Thallium standard reduction potentials

The Tl -Tl relationship is therefore a dominant feature of thallium chemistry. The standard reduction potentials at 25 °C and unit activity of H+ are TIVtI = —0.336 V, T1 /T1 = +0.72 V, and Tl /Tli = +1.25V. Estimates have also been made for the couples T1 /T1 = +0.33 V and Tl /Tl = 2.22 V. The generally valid limitations concerning the use of standard electrode potentials to predict the redox chemistry of real systems are especially important in the case of thallium factors such as complex formation in the presence of coordinating anions or neutral ligands and pH dependence due to hydrolysis do affect the actual or formal redox potentials. For example, redox potentials have been measmed for TICI/TICI3 =+0.77 V in IM HCl and T10H/T1(0H)3 = —0.05 V in alkaline soluhon. These formal potentials differ from the standard value for Tiin/Tii = +1.25 V. The difference can be attributed to the substanhal difference between the complex forming abilities of Tl and Tl , which will be discussed in detail later. The... 

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 ... 

Recall from the discussion in Chapter 12 (pp. 310-311) that these half-reactions do not stand alone but rather must be measured versus another half-reaction such as the standard hydrogen electrode. (See Problems 14.24—14.26 for additional insight into the utility of the standard reduction potentials in thallium chemistry.)... 

B Use the standard reduction potential for thallium given in Table 14.2 for... 

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. 

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