Lead dithiocarbamate complexes

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. 

The EPR spectrum of a spin-equilibrium complex can be used to establish a lower limit to the spin state lifetimes of the order of 10 10 second. In an important paper in 1976, Hall and Hendrickson reported observation of EPR signals for both the high-spin and the low-spin isomers of iron(III) dithiocarbamate complexes at 4 12 K as powders, glasses, and doped solids (71). This resolved the question whether these complexes possess distinct high-spin and low-spin states. It also sets a lower limit on their interconversion lifetimes. Similarly, the observation of signals for both the high-spin and low-spin states of [Co(terpy)22+] (97) leads to the same conclusions about this complex. In both cases the interconversion rates in solution have proved too fast to measure, with lifetimes of less than 10-9 second indicated. The solution measurements were undertaken, of course, at room temperature and the EPR measurements at close to 4 K. Significant differences in the rates of solid and solutions at room temperature are still possible. 

Zinc complexes are important as additives for rubber polymers. Dithiocarbamate complexes are most commonly used here, but bis(8-hydroxyquinolinato)zinc inhibits the thermal decomposition of poly[(trifluoroethoxy)(octafluoropentoxy)phosphazene]. The zinc is thought to complex residual P—OH groups in the polymer chain, which would otherwise lead to rearrangement and chain scission.126... 

Atsuya I, Itoh K, Ariu K. 1991. Preconcentration by coprecipitation of lead and selenium with nickel-pyrrolidine dithiocarbamate complex and their simultaneous determination by internal standard atomic absorption spectrometry with the solid sampling technique. Pure Appl Chem 63(9) 1221-1226. 

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. 

The homoleptic dithiocarbamate complexes of both Sn and Pb have been investigated recently as possible single source precursors for the deposition of metal sulfide materials (98, 105, 106) and dithiocarbamates have also been used for the extraction of lead from environmental samples (107). 

Although nonhomoleptic complexes of Sn have been extensively studied because of their considerable structural diversity and potential applications, for example, in chemotherapy, those of lead are rare. The complex [Pb(phen)(S2C-NEt2)2] (phen = 1,10-phenanthroline) is one of only a few examples of a nonhomoleptic lead(II) dithiocarbamate complex (108). The geometry at Pb (Fig. 7) is best considered as distorted trigonal bipyramidal, with the bridging S atoms occupying axial positions. 

Reactions of tris(dithiocarbamate) complexes with iodine have been studied in some detail and lead to a range of products, being dependent on the conditions utihzed and substituents on the dithiocarbamate ligands, as discussed more fully in Section IV.E.l.b. 

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