Tin-containing anion-radical salts of thallium with three pyrocatechol ligands

When substituted o-benzoquinones (Q) are treated with tin amalgam, biradicals with bi- and tetravalent tin are formed. The biradicals can be reduced on the surface of an alkali metal to the corresponding anion radical. Two conformations with different shielding of the O atoms are observed spectrally, one of which undergoes a rapid intramolecular exchange and in the other this exchange is absent or proceeds slowly. It is proposed that the transition between these conformations occurs by rotation of the free-radical ligand about the Sn-O bond. In order to study further the structure of the conformers, they have synthesized anion radicals with a Tl+ cation, which by virtue of the magnetic properties of the cation (a large value for the nuclear magnetic moment of the 203Tl and 205Tl isotopes) provide more information when their EPR spectra are studied than anion radicals with cations of alkali metals. These anion-radical complexes are obtained