Thallium complexes cyanides

The reaction is a sensitive one, but is subject to a number of interferences. The solution must be free from large amounts of lead, thallium (I), copper, tin, arsenic, antimony, gold, silver, platinum, and palladium, and from elements in sufficient quantity to colour the solution, e.g. nickel. Metals giving insoluble iodides must be absent, or present in amounts not yielding a precipitate. Substances which liberate iodine from potassium iodide interfere, for example iron(III) the latter should be reduced with sulphurous acid and the excess of gas boiled off, or by a 30 per cent solution of hypophosphorous acid. Chloride ion reduces the intensity of the bismuth colour. Separation of bismuth from copper can be effected by extraction of the bismuth as dithizonate by treatment in ammoniacal potassium cyanide solution with a 0.1 per cent solution of dithizone in chloroform if lead is present, shaking of the chloroform solution of lead and bismuth dithizonates with a buffer solution of pH 3.4 results in the lead alone passing into the aqueous phase. The bismuth complex is soluble in a pentan-l-ol-ethyl acetate mixture, and this fact can be utilised for the determination in the presence of coloured ions, such as nickel, cobalt, chromium, and uranium. 

AuCN has a similar structure to AgCN and likewise dissolves in excess cyanide to form Au(CN)J this is important in the extraction of gold. It has been characterized as various salts (Tl, K, Bu4N, Cs) with Au-C 1.964A (Bu4N salt [91]). The thallium salt has short Au-Au (3.10A) and Au-Tl (3.50 A) interactions extended-Huckel calculations indicate the importance of relativistic effects in these covalent interactions. Isocyanides form stable complexes ... 

Mercuration of aromatic compounds can be accomplished with mercuric salts, most often Hg(OAc)2 ° to give ArHgOAc. This is ordinary electrophilic aromatic substitution and takes place by the arenium ion mechanism (p. 675). ° Aromatic compounds can also be converted to arylthallium bis(trifluoroacetates), ArTl(OOCCF3)2, by treatment with thallium(III) trifluoroacetate in trifluoroace-tic acid. ° These arylthallium compounds can be converted to phenols, aryl iodides or fluorides (12-28), aryl cyanides (12-31), aryl nitro compounds, or aryl esters (12-30). The mechanism of thallation appears to be complex, with electrophilic and electron-transfer mechanisms both taking place. 

Nitrosalicylhydrazide, 2778 Scandium 3-nitrobenzoate, 3816 Silver osmate, 0034 Thallium bromate, 0260 Thallium(I) methanediazoate, 0458 Thallium(I) 2- or 4-nitrophenoxide, 2187 Thallium acz-phenylnitromethanide, 2723 See also METAL AZIDES, METAL CYANIDES (AND CYANO COMPLEXES), /V-MKTAL DERIVATIVES... 

Alkali metal 1-methyl- and 1-phenyl-borinates are also available from bis(borinato)cobalt complexes (see below) on treatment with sodium or potassium cyanide in an aprotic solvent like acetonitrile. Cobalt cyanide precipitates and the alkali borinate remains in solution. After addition of thallium(I) chloride to some complexes, thallium 1-methyl- or 1-phenyl-borinate could be isolated as pale yellow solids, the only main group borinates isolated hitherto. They are insoluble in most organic solvents but readily soluble in pyridine and DMSO. The solids are stable on treatment with water and aqueous potassium hydride, but are decomposed by acids <78JOM(153)265). 

State. When both iron environments contain only iron(II), the resulting salt is not colored (Prussian White). The oxidation state localization in PB has been studied extensively. Structures, electrochemical behavior (electrodes batteries), and uses in medicine (treatment of Cs and of thallium poisoning) of Prussian Blue are mentioned in a review of cyanide complexes. In cobalt-iron Prussian Blue analogues, NaxCo3,Fe(CN)6-zH20 electronic and spin states are controlled by temperature and the ligand field strength around the Co + ions, which in turn is determined by the Co Fe ratio. ... 

Thallium(I) forms salts with cyanide (CN ), cyanamide (NCN ), azide (Ns"), cyanate (OCN ), isocyanate (CNO"), thiocyanate (SCN"), and selenocyanate (SeCN ) however, complexes with these hgands, hke the Tl -halide complexes, are very weak. In contrast, the neutral Tl Xs species are not well known, although the Tl -pseudohahde complexes are more or less stable. 

A detailed, multimethod study of hydrated Tl(III) cyanide species in aqueous solution reveals that Tl(III) forms very strong complexes with cyanide ions (even stronger than halide-Tl(III) interactions)." " Formation of a series of Tl(III) complexes T1(CN) n= -4t) has been established, and the solution structures and stability constants were reported. The mono- and dicyano complexes [Tl(CN)(OH2)5] and [Tl(CN)2(OH2)4] show six-coordinate thallium centers, whereas Tl(CN)3(OH2) and [T1(CN)4] have four-coordinate T1(III) ions. 

The main interfering metals in the copper determination are Fe, Bi, Mn, Ni, Co, Cr, Mo and U, which form coloured complexes. The selectivity of the method is considerably enhanced by the use of EDTA as a masking agent. In a tartrate or citrate medium at pH 8-9, Fe, Mn, Ni and Co are masked by EDTA, as are Cd, Pb, Zn, and In, which form colourless complexes with DDTC. Of the metals forming coloured compounds with DDTC, only Bi, Tl(III), and Cu are not masked. Thallium, when reduced to T1(I), does not interfere. Bismuth can be stripped from the organic extract, containing copper and bismuth diethyidithiocarbamates, with 5 M HCl. Copper diethyidithiocarbamate is decomposed by cyanide, whereas the bismuth complex remains unaffected. 

There are, however, some exceptions such as the cyanide complexes of the ions copper(I), silver(I), probably gold(I), and mercu-ry(II), where the extreme stability of the second complex, MX2, breaks the decreasing trend. The thallium(III) ion, which is isoelectronic with Au(I) and Hg(II), behaves in a similar way (97) (Table III). It is certainly not a coincidence that diorganothallium(III) compounds containing the linear C-Tl-C group are also extremely stable (15, 26) for example, the T1(CH3)2 ion is stable in aqueous solution (148). 

Fig. 6. Distribution of thallium(III) among the various T1(CN) C1 ,complexes as a function of the total cyanide concentration (mM) in acidic aqueous solution (charges omitted). [Tl(III)]t t = 50 mM, C1 ),ot = 50 mM. From Blixt and Glaser il08).

Blewitt JP (1946) Radiation losses in the induction electron accelerator. Phys Rev 69, 87-95 Blixt J, Glaser J, Mink J, Persson I, Persson P, Sandstroem M (1995) Structure of thallium(III) chloride, bromide, and cyanide complexes in aqueous solution. J Am Chem Soc 117 5089-5104 Blonski S, Garofalini SH (1993) Molecular dynamics simulation of -alumina and y-alumina surfaces. Surf Sci 295 263-274... 

Similar observations on the oxidation of the thallium atom or on the reduction of T1+ have been made by pulse radiolysis. They are in agreement, as for silver, with the value determined from the electrode potential and the sublimation energy of the bulk metal into atoms, i.e. °(T1 /T1 ) = —1.9 Vnhe-Silver ions complexed by cyanide, ammonia, or EDTA, Ag L, are not reduced by the radical (CH3)2C OH, even under basic conditions, and the redox potential of these complexed forms must be more negative than —2.1 According... 

Thallium(Il) complexes, 171 Thallium(III) complexes, 171 amines, 172 ammines, 172 aqua, 172 bipyridyl, 172 bromates, 173 bromides, 174 carboxylates, 173 chlorates, 173 chlorides, 174 cyanides, 171 dichlorophosphates, 173 ethers, 173... 

If solvent extraction is carried out in the presence of cyanide, the zinc group of metals (Zn, Cd, Hg) is complexed and they will not extract. Addition of citrate complexes the elements of the ammonia group (Fe, Al, etc.) so that their hydroxides will not precipitate. The precipitation of the alkaline earth phosphates can be prevented by the addition of hexametaphosphate (Jl). Under these conditions, Bi(III), TI(I), and Sn(II) interfere in alkaline solution. The bismuth can be removed by preextraction at pH 3. Alternatively, if a positive lead test is found, bismuth could be ruled out or confirmed by back-extracting at pH 3. If bismuth is present, it will remain in the organic layer while lead will go into the aqueous phase. Extraction of thallium can be prevented by extracting the lead at pH 6.0-6.4 with chloroform. Or the thallium can be back-extracted at this pH this requires much closer control of the pH. The oxidation of dithizone by air is catalyzed by the presence of significant amounts of manganese (II). 

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