Thiuram disulfide metal complexes

The reaction of metallic copper with thiuram disulfides yields complexes of Cu I), which are polymeric in solution as well as in the solid state 121,122). In 123) the copper atoms are located at the corners of a slightly distorted tetrahedron with Cu—Cu distances ranging from 2.6—2.7 A. Each of the copper atoms is coordinated to three sulfur atoms in a nearly planar triangular arrangement and each sulfur atom coordinates one or two copper atoms. 

In dithiocarbamato complexes such an ambiguity can only occur when at least two dithiocarbamato ligands are bonded to a metal. In that case the question arises whether the compound is a bis (dithiocarbamato) or a thiuram disulfide complex. In these two types of complexes the oxidation number of the metal differs 2 units. 

Oxidation of these complexes with halogen results in the oxidation of the ligand, yielding a thiuram disulfide complex X2M(R4tds), leaving the oxidation state of the metal unchanged (99,100,161). 

The kinetics of oxidation of dithiocarbamate anions to thiuram disulfides in 30% aqueous acetone by [Mo(CN)g] , [W(CN)g] , and 10 other substitution-inert metal complexes have also been investigated 61). Dithiocarbamates decompose in acid solution and oxidations were consequently performed only on the anionic forms in the pH range 9-12, at which no change in rate constants was observed. The only exception was that of thiophenol, which, upon reacting with [Mo(CN)g] , showed that the reaction rate contribution due to oxidation of the PhSH form was less than 0.002% that of PhS . All of the dithiocarbamates obeyed a simple second-order rate law. 

Tetraalkylthiuram disulfides, R2NC(S)S-S(S)CNR2, are oxidized forms of the di-alkyldithiocarbamate ions R2NC(S)Sa Thiuram disulfides possess pronounced oxidative properties and can easily oxidize and stabilize polyvalent cations in high oxidation states (Ni(III), Cu(III), Ag(II), etc.) as well as coordinate these metal ions in the molecular form [18,19]. Therefore, it should always be kept in mind that complexation of polyvalent cations with dialkyldithiocarbamate anions can be accompanied by a redox equilibrium of the following type ... 

After the extraction procedure, the sample extracts should stand for 1 h to totally break up DTC metal complexes and thiuram disulfides, and to complete... 

The transformation may occur via initial coordination of the thiuram disulfide complex followed by later addition of the sulfur-sulfur bond to the metal center. A limitation would appear to be the ability of the metal center to undergo a two-electron oxidation. However, Stiefel and co-workers (184, 185) reported unusual examples, whereby addition of thiuram disulfides (R = Me, Et, i-Bu) to the rhenium(VII) complex, [Et4N][ReS4], results in the reduction of the metal center. Thus, addition of 1.5 equiv of thiuram disulfide affords dimeric rhenium(lV) complexes, [Re(p-S)(S2CNR2)2]2, while with 3 equiv rhenium(V)... 

Casey and Vecchio (186,187) developed the oxidative-addition of thiuram disulfides to metals in order to produce a one-step preparation of a wide range of transition metal dithiocarbamate complexes. In this way, [Ni(S2CNMe2)2] and [Zn(S2CNMe2)2] can be prepared in near quantitative yields. With copper, only the copper(II) species are seen, and this is in keeping with Akerstrom s (188) earlier observation that copper(I) species react instantaneously with thiuram disulfides to generate the analogous copper(II) complexes. 

Addition of thiuram disulfides to the niobium(IV) dimethyl complex [Cp2NbMe2] results in cleavage of the sulfur-sulfur bond and addition to the metal center (734). The nature of the final product is dependent on the alkyl substituents. With tetraethylthiuram disulfide, the molecular niobium(V) dithiocarbamate complex [Cp2NbMe2(ri -S2CNEt2)2] results, which is believed to contain a monodentate dithiocarbamate ligand. In contrast, tetramethylthiuram disulfide affords a 1 1 electrolyte, believed to be [Cp2NbMe(S2CN-... 

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