Thallium oxidizing power

Thallium has the electronic configuration of [Xe]4/ " 5if 6i 6/), and forms compounds in the oxidation states I, II, and III. Thallium(II) derivatives are relatively rare. In general the bonding between T1(III) and a donor is more covalent in nature, whereas T1(I) compounds show more ionic behavior. Interactions between the T1(I) atoms of neighboring molecules are common. The theoretical explanation has been controversial." The coordination chemistry of T1(III) is complicated by the highly oxidizing power of thallium(III) in both aqueous and nonaqueous solutions. 

Pentavalent bismuth compounds are typically somewhat unstable and oxidizing. Quite a few are useful as oxidants in various organic transformations. The instability and oxidizing power of pentavalent bismuth is generally ascribed to the inert pair effect (Section 1.27), which we also encountered for thallium and lead. 

Thallium (1) salts are oxidized only by very powerful oxidizing agents, eg, MnO or Cl, iu acid solutions. The properties of the more important thallium compounds are Hsted in Table 2. 

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 ... 

There is much else which could be said about the properties of thallium(II) in aqueous solution, but there is not time to cover those here. Perhaps an interesting point to mention, however, is that it is a powerful oxidizing agent. In 1 M... 

Aromatic radical-cations are generated by pulse-radiolysis of benzene derivatives in aqueous solution. Radiolysis generates solvated electrons, protons and hydroxyl radicals. The electrons are converted by reaction with peroxydisulpbate ion to form sulphate radical-anion, which is an oxidising species, and sulphate. In another proceedure, electrons and protons react with dissolved nitrous oxide to form hydroxyl radicals and water, Hydroxyl radicals are then made to react with either thallium(i) or silver(i) to generate thallium(ii) or silver(ll) which are powerfully... 

Iodine(III) tnfluoroacetates (iodine tristrifluoroacetate and lodosobenzene bis-trifluoroacetate) resemble lead(IV), thallium(III) and mercury(II) reagents in their reactions but do not share the undesirable high toxicity typical for the heavy metals Iodine tristrifluoroacetate is a very powerful oxidant that can introduce the trifluoroacetoxy group even into alkanes [60 61] Because branched alkanes react ... 

Enhancement by strong acids such as TFA is a general feature of oxidations with metal acetates. Metal trifluoroacetates in TFA are much more powerful oxidants (electrophiles) than the corresponding acetates in acetic acid. Activation of the metal oxidant in TFA has been observed with co-balt(III)217 249,259,27S 276 manganese(III),237,275 lead(IV),277-281 thallium-(III),282-287 cerium(IV),288 289 and copper(II).290 Similarly, the electrophilic properties of copper(I)291 and mercury(II)292 acetates are strongly enhanced by replacement of acetate by trifluoroacetate. It has been proposed217,276 that the potent oxidizing properties of Co(III) trifluoroacetate are due to ionization to the cationic Co(III) species,... 

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. 

Thallium (Tl, at. mass 204.37) occurs in its compounds in the I and III oxidation states. Thallium(I) compounds are the more stable. Thallium(I) forms sparingly soluble compounds, white TlCl, yellow Til, and black TI2S, as well as thiosulphate and ammine complexes of low stability. Colourless Tl ions can exist only in strongly aeidic media since the brown hydroxide, Tl(OH)3, which has no amphoteric properties, is precipitated at pH values as low as 0.3. Thallium(ni) yields halide-, oxalate-, and tartrate complexes. T1(I) is oxidized to Tl(ni) only by powerful oxidants, e.g., Mn04 , aqueous Cl2, and aqueous Br2. 

Other oxidants like thallium(III) oxide, vanadium(V) oxyfluoride, palladium ) acetate, and ruthenium(IV) tetrakis(trifluoracetate) have been developed as powerful tools for the intramolecular biaryl coupling reaction [7,93,113]. Nevertheless, DDQ is still one of the most versatile reagents in oxidative coupling reactions (see Scheme 14 and 29 [82,114]). The highly strained dioxa[8](2,7)pyrenophane (65), portraying an overall curvature of nearly 90° for the pyrene subunit, was finally obtained from the mefa-cyclophanediene (66) by dehydrogenation with DDQ in refluxing benzene in 67% yield [114]. 

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