Metal tris dithiocarbamate

The most numerous and most thoroughly studied metal hydrosulfide complexes are those of molybdenum, and they have often been used as models for HDS-related reactions and intermediates (for a comprehensive account, see ref. 3). Their syntheses, however, do not involve direct reaction with HjS very often. For instance, an interesting complex containing a hydrosulfido ligand on a Mo(IV) center in a sulfur-only environment is the tris(dithiocarbamate) derivative (a), which resembles some of... 

Intra- and Intermolecular Rearrangements. Pignolet and cO-workers (44) described a variety of intramolecular rearrangements of the tris (dithiocarbamates) and suggested that with iron (II) as the metal ion the process involves a trigonal prismatic intermediate. With the nickel (IV) complex, only a broad PMR spectrum was observed with no resolution... 

Table 30 Comparison of the activation enthalpies for metal-centred inversion by the Bailor trigonal-twist mechanism with the bite (a), twist ( ), and pitch (y>) angles ofNN-disubstituted tris(dithiocarbamate) metal complexes...

The ambient temperature solution NMR spectra of the tris(dithiocarbamate) complexes, including those of Al (see above), show the complexes to be fluxional on the NMR chemical shift time scale. The stereodynamics can be quite complex with several different processes possible, namely, (1) a metal-centered rearrangement of the ligand polyhedron, (2) reversible ligand dissociation, (3) restricted rotation about the single N—C bonds of (bulky) N substituents. 

The sulfur atoms in tris(dithiocarbamate) complexes can bind to Lewis acidic metal centers. For example, varying amounts of copper(I) iodide can be added to [Cr(S2CNR2)3] in acetonitrile to yield complexes in which sulfur atoms bridge... 

Tseng et al. [69] determined 60cobalt in seawater by successive extractions with tris(pyrrolidine dithiocarbamate) bismuth (III) and ammonium pyrrolidine dithiocarbamate and back-extraction with bismuth (III). Filtered seawater adjusted to pH 1.0-1.5 was extracted with chloroform and 0.01 M tris(pyrrolidine dithiocarbamate) bismuth (III) to remove certain metallic contaminants. The aqueous residue was adjusted to pH 4.5 and re-extracted with chloroform and 2% ammonium pyrrolidine thiocarbamate, to remove cobalt. Back-extraction with bismuth (III) solution removed further trace elements. The organic phase was dried under infrared and counted in a ger-manium/lithium detector coupled to a 4096 channel pulse height analyser. Indicated recovery was 96%, and the analysis time excluding counting was 50-min per sample. 

Several corrosion inhibitors such as polyamide, polyamine, dithiocarbamate, thiophosphate ester, organic acid, sulfide, and selenide types have all been tried in methanol without significant success [3.5]. Similarly, nonmetallic coatings of metals to effectively prevent corrosion have not been developed to date. One application where coatings have proven effective is in prevention of anodic dissociation of fuel pumps immersed in methanol. Since methanol is many times more conductive than gasoline, components such as fuel pumps and electrical fuel level gauges can cause induced currents that in turn remove metal from these... 

Tris(pyrrolidine dithiocarbamato-)—cobalt(III) chelate, the precipitate formed by adding ammonium pyrrolidine dithiocarbamate to cobalt(II) solutions, has been found to be a good matrix for preconcentrating lead and several other metals by co-precipitation. Concentration factors of 40 to 400 are available by the method. The analyte is co-precipitated on the Co-APDC from a litre of sample. The precipitate is filtered on a fine porosity glass sinter and redissolved in a small volume of 6 M nitric acid. The solution is then used for atomic absorption analysis. 

Despite the ambiguity regarding the assignment of formal oxidation states to metal and ligand in many dithiolate complexes, the structure and properties of the benzyltriphenylphosphonium salt of tris(l,l-dicarboethoxyethylene-2,2-dithiolato)ferrate [BzPh3P]2[Fe(DED)3] (DED = structure 139) are considered486 to be best described in terms of an Fe,v complex. The structure is close in important details to that of the dithiocarbamate complex described above.485... 

Dithiocarbamic acid itself and its alkali metal salts are unstable towards hydrolysis but metal chelates are known and a structure of [Co(S,CNH2)3] is available (Table 96). This complex is probably unstable towards hydrolysis giving [Co(S2CO)3]3. Salts of dithiocarbamates derived from primary amines are also unstable under alkaline conditions, although N(3)-substituted dithiocar-bazic acid forms green tris(S,S) chelates (336).1133 The similar N(3)-unsubstituted acids form (N,S) chelates (337) which can be deprotonated when R = H with possible isomerization to the (S,S) dithiocarbimate chelate (339).1133 The (N,S) chelate (338) has been positively identified by a crystal structure of its 5-methyl ester, R = H (Table 96).1134... 

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