Dithiocarboxylates reactions with sulfur

The chemistry of the dithiocarboxylate complexes of nickel (II) has been investigated extensively. Interest in recent years has been mainly in the further investigation of the "sulfur-rich species, the perthiocarboxylates, and the unusual structures discovered in the dithiocarboxylate complexes (359). The violet complex formed by reaction of [Ni(C H5CS2)2] with sulfur or polysulfide, [Ni(CgHsCS2)2]2, origi-... 

Many dithiocarboxylate compounds of sulfur have been reported. Bis(thioacyl) disulfides 100, dimers of dithiocarboxylate ligands, are easily synthesized by oxidative dimerization of the corresponding dithiocarboxylic acids (Scheme 26) [151-154]. Their reactivities toward cycloaddition reactions and S-S bond cleavage have been investigated [155-157]. Bis(thioacyl) trisulfides 101 and tetrasulfides 102 are also prepared by treating the dithiocarboxylic acid with SCI2 and S2CI2, respectively [135]. 

On the one hand, the reaction of imidazolium-2-dithiocarboxylate 111 with bromine gives the corresponding cationic thioacylsulfenyl bromide 112 [173]. On the other hand, treatment of 111 with an equimolar amount of iodine gives the charge transfer complex 113. Two iodine atoms and a thiolate sulfur atom are arranged in almost a linear fashion in 113. Further treatment of 113 with an excess amount of iodine causes oxidative coupling, affording the dicationic disulfide 114 (Scheme 27). 

The reaction between [MoCl4(NCPr)2] and dithiocarboxylic acids is a general route to the preparation of eight-coordinate [Mo(S2CR)4] complexes.168 The crystal structure of [Mo(S2CPh)4] reveals these compounds to be isostructural with the dithiocarbamates, with a dodecahedral coordination around the molybdenum and average Mo—S distances of 2.475(1) and 2.543(1) A to the two different sulfur sites.170 Cyclic voltammetry has shown that in [Mo(acda)4] (Hacda = 2-aminocyclopent-l-ene-l-dithiocarboxylic acid) the Mo can be reversibly oxidized and reversibly reduced in one-electron processes.171... 

The preparation and properties of the dithiocarboxylic acids and their metal complexes have been reviewed several times.38"11 The formation of C—C bonds in the direct reaction of CS2 requires sufficiently nucleophilic carbon bases, directly or potentially accessible in the form of ambifunction-al phenoxides, organometalfic compounds, CH acidic compounds, enamines or ketimines. Carba-nions react with CS2 to give dithiocarboxylates. The preparation and purification of the adds is performed via their salts. Metal complexes are in general readily available. The bonding in these complexes is mostly of the type (27) but a bonding mode (28) is also found. Action of elemental sulfur upon heavy metal complexes of (29) aromatic dithiocarboxylic acids yields the perthio complexes (29) of these compounds. 

The zinc(II) complex 59 was obtained by the reaction of Zn(MeCN)4(BF4)2 with the corresponding sodium salt of dithiocarboxylic acid and subsequent recrystallization from pyridine (Fig. 15) [114]. The crystal structure was shown to be a distorted trigonal bipyramidal geometry with one sulfur atom from each of the dithiocarboxylato ligands occupying the axial sites. In the absence of donor molecules such as pyridine, one sulfur atom from the dithiocarboxylato ligand coordinates to another zinc center to form a dimer-like Zn(II) complex 60 in the crystalline state [115]. EXAFS study indicates that 60 retains the dimeric nature in the mesophase. 

The acyl formation reaction is suggested to proceed via initial attack at the carbyne carbon, but evidence is not conclusive. Reaction of the analogous Cp complexes with cyclohexene sulfide provides exclusively the dithiocarboxylate derivatives. Presumably the second sulfur addition is considerably more rapid than for the Tp complexes due to lowered steric crowding around the molybdenum... 

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