Silver complexes dithiocarbamates

Early crystallographic studies revealed the hexameric nature (R = Et, E r) (328,329) of silver(I) dithiocarbamate complexes in the solid state, although in solution they are believed to be in equilibrium with monomeric species (329). More recently, the diethyldithiocarbamate complex has been the subject of two further crystallographic studies (Fig. 241) (330,331). Delgado and Diez (329)... 

Tsunogai and Nozaki [6] analysed Pacific Oceans surface water by consecutive coprecipitations of polonium with calcium carbonate and bismuth oxychloride after addition of lead and bismuth carriers to acidified seawater samples. After concentration, polonium was spontaneously deposited onto silver planchets. Quantitative recoveries of polonium were assumed at the extraction steps and plating step. Shannon et al. [7], who analysed surface water from the Atlantic Ocean near the tip of South Africa, extracted polonium from acidified samples as the ammonium pyrrolidine dithiocarbamate complex into methyl isobutyl ketone. They also autoplated polonium onto silver counting disks. An average efficiency of 92% was assigned to their procedure after calibration with 210Po-210Pb tracer experiments. 

In 1959, it was reported that on mixing silver(I) A.A-dialkyl dithiocarbamates with the corresponding thiuram disulfide, dissolved in benzene or chloroform, the solution immediately turned blue. 8,539 ESR spectra of these solutions showed the formation of paramagnetic d9 Agn complexes. The reaction was explained by the equilibrium expressed in equation (37). 

A kinetic study of the oxidation of some hexameric silver(I) dialkyl dithiocarbamate complexes by thiuram disulfides to the silver(II) complexes has been reported.543 Although a 100-fold excess of the thiuram disulfide was used, the formation of the Ag111 complex reported earlier was not considered. 

The dithiocarbamate ion Pr2NCS2 forms a hexanuclear complex with a trigonal-antiprismatic array of silver ions. Similar anionic clusters are also formed with the related (NC)2C=CS2 ligand, e.g., [AgejLJ6- and [Aggl ]4-. Four-, five-, and six-... 

Many dithiocarbamate complexes of zinc, silver, cadmium or mercury improve emulsion stability, including bis(dibenzyldithiocarbamato)-zinc(II) or -cadmium(II) and silver(I) diethyldi-thiocarbamate. Cadmium salts, mixed with citric acid or tartaric acid and added to the emulsion, are reported to be effective. Mercury(II) complexes of ethylenediaminetetraacetic acid (EDTA) and related ligands and of solubilized thiols such as (4) can be used. Other coordination compounds reported include EDTA and related ligand complexes of Co and Mn, mixtures of Co salts with penicillamine (5) and macrocyclic complexes of Ag such as (6). The latter compounds may be used in diffusion transfer systems in which transferred maximum densities are stabilized. 

Silver(n) complexes, 839-850 amino adds, 846 aqua,844,850 biguanides, 849 2,2 -bipyridyl, 843 carboxylates, 844 cinchomeronic acid, 842 dipicolinic acid, 842 dithiocarbamates, 845 isodnchomcronic add, 842 isonicotinates, 840 lutidinic acid, 842 N-heterocyclic ligands, 839 nicotinates, 840 1,10-phenanthroline, 843 phthalocyanines, 848 picolinates, 840... 

The mechanism of 1 1 complex formation between palladium(II) and catechol and 4-methylcatechol has been studied in acidic media, and the rate of 1 1 (and 1 2) complex formation between silver(II) and several diols is an order of magnitude higher in basic solution than in acidic. The kinetics of formation and dissociation of the complex between cop-per(II) and cryptand (2,2,1) in aqueous DMSO have been measured and the dissociation rate constant, in particular, found to be strongly dependent upon water concentration. The kinetics of the formation of the zinc(II) and mercury(II) complexes of 2-methyl-2-(2-pyridyl)thiazolidine have been measured, as they have for the metal exchange reaction between Cu " and the nitrilotriacetate complexes of cobalt(II) and lead(II). Two pathways are observed for ligand transfer between Ni(II), Cu(II), Zn(II), Cd(II), Pb(II) and Hg(II) and their dithiocarbamate complexes in DMSO the first involves dissociation of the ligand from the complex followed by substitution at the metal ion, while the second involves direct electrophilic attack by the metal ion on the dithiocarbamate complex. As expected, the relative importance of the pathways depends on the stability of the complex and the lability and electrophilic character of the metal ion. 

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. 

Das and Sinha (1632) prepared a range of cationic arylazoimidazole (R aaiX) complexes [(R aaiX)Pd(S2CNR2)][C104] (R = Et R2 = C4HgO) (411), upon addition of dithiocarbamate salts to the dichoride in the presence of AgNOg and perchlorate. When the reaction is carried out in the absence of the silver salt. 

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