Anions thallate

Lead(IV) trifluoroacetate in TFAH is a very reactive electrophile that is capable of plumbylating less electron-rich arenes. Nonetheless, the use of trifluoroacetate anions in the plumbylation reactions should be avoided, because aryllead(IV) tri-fluoroacetates are unstable compounds that readily decompose to the corresponding aryl trifluoroacetates and biaryls [34—37, 40, 41]. It has been reported [41] that 4-FC6H4ArPb(TFA)3 is reasonably stable and can be isolated from the reaction of Pb(TFA)4/TFAH with fluorobenzene. A mechanistic study [41] indicated an electrophilic substitution path for the plumbylation reaction, which seemed to be substantially more para-selective than mercuration and thallation. For example, the plumbylation of toluene with Pb(OAc)4 in dichloroacetic acid has been reported [41] to occur with >90 % para-selectivity. 

Aside from thallation, trivalent thallium is best known as a versatile oxidant in organic chemistry many of the reactions proceed with unique rearrangements. Let us first consider one that does not involve rearrangement. Thus, thallium(III) triflate (see Section 1.14 for the structure of the triflate anion), which may be obtained from the more common thallium(III) nitrate by treatment with trifluoromethanesulfonic (triflic) acid in DMF, oxidizes acetophenone to its a-trifluoromethanesulfonyloxy derivative ... 

We won t write a mechanism for the formation of the organothallium intermediate it forms via thallation of the enol form of acetophenone, and we urge you to write out the details. A triflate anion, which got kicked out in the first step, then displaces the thallium, which simultaneously undergoes reductive elimination to produce Tl OTf ... 

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