Thallium isolation

Gr. thallos, a green shoot or twig) Thallium was discovered spectroscopically in 1861 by Crookes. The element was named after the beautiful green spectral line, which identified the element. The metal was isolated both by Crookes and Lamy in 1862 about the same time. 

There is no evidence for the existence of thallic hydroxide addition of hydroxide to an aqueous solution of a T1(III) salt gives TI2O2 instead. ThaHous hydroxide can be isolated as yellow needles by the hydrolysis of thaHous ethoxide [20398-06-5] which is conveniendy prepared as a heavy oH by the oxygen oxidation of thallium metal in ethanol vapor. ThaHous hydroxide darkens at room temperature and decomposes to TI2O and H2O on warming. 

Several derivatives of indolo[3,2-fi]carbazole, such as the system 185, have been claimed to arise from the reaction of suitably substituted simple indoles on treatment with thallium triacetate in acetic acid. A compound having the purported structure of 185 was thus isolated when 2,3-dimethylindole was used as the substrate [78UC(B)422]. Many years later, it was demonstrated that this product is in fact a derivative of indolo[2,3-c]carbazole (cf. Section VI) (99T12595). 

The synthesis and characterization of the monomeric amidinato-indium(I) and thallium(I) complexes [Bu C(NAr)2]M[But(NAr(NHAr)] (M = In, Tl Ar = 2,6-Pr2CgH3) have been reported. Both compounds were isolated as pale yellow crystals in 72-74% yield. These complexes, in which the metal center is chelated by the amidinate ligand in an N, j -arene-fashion (Scheme 33), can be considered as isomers of four-membered Group 13 metal(I) carbene analogs. Theoretical studies have compared the relative energies of both isomeric forms of a model compound, In[HC(NPh)2]. ... 

The reason for the effectiveness of triphenylphosphine is at present uncertain, although its eventual isolation as triphenylphosphine oxide indicates that it may well function as a scavenger for the thallium(III) released in the metal-metal exchange reaction. 

Monoalkylthallium(III) compounds are unstable (73, 79), and very few examples of this class have been isolated. A number of alkylthallium diacetates have been obtained either from oxythallation of olefins with thallium-(III) acetate (see below) or from exchange reactions such as that shown in Eq. (11) (74, 75). Only four alkylthallium dihalides have been isolated so far, namely a neopentylthallium dihalide (60) [Eq. (12)] and the isomeric 2-, 3-, and 4-pyridiomethylthallium dichlorides (20) [Eq. (13)]. Monoaryl-and monovinylthallium(III) derivatives are considerably more stable than... 

Yields in the above reactions can often be improved by the addition of 1 mole of triphenylphosphine directly to the trifluoroacetic acid solution of the reactants immediately before final work-up. It would appear that the triphenylphosphine functions as a scavenger for TTFA released in the metal-metal exchange reaction, thus protecting the final phenol from further electrophilic thallation and/or oxidation. Validation of the metal-metal exchange mechanism was obtained indirectly by isolation and characterization of an ArTlX2/LTTFA complex directly from the reaction mixture. NMR analysis revealed that this complex still possessed an intact aryl-thallium bond, indicating that it was probably the precursor to the transmetallation products, an aryllead tristrifluoroacetate and TTFA. 

Monoalkylthallium(III) compounds can be prepared easily and rapidly by treatment of olefins with thallium(III) salts, i.e., oxythallation (66). In marked contrast to the analogous oxymercuration reaction (66), however, where treatment of olefins with mercury(II) salts results in formation of stable organomercurials, the monoalkylthallium(III) derivatives obtained from oxythallation are in the vast majority of cases spontaneously unstable, and cannot be isolated under the reaction conditions employed. Oxythallation adducts have been isolated on a number of occasions (61, 71,104,128), but the predominant reaction pathway which has been observed in oxythallation reactions is initial formation of an alkylthallium(III) derivative and subsequent rapid decomposition of this intermediate to give products derived by oxidation of the organic substrate and simultaneous reduction of the thallium from thallium(III) to thallium(I). The ease and rapidity with which these reactions occur have stimulated interest not only in the preparation and properties of monoalkylthallium(III) derivatives, but in the mechanism and stereochemistry of oxythallation, and in the development of specific synthetic organic transformations based on oxidation of unsaturated systems by thallium(III) salts. 

Wiberg and Koch 167) also disagreed with Littler s results, and found that the major product (75%) obtained on treatment of cyclohexanone with aqueous thallium(III) perchlorate was cyclopentanecarboxylic acid (XL). 2-Hydroxycyclohexanone was isolated in only 3 % yield unchanged starting material accounted for the remainder of the product. Wiberg and Koch were unable to detect any cyclohexane-1,2-dione in the product mixture, but did prove that 2-hydroxycyclohexanone did not function as the precursor to the ring-contracted acid. From the results obtained from a study of the oxidation of 2,2,6,6-[Pg.196]

The recently reported (757) conversion of 5-pyrazolones directly to a,j8-acetylenic esters by treatment with TTN in methanol appears to be an example of thallation of a heterocyclic enamine the suggested mechanism involves initial electrophilic thallation of the 3-pyrazolin-5-one tautomer of the 5-pyrazolone to give an intermediate organothallium compound which undergoes a subsequent oxidation by a second equivalent of TTN to give a diazacyclopentadienone. Solvolysis by methanol, with concomitant elimination of nitrogen and thallium(I), yields the a,)S-acetylenic ester in excellent (78-95%) yield (Scheme 35). Since 5-pyrazolones may be prepared in quantitative yield by the reaction of /3-keto esters with hydrazine (168), this conversion represents in a formal sense the dehydration of /3-keto esters. In fact, the direct conversion of /3-keto esters to a,jS-acetylenic esters without isolation of the intermediate 5-pyrazolones can be achieved by treatment in methanol solution first with hydrazine and then with TTN. 

The potassium derivatives obtained from the reaction mixture are typically not isolated in pure form, and the crude products are often converted directly to the thallium complexes by metathesis with either thallium nitrate or thallium acetate [Eqs. (1) and (2)]. 

The technique of performing halide abstraction via interaction of a metal halo complex with a silverd), thallium(I), or nitrosonium salt (see ref. 142, for discussion) has proved useful in the isolation of many novel sulfoxide complexes. Thus, [Pd(S-Me2S0)2(0-Me2S0)2]-... 

The B oH o2 anion is best obtained by heating [Et3NH]2[BioHi2] to 160 °C. Its alkali metal salts are soluble in water, while the thallium salt is insoluble. The white alkali metal salts are stable up to 500 °C. Their aqueous solutions react neutral because the corresponding acid is a strong acid. It can be isolated as [H30]2[B1oH1o] (m.p. 202 °C) from its aqueous solutions obtained by ion exchange from the alkali metal salts. 

The only thallium compound to be discussed here is the Tlf,Cl2[Si(CMe3)3]6 cluster 61. This remarkable compound was formed by the reaction of thallium) 111) chloride with NaSi(CMe3)3 [Eq. (28)] and precipitated in the form of black crystals in 21% yield, when a solution in toluene was stored at —25 °C for six months [92], Solutions of 61 in benzene decompose slowly at room temperature by the formation of ClSi(CMe3)3 and a black, not identified precipitate. The structure of 61 consists of two four-membered T13C1 heterocycles, which are connected by one Tl-Tl and two Tl-Cl bonds. A monomeric TI3CI heterocycle was isolated as a byproduct in which one thallium atom was bonded to two Si(CMe3)3 substituents. 

Displacement reactions at Pm have been carried out with the thallium salt of cyclopentadiene, and various phosphinocyclopentadienes (28) isolated.29 Triphenyl-... 

Notes on cluster phases in triel alloys. Li and Corbett (2004) have shortly reviewed the systematic and extensive experimental and theoretical work carried out by Corbett and co-workers (see for instance Corbett 1996). Considering alkali metal-triel alloys, they underlined, particularly for Ga, In and Tl, the richness of their chemistry (see also 5.3.4.4). Gallium forms many anionic network structures (and only a few phases containing isolated cluster units), indium gives several examples of both network and discrete cluster structures, thallium forms especially discrete clusters (Tl , T157A Tl , Tl , Tl(f, Tl ). 

Many of the salts which have been prepared are explosive and sensitive to heat or impact. These include chlorites of copper (violent on impact), hydrazine (monochlorite, inflames when dry), nickel (explodes at 100°C but not on impact), silver (at 105° or on impact), sodium, tetramethylammonium, mercury, thallium and lead (which shows detonator properties). Several other chlorites not isolated and unstable in solution include mono-, di- and tri-methylammonium chlorites. The metal salts are powerful oxidants [1], Chlorites are much less stable than the corresponding chlorates, and most will explode under shock or on heating to around 100°C [2], Individually indexed compounds are ... 

Significant amounts of the bicyclo[3.3.1]nonane adduct and of the octahydropental-enes were isolated also from the reaction of 3 with preformed iodine acetate and iodine acetate thallium (equation 75)94 whereas only the monocyclic 1,2-adducts were obtained from treatment of 3 with iodine azide, iodine isocyanate or iodine nitrate95. The different propensity to give transannular products with these latter reagents has been related to the different positive charge density on carbons in the corresponding iodonium ion intermediates. 

The lack of homopolyatomic anions for elements to the left of group IV In Table I is noteworthy. Zlntl reported no success with reactions of alkali metal alloys of the copper and zinc family elements and of thallium with liquid ammonia, and the generally stabilizing effect of crypt has not been evident In our own Investigations of alloys of mercury and thallium. On the other hand. It is possible to Isolate a white crypt-potassium gold compound from ammonia solutions at low temperatures which decomposes to elemental gold (+ ) above about -10°C (30). 

Upon addition of perchlorate ions to the acetonitrile solutions, the salt [(MeCN)2ln Mn(C0)j 2]C104 can be isolated. This will react with pyridine or phenanthroline to yield [L2ln Mn(C0)5 2]C104 (L = py or phen). The compounds R4N[X4 In Mn(CO)5)J (n = 1—3 R = Me, X = Cl R == Et, X = Br) have also been prepared. Thus this work shows that as well as influencing the amount of dissociation of metal-metal bonded complexes, the nature of the solvent also determines the mode of ionization. The complex [TljMnlCOljlj] can be conveniently prepared from thallium(i) salts and [Na(Mn(CO)g ]. ... 

For secondary alkyl iodides, the two one-electron polarographic waves are more separated. Reduction of 2-iodooctane at the potential of the first wave alfords the dialkylmercury and 7,8-dimethyl-tetradecane by reactions of the sec-octyl radical. At the potential of the second wave only octane and octenes are isolated [37]. 2-Bromooctane shows only one polarographic wave and yields octane and octene on reduction at any potential [37]. Radicals generated by reduction of primary and secondary iodoalkanes will react with other cathode materials including tin, lead and thallium to form metal alkyls [48,49],... 

Although there seems to be no doubt that Six William Crookes was the first to observe the green line of thallium, many chemical historians, especially the French ones, attribute the isolation of the metal itself to Claude-Auguste Lamy. He was bom on July 15, 1820, at Ndry in the Jura department of France, attended the ficole Normale Supdrieure in Paris, and at the age of thirty-one years received his doctorate from Lille, He taught physics, first at Limoges and later at Lille (16). 

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