Cobalt complexes disulfides

Table 6 Structures Cobalt-Carbon Disulfide Complexes ...

SO2C2H4, Acetic acid, 2-mercapto-cobalt complex, 21 21 SSnCisH32, Tin, (benzenethiolato)tributyl-, 25 114 S2, Disulfide... 

Cobalt complexes, 635-882 ADP, 760 amides, 682 arsenates, 774 arsenic ligands, 767-775 ATP, 760 bipyridyl, 691 bis(dithiolates), 876 carboxylates, 790 cyanates, 679 cyanides reduction, 646 disulfides, 829... 

Cobalt complexes of polymeric phthalocyanines have been employed in aqueous alkaline solution as heterogenous catalysts in the oxidation of thiols to disulfides (MEROX, mercaptan oxidation process in the petroleum industry, Eq. 6-12, see Sections 5.2 and 5.4, Experiments 5-11 and 5-12). The catalytic activities of the polymer 31 (M = Co(II)) are higher than those of dissolved low molecular weight phthalocyanines, and both complexes exhibit better activities on charcoal than on Si02 as carrier. This is the result of better electrical contact between different reaction centers, which facilitates a multi-electron process in the oxidation of R-S to R-S-S-R and reduction of O2 to H2O [95]. Another advantage of the heterogeneous catalysts in comparison to the dissolved low molecular weight phthalocyanines is their easy re-use. 

Liganded cobalt complexes react with carbon disulfide by addition across one of the C=S bonds to give relatively stable complexes 10. The same complex reacts with carbonyl sulfide to give a liganded carbonyl complex 11 andMesPS. In the reaction of carbon sulfose-lenide at -20 °C the adduct 12 as well as the thiocarbonyl complex 13 are formed, indicating that carbon sulfoselenide can be used for the synthesis of thiocarbonyl compounds. 

When the Claus reaction is carried out in aqueous solution, the chemistry is complex and involves polythionic acid intermediates (105,211). A modification of the Claus process (by Shell) uses hydrogen or a mixture of hydrogen and carbon monoxide to reduce sulfur dioxide, carbonyl sulfide, carbon disulfide, and sulfur mixtures that occur in Claus process off-gases to hydrogen sulfide over a cobalt molybdate catalyst at ca 300°C (230). 

The two major methods used for the synthesis of cobalt(III) dithiocar-bamates are (a) treatment of a cobaltous salt with aqueous NaR2dtc in the presence of air, or (b) oxidation of a cobalt(II) salt with tetraalkyl-dithiuram disulfides. In recent years, a complex with morpholine-4-carbodithioate (Mdtc), [CofMdtcla], has been prepared and character-... 

Examples in organometallic systems are known. Reaction of thiuram disulfides, (R2NCS2)2, with Co(Cp)(CO)2 produces dithiocarbamato pseudo-octahedral cobalt(III) complexes Co(Cp)(dtc)2 with one chelated and one monodentate dtc, also accessible via Co(Cp)I(dtc).1050 Fluxional behavior, including monodentate chelate exchange, was observed for some complexes in temperature-dependent NMR studies. The Co(Cp)I(dtc) complex was defined in a crystal structure. 

In abroad sense, the model developed for the cobaloxime(II)-catalyzed reactions seems to be valid also for the autoxidation of the alkyl mercaptan to disulfides in the presence of cobalt(II) phthalocyanine tetra-sodium sulfonate in reverse micelles (142). It was assumed that the rate-determining electron transfer within the catalyst-substrate-dioxygen complex leads to the formation of the final products via the RS and O - radicals. The yield of the disulfide product was higher in water-oil microemulsions prepared from a cationic surfactant than in the presence of an anionic surfactant. This difference is probably due to the stabilization of the monomeric form of the catalyst in the former environment. 

Catalysts based on molybdenum disulfide, M0S2, and cobalt or nickel as promoters are used for the hydrodesulfurization (HDS) and hydrodenitrogenadon (HDN) of heavy oil fractions [48,49]. The catalyst, containing at least five elements (Mo, S, Co or Ni, as well as O and A1 or Si of the support), is rather complex and represents a real challenge for the spectroscopist. Nevertheless, owing largely to research in the last twenty years, the sulfided C0-M0/AI2O3 system is one of the few industrial catalysts for which we know the structure in almost atomic detail [49, 50],... 

The formation of complexes of l,2,3,4-thiatriazole-5-thiol has been well described in CHEC-II(1996) 1,2,3,4-thiatriazole-5-thiol can form complexes with various metals such as palladium, nickel, platinum, cobalt, zinc, etc. <1996CHEC-II(4)691>. These complexes can be prepared either by cycloaddition reactions of carbon disulfide with metal complexes of azide anion (Equation 20) or directly from the sodium salt of l,2,3,4-thiatriazole-5-thiol with metal salts. For instance, the palladium-thiatriazole complex 179 can be obtained as shown in Equation (20) or it may be formed from palladium(ll) nitrate, triphenylphosphine, and sodium thiatriazolate-5-thiolate. It should be noted that complexes of azide ion react with carbon disulfide much faster than sodium azide itself. 

The role of Coball-dioxygen complexes in autooxidations other than phenol oxidation is less certain, and ostensibly similar reactions appear to follow radically different pathways. Thus, in the oxidation of thiols to disulfide catalyzed by Co11 species catalysis by the phthalocyanine complex [Con(TSPc)]4 apparently proceeds via a Co1 intermediate and without participation of Co—02 species,680 whereas catalysis by [CoH(TPP)] appears to involve initial formation of an >/ cobalt-dioxygen complex from which Of is displaced by thiolate.681 Several reviews giving extensive coverage to oxidations catalyzed by cobalt(II) complexes are available.649,650,682 683... 

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