2+, Cu2+, Zn2+, Cd2+, and Fe2+/Fe3+) [215-218]. However, in detailed study of the interaction of LA and DHLA with iron ions no formation of iron LA complexes was found [217]. As vicinal dithiol, DHLA must undoubtedly form metal complexes. However, the high prooxidant activity of DHLA makes these complexes, especially with transition metals, highly unstable. Indeed, it was found that the Fe2+-DHLA complex is formed only under anerobic conditions and it is rapidly converted into Fe3+ DHLA complex, which in turn decomposed into Fe2+ and LA [217]. Because of this, the Fe3+/DHLA system may initiate the formation of hydroxyl radicals in the presence of hydrogen peroxide through the Fenton reaction. Lodge et al. [218] proposed that the formation of Cu2+ DHLA complex suppressed LDL oxidation. However, these authors also found that this complex is unstable and may be prooxidative due to the intracomplex reduction of Cu2+ ion. 

The chloride ions of 143 are displaced by reaction with the dithiolene chelates, disodium maleonitrile dithiolate (Na2 mnt), benzene dithiolate (bdt)... 

Another factor that characterizes molybdenum and tungsten enzymes is that instead of using the metal itself, directly coordinated to amino acid side-chains of the protein, an unusual pterin cofactor, Moco, is involved in both molybdenum- and tungsten-containing enzymes. The cofactor (pyranopterin-dithiolate) coordinates the metal ion via a dithiolate side-chain (Figure 17.2). In eukaryotes, the pterin side-chain has a terminal phosphate group, whereas in prokaryotes, the cofactor (R in Figure 17.2) is often a dinucleotide. 

Zhang G, Zhang D, Yin S et al (2005) l,3-Dithiole-2-thione derivatives featuring an anthracene unit new selective chemodosimeters for Hg(II) ion. Chem Commun 2161-2163... 

Especially, PECH with triazine-3,5-dithiol substituent (5.) is interesting in their characteristic behavior towards metal ions and metal surface. 5,... 

The reaction of R —C=C—with the electrogenerated Sx ions provides a convenient method for the synthesis of substituted thiophenes (Eq. 30) [263]. Besides thiophenes, some dithiols, divinyl-sulfides and 2,4,6-tricarboxyethyl-l,3,5-trithiophenol were formed, the product distribution being governed by the nature of the substituents in the starting acetylenic substrate. 

The mixed-potential model demonstrated the importance of electrode potential in flotation systems. The mixed potential or rest potential of an electrode provides information to determine the identity of the reactions that take place at the mineral surface and the rates of these processes. One approach is to compare the measured rest potential with equilibrium potential for various processes derived from thermodynamic data. Allison et al. (1971,1972) considered that a necessary condition for the electrochemical formation of dithiolate at the mineral surface is that the measmed mixed potential arising from the reduction of oxygen and the oxidation of this collector at the surface must be anodic to the equilibrium potential for the thio ion/dithiolate couple. They correlated the rest potential of a range of sulphide minerals in different thio-collector solutions with the products extracted from the surface as shown in Table 1.2 and 1.3. It can be seen from these Tables that only those minerals exhibiting rest potential in excess of the thio ion/disulphide couple formed dithiolate as a major reaction product. Those minerals which had a rest potential below this value formed the metal collector compoimds, except covellite on which dixanthogen was formed even though the measured rest potential was below the reversible potential. Allison et al. (1972) attributed the behavior to the decomposition of cupric xanthate. 

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