Other Thallium Compounds

Other Thallium Compounds.—A new, low-temperature form of TIS, i.e. a-TlS, has been revealed by radiocrystallographic examination of the Tl-S system.  

A redetermination of the crystal structure of TlTe shows that the Te sublattice had been incorrectly described previously. There are short Te—Te distances, comparable with covalent bond lengths.  

Anacker-Eickhoff, P. Jennische, and R. Hesse, Acta Chem. Scand. (A), 1975,29, 51. 

Ducourant, B. Bonnet, R. Fourcade, and G. Mascherpa, Bull. Soc. chim. France, 1975, 1471. 

Other Thallium Compounds.—Tl2 ions may be generated by flash photolysis of Tl111 solutions.626 Some of their redox reactions have been studied, and they give values of the standard reduction potentials for the reactions  

Further studies on the Tl2+ ion, similarly produced, including rate constants of a number of its reactions, have also been reported by Schwarz et a/.626 

The effect of Cl on the electronic spectrum of Tln produced by pulse radiolysis indicates that the species T1CT, T1C12, and TIClJ are all present. Rate constants for a number of reactions of these chloro-species have been reported.627 

The phase diagram of the Tl-S system reveals the existence of the following phases T12S, TL,S3, T1S, and T12S3.628 T14S3 forms monoclinic crystals in which one Tl111 atom is tetrahedrally co-ordinated by S atoms, and also interacts with 3 Tl+ ions.629 This interaction is thought to be electrostatic in nature. 

Other Thallium Compounds.— The electrical resistivities of K-Tl alloys over a wide range of compositions have been measured. The results suggest that a high degree of localized electron bonding occurs in the liquid alloy at a potassium mole fraction of 0.5. It is possible that the t)q)e of bonding is similar to that occurring in the solid intermetallic compound KTl, which crystallizes at lower temperatures.  

T1(VS), a homologue of lautite, CuAsS, may be synthesized by slowly heating TIS 4- V powder at 200 °C, under vacuum in a sealed silica tube.  

of HggTlg rises with pressure, with a slope of 3.44 °C kbar , giving a straight-line plot up to at least 35 kbar. No evidence was found for dis-proportionationation of the HggTlg in the pressure range studied.  

Thermodynamic functions have been calculated for the Hg-Tl system over the temperature range 257—583 K.  

Claire, R. Castanet, and M. Laffitte,/. Less-Common Metals, 1973, 31, 83. 

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ThaUous sulfate, thaUous nitrate, and thaUous and thaUic oxide are the main compounds produced in bulk quantities by Noah Chemical. Approximately 20 other thallium compounds are also available commercially from Noah Chemical, Cooper Chemical, and Alfa Products, Ventron Division, Thiokol Corporation, in research and production quantities. However, demand for thallium compounds is small and limited to such appHcations as synthetic or analytical reagents. 

Thallium carbonate (Tl COj) is used to make artificial diamonds (along with several other thallium compounds). 

The carboxylates of indium and thallium are obtained by dissolving the oxides in acid. Acetate and trifluoroacetate salts are used extensively as reagents in organic synthesis. Certain other thallium compounds have been used also. The trifluoroacetate, T1(02CCF3)3, will directly thallate aromatic compounds to give arylthal-lium species, for example, C6H5T1(02CCF3)2 (cf. aromatic mercuration, Section 15-15) and oxidize arenes to biaryls. 

Other thallium compounds of the type T1R2C1 (R = 2,3,4,6-C6F4H, 2,3,5,6-C6F4H, or 2,4,6-C6F3H2) can also be prepared by this method. Since they are more soluble in cold benzene, it is convenient to recrystallize them from a... 

Intermetallic compounds with gallium are used as semiconductors. Indium is used to coat other metals to protect against corrosion, especially in engine bearings it is also a constituent of low-metal alloys used in safety sprinklers. The toxicity of thallium compounds has limited the use of the metal, but it does find use as a constituent of high-endurance alloys for bearings. 

Production and Economic Aspects. Thallium is obtained commercially as a by-product in the roasting of zinc, copper, and lead ores. The thallium is collected in the flue dust in the form of oxide or sulfate with other by-product metals, eg, cadmium, indium, germanium, selenium, and tellurium. The thallium content of the flue dust is low and further enrichment steps are required. If the thallium compounds present are soluble, ie, as oxides or sulfates, direct leaching with water or dilute acid separates them from the other insoluble metals. Otherwise, the thallium compound is solubilized with oxidizing roasts, by sulfatization, or by treatment with alkaU. The thallium precipitates from these solutions as thaUium(I) chloride [7791 -12-0]. Electrolysis of the thaUium(I) sulfate [7446-18-6] solution affords thallium metal in high purity (5,6). The sulfate solution must be acidified with sulfuric acid to avoid cathodic separation of zinc and anodic deposition of thaUium(III) oxide [1314-32-5]. The metal deposited on the cathode is removed, kneaded into lumps, and dried. It is then compressed into blocks, melted under hydrogen, and cast into sticks. 

Uses. Tballium compounds have limited use in industrial appHcations. The use of thaHous sulfate in rodenticides and insecticides has been replaced by other compounds less harmful to animals (see Insect control technology Pesticides). Tb allium sulfide has been used in photoelectric cells (see Photovoltaic cells). A thallium bromide—thallium iodide mixture is used to transmit infrared radiation for signal systems. ThaHous oxide is used in the manufacture of glass (qv) that has a high coefficient of refraction. Tb allium formate—malonate aqueous solutions (Cletici s solution) have been used in mineral separations. Many thallium compounds have been used as reagents in organic synthesis in researchlaboratoti.es. 

The binary compounds of the Group 13 metals with the elements of Group 15 (N, P, As, Sb, Bi) are stmcturally less diverse than the chalcogenides just considered but they have achieved considerable technological application as III-V semiconductors isoelectronic with Si and Ge (cf. BN isoelectronic with C, p. 207). Their stmctures are summarized in Table 7.10 all adopt the cubic ZnS stmcture except the nitrides of Al, Ga and In which are probably more ionic (less covalent or metallic) than the others. Thallium does not form simple compounds... 

A variant of the Williamson ether synthesis uses thallium alkoxides. The higher reactivity of these can be of advantage in the synthesis of ethers from diols, triols and hydroxy carboxylic acids, as well as from secondary and tertiary alcohols on the other hand however thallium compounds are highly toxic. 

Emerald Green Copper compounds other than halides (when not moistened with HCI), thallium compounds. 

He knew that thallium compounds had no smell or taste and that the symptoms of poisoning could easily be mistaken for a variety of other ailments. But he wasn t quite as smart as he thought — Trepal neglected to get rid of the evidence. Police found a vial containing remnants of thallium nitrate in his home. George James Trepal now sits on death row while his lawyers attempt to cast doubt on the chemical evidence. And he s not the only thallium murderer to have received the death sentence. In Pennsylvania, Joann Curley awaits the same fate. 

As with indium, the literature contains a number of surveys of the general inorganic1 and organometallic chemistry of thallium,273 and the reviews of this element already cited are also concerned with the adducts of the halides and pseudohalides,5 and with other aspects of the coordination chemistry.6 A monograph by Lee provides a most useful treatment of the literature up to 1970.274 The application of thallium compounds in organic synthesis has been discussed.275 276... 

Thallium(I) ethoxide has been known for many years, and a series of related alkoxides can be prepared by methods which include Tl + ROH, TIOH + ROH and T120 + ROH.295 The ethoxide,296 and a number of other TIOR compounds,297 are tetrameric in solution, and an X-ray crystallographic study of (T10Me)4 shows that the structure is based on that of cubane,298 with no T1—T1 bonding interactions. The bonding in such molecules has been discussed.299 Phenoxide, and substituted phenoxides, can be prepared from PhOH + TlOH, while reaction... 

Thallium, atomic no. 81 This element is better known for its poisonous properties and links with almost undetected deaths and Agatha Christie -type murder mysteries.2 Thallium compounds are used in some countries as cheap insecticides, particularly for killing cockroaches. Intake of this element causes stomach pains, vomiting and nausea, painful soles and palms of hands, limb weakness, double vision, involuntary eye movements, hallucina tions, characteristic hair loss and white lines across the nails. The symptoms are often mis-diagnosed as other diseases. Treatment is with the chemical Prussian Blue... 

In contrast to the other elements of group 13, thallium is considered a soft acid in Pearson s soft/hard acid classification (see Hard Soft Acids and Bases).This makes the element and its derivatives unique, and leads to its potentially most outstanding feature the properties of thallium are a subtle blend of some of the most desirable properties of numerous other metals (e.g. heavy alkali metals, silver, mercury, and lead). Thallium compounds are stable in both oxidation states (-1-1 and -1-3). The trivalent cation is quite a strong oxidation reagent, since it is reduced to T1+ easily (standard redox potential E°(TP+ — Tl" ") = -1.25 V). The ease of this reduction is utilized in certain organic reactions. 

SAFETY PROFILE Human poison by unspecified route. Human systemic effects by ingestion nerve or sheath structural changes, extra-ocular muscle changes, sweating, and other effects. Flammable in the form of dust when exposed to heat or flame. Violent reaction with F2. When heated to decomposition it emits toxic fumes of Tl. Used as a rodenticide and fungicide, and in lenses and prisms, in high-density liquids, See also THALLIUM COMPOUNDS and POWDERED METALS. 

Now, these arylthallium compounds are useful, not in themselves, but as intermediates in the synthesis of a variety of other aromatic compounds. Thallium can be replaced by other atoms or groups which cannot themselves be introduced directly into the aromatic ring - or at least not with the same regiospecificity. In this way one can prepare phenols (ArOH, Sec. 24.5) and aryl iodides (Sec. 25.3). Direct iodination of most aromatic rings does not work very well, but the process of thallation followed by treatment with iodide ion gives aryl iodides in high yields. 

Of these three metal compounds, thallium compounds such as T1(N03)3 and T1(0C0CF3)3 have been widely utilized in organic synthesis. Both TP+ and Pb" + ions are isoelectronic and the former is a less powerful oxidant than the Pb(IV) ion. Oxidizing reactivities of Tl+ salts vary with the anion associated with the metal, the solvent and other factors. On treatment with T1(N03)3 [TTN], phenols generally undergo two-electron oxidation forming phenoxonium ions which will be attacked by a variety of nucleophiles. 

Information for other organometallic compounds is scarce. The corresponding methyl and ethyl derivatives of mercury, tin, and silicon were shown to undergo redistribution to yield random equilibrium mixtures of all possible metal alkyls. Rapid intermolecular exchange of the methyl groups in mixtures of trimethylaluminum-dimethylcadmium and dimethylzinc-dimethylcadmium was also demonstrated by NMR. The redistribution of mercury derivatives was found to be much slower. Further data are also available for thallium. - The four-center intermediate 154 was suggested to explain the observations [Eq. (6.149)] ... 

Ga, In and T1 are much less common elements, obtained in small amounts from sulfide minerals of other elements and used only in specialized applications. The metals are less reactive than aluminum Fig. 1 shows a Frost diagram in which the much larger negative slope (negative electrode potential see Topic E5) of A1 is apparent. Thallium compounds are extremely toxic but do not normally pose an environmental hazard because they are little used. 

There is also a lot of structural information for other thallium(III) compounds (e.g., organothallium compounds), which has been obtained from the spin-spin coupling pattern of their NMR spectra. However, no interatomic distances have been obtained in this way. 

Corresponding to the place in the Periodic Table, in Tl-compounds the metal occurs in oxidation states + I and + III. In contrast to the other Group IIIA elements, the monovalent form is more stable than the trivalent. The chemical and physical properties of metallic thallium and thallium compounds are similar to those of adjacent elements, mainly to lead (atomic number 82). 

EXPLOSION and FIRE CONCERNS Incompatibilities and reactivities vary depending upon the specific soluble thallium compound most thallium compounds are flammable in the form of dust when exposed to heat or flame reacts violently with other halogens at room temperature forms toxic compounds on contact with steam or moist air emits toxic fumes of T1 in a fire all extinguishing agents are allowed for firefighting purposes. 

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