Reaction of Thianthrene Cation Radical with Diarylmercurials. Search for Single Electron Transfer Is Elusive

Abstract

Diarylmercurials (Ar2Hg) with Ar = p-tolyl Ib, o-tolyl Ic, p-anisyl Id and 2-allyloxy-4,5-dimethylphenyl Ie, reacted with thianthrene cation radical perchlorate (Th.+ClO4-) in two stoichiometric ratios: 2 : 1 and 4 : 1 (Th.+ClO4-/Ar2Hg). In the 2 : 1 ratio the products were the 5-arylthianthreniumyl perchlorates IIb - IIe, thianthrene (Th) and ArHg+ClO4- (assayed as ArHgCl, III) in quantitative yields. In the 4 : 1 ratio reaction with ArHg+ occurred, too, and the products were IIb - IIe, Th, the complex Th3Hg(ClO4)2 and HgO (after workup). In contrast, Ph2Hg (Ia) did not react beyond the 2 : 1 stoichiometry. In the reactions with Ie, no evidence for formation and cyclization of free 2-allyloxy-4,5-dimethylphenyl radical was found. Reaction of and product formation from these arylmercurials, therefore, does not occur in single electron transfer steps that lead to free aryl radicals. Instead electron transfer appears to occur within a complex of Ar2Hg with Th.+ from which II and other products are subsequently formed.