Metal dithiocarbamate complexes

Burba P. and Willmer P. G. (1987) Multielement-preconcentration for atomic spectroscopy by sorption of dithiocarbamate-metal complexes (e.g. HMDC) on cellulose collectors, Fresenius Z Anal Chem 329 539—545. 

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...

Dithiobenzoic acid metal complexes, 2, 646 colours, 2, 646 Dithiobiuret metal complexes, 2, 640 Dithiocarbamates chelating resins mineral processing, 6,826 Dithiocarbamic acid metal complexes, 2,585 amine exchange, 1,428 photographic emulsions, 6,98 nickel poisoning, 6,768 tellurium(Il) complexes photothermography, 6,121 Dithiocarbazic acid metal complexes, 2,803 Dithiocarbimic acid metal complexes, 2,588 Dithiocarbimic acid, cyano-metal complexes, 2,808 Dithiocarboxylic acids metal complexes, 2,646 Dithiodiacetic acid metal complexes, 2, 806 Dithiodiketones... 

Metal complexes of ligands containing a sulfur donor in conjunction with nitrogen, oxygen or a second sulfur have been reviewed in the past [11-13]. For example, reviews of the coordination compounds of dithiophosphates [14], dithiocarbamates [15, 16], dithiolates [17], dithiodiketonates [18], and xanthates [16] have appeared. The analytical aspects [19] and the spectral and structural information of transition metal complexes of thiosemicarbazones [20, 21] have been reviewed previously. Recent developments in the structural nature of metal complexes of 2-heterocyclic thiosemicarbazones and S-alkyldithiocarbazates, depicted below, are correlated to their biological activities. 

Keywords Controlled Polymerization Living Radical Polymerization Iniferter Chain-End Structure Molecular Weight Control Block Copolymer Dithiocarbamate Disulfide Nitroxide Transition Metal Complex... 

Samples of metal complexes isolated from the final solutions were subjected to microanalysis (for carbon, hydrogen, oxygen, and sulfur). Metals were determined colorimetrically by the following methods— copper as the complex formed with sodium diethyl dithiocarbamate (6) cobalt as the nitroso-R salt complex (7) nickel as the dimethylglyoxime complex (4). 

The synthesis and metal complexes of the pyrrole dithiocarbamate ligand were reported by Kellner et al. (386). At a later date two independent studies dealt with the coordination chemistry of this ligand (26, 211). An outstanding feature of this molecule is the pyrrole ring, which, by preserving aromaticity makes the contribution of resonance form B (Fig. 4) insignificant (26) and creates a dominant -accepting character at the sulfur atoms (26). 

Ammonium dithiocarbamates can be prepared through reaction (11). With HC1 or H2S04 at lower temperatures the free acids are formed. Only one transition metal complex (37) is known, with a pseudo-octahedral coordination of Ni four sulfur atoms of the dithiocarbamate in the equatorial plane and two pyridine solvent molecules at the apical positions. Sulfides can be eliminated from monosubstituted dithiocarbamates to give isothiocyanates.53... 

Unsubstituted and mono substituted ammonium dithiocarbamates react with sodium chloro-acetate to produce different rhodanines, from which numerous metal complexes have been made.55... 

The ligand field strength of the ligands is between that of the dithiocarbamates and water.49 IR studies show characteristic bands near 1250, 1100, 1020 and 550 cm-1.93 The contribution of the resonance form (85) in transition metal complexes is less than that of the analogous structure in the dithiocarbamates.60 The electron density on the metal is not very high, which accounts for the fact that abnormal high oxidation states are exceptional and a strong interaction of bases with the square planar nickel (and some other metal) xanthates is found.94... 

The metal complexes of diethyl dithiophosphate were first investigated in 1931,134 when it was shown that the transition metal complexes [M((EtO)2PS2 ] (n = 2 or 3) were similar to those of xanthates and dialkyl dithiocarbamates, containing a four-membered XSMS (X = C or P) ring. A... 

Shih and Carr [277,278] showed that metal complexes of bis(/ -butyl-2-naphthyl-methyldithiocarbamate) are thermodynamically stable and chemically inert and that the nickel(II), iron(III), copper(II) and mercury (II) complexes of this dithiocarbamate can be separated by high performance liquid chromatography and detected with a variable wavelength detector. 

Carbon-based sorbents are relatively new materials for the analysis of noble metal samples of different origin [78-84]. The separation and enrichment of palladium from water, fly ash, and road dust samples on oxidized carbon nanotubes (preconcentration factor of 165) [83] palladium from road dust samples on dithiocarbamate-coated fullerene Cso (sorption efficiency of 99.2 %) [78], and rhodium on multiwalled carbon nanotubes modified with polyacrylonitrile (preconcentration factor of 120) [80] are examples of the application of various carbon-based sorbents for extraction of noble metals from environmental samples. Sorption of Au(III) and Pd(ll) on hybrid material of multiwalled carbon nanotubes grafted with polypropylene amine dendrimers prior to their determination in food and environmental samples has recently been described [84]. Recent application of ion-imprinted polymers using various chelate complexes for SPE of noble metals such as Pt [85] and Pd [86] from environmental samples can be mentioned. Hydrophobic noble metal complexes undergo separation by extraction under cloud point extraction systems, for example, extraction of Pt, Pd, and Au with N, A-dihexyl-A -benzylthiourea-Triton X-114 from sea water and dust samples [87]. 

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. 

Of course the reduction process also results in exclusion of small dopant anions from the polymer backbone. The dopants can be chosen so that the release process has the desired effect on the chemical composition of the immediate environment. For example. Miller described the triggered release of glutamate [59] and salicylate [60] amongst other compounds. In our own laboratories we have demonstrated the ability to release quinones [61] and metal complexing agents, dithiocarbamates (VII shown below) [62]. 

Dithiocarbamic acids, R2NC(S)SH, are rather unstable and seldom isolated or used as such. Usually their alkali metal or (substituted) ammonium salts are prepared for further use as starting materials in the synthesis of various metal complexes or organometallic derivatives. The most common is the reaction of primary or secondary amines with carbon disulfide in alkaline medium. 

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