Dithiocarbamic acid metal complexes

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Hill and co-workers studied the thermal decomposition of a large number of metal complexes of various alkyl derivatives of xanthic and dithiocarbamic acids. The complexes were studied by using TG. DSC. and other TA techniques. Compounds investigated included Nil IB alkyl xanthates (79), Cu(II) dithiocarbamate complexes (80), dihalotin (IV) bisdiethyldithio-carbamates (81), bisldiethyldithiocarbamatoi diphenyl tin (IV) (82), tetrakis-(diethyldithiocarbamatoi tin(lV) (83, 84), and bisidieihyldithiocarbamato) tin(IV) (85). 

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... 

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... 

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. 

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. 

Several researchers participated in the elucidation of the structure of dithiocarbamates (Van der Kerk et al., 1955 Chatt et al., 1956). Today it has been esteblished unequivocally that the salts of dithiocarbamic acid formed with metals are complex compounds (5) and that the compounds of ethylene-bisdithiocarbamate formed with bivalent metals even have a highly polymeric character (6). Little information pertinent to their structure is available, but a coordination structure such as (7) is conceivable (Vonk, 1975). 

Physical Properties of 1,3,4-Thiadiazoles. Ultraviolet spectra of some 2-benzylideneamino-5-phenyl-1,3,4-thiadiazoles have been reported. The n.m.r. spectral properties and conformational preferences of some open-chain and cyclic aromatic sulphides that contain 1,3,4-thiadiazole units, spectroscopic data of metal (Mn, Fe, Co, Ni, Cu, or Zn) chelates of iV-(5-phenyl-l,3,4-thiadiazol-2-yl)dithiocarbamic acids, conductometric and i.r. and Raman determinations on thirteen complexes of Zn, Cd, or Hg with 2-methyl-5-mercapto-1,3,4-thiadiazole, and thermogravimetry of some noble- and common-metal chelates of 5-amino-l,3,4-thiadiazole-2-thiol were also described, as well as the mass-spectral fragmentation of 2-phenyl-... 

Brooks, R.R., Hoashi, M., Wilson, S.M. and Zhang, R-Q. (1989) Extraction into methyl isobuthyl ketone of metal complexes with ammonium pyrrolidine dithiocarbamate formed in strongly acidic media. Anal. Chim. Acta, 217, 165-170... 

THE THERMAL PROPERTIES OF SOME METAL COMPLEXES OF DIETHYL-DITHIOCARBAMIC ACID. NEW VOLATILE METAL CHELATES. 

Metal complexes of dithioic acids, eg, dithiocarbamates, dithiophosphates, xanthates (MDRC, MDRP, MRX, respectively) (see AOs 21-24, Table 3), which are highly effective catalytic peroxide decomposers (PD-C) and excellent melt stabilizers, are generally effective photostabilizers (101,105,136,137,139,149). Their... 

With the exception of perchloric acid media, in which ttis(dithiocarbama-te)tellmiiun(lV) perchlorate species are formed (319), Te02 reacts with dithio-carbamate salts under acidic conditions to give the intensely colored homoleptic tetrakis(dithiocarbamate)teUurium(lV) complexes, [Te(S2CNR2)4]. The intense coloration results form Ugand-to-metal charge transfer (LMCT) bands in the visible region (293). 

It is not clear when dithiocarbamates were first prepared, but certainly they have been known for at least 150 years, since as early as 1850 Debus reported the synthesis of dithiocarbamic acids (1). The first synthesis of a transition metal dithiocarbamate complex is also unclear, however, in a seminal paper in 1907, Delepine (2) reported on the synthesis of a range of aliphatic dithiocarbamates and also the salts of di-iTo-butyldithiocarbamate with transition metals including chromium, molybdenum, iron, manganese, cobalt, nickel, copper, zinc, platinum, cadmium, mercury, silver, and gold. He also noted that while dithiocarbamate salts of the alkali and alkali earth elements were water soluble, those of the transition metals and also the p-block metals and lanthanides were precipitated from water, to give salts soluble in ether and chloroform, and even in some cases, in benzene and carbon disulfide. 

Here, the bridging dithiocarbamate ligands have resulted upon addition of a second metal center to terminal dithiocarbamates. Indeed, this is a relatively common feature and the sulfur atoms in a range of mononuclear dithiocarbamate complexes can bind to other Lewis acidic metal centers. 

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... 

Because of their polymeric forms, alkylenebis(dithiocarbamates) are insoluble in water and most organic solvents. Additionally, they form strong complexes with different metal ions No extraction and chromatographic procedure has been reported for the parent compound of this chemical class. These compounds decompose readily under acidic conditions, for example by contact with the fruit or plant juice generated during sample preparation. 

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