An ESR study of the mercuration of the biphenylene radical cation. Evidence for a homolytic mechanism of mercuration

Article abstract of DOI:10.1016/0022-328X(88)89063-6

When a solution of biphenylene in trifluoroacetic acid containing mercury(II) trifluoroacetate is photolysed with ultraviolet light, the ESR spectra show the progressive mercuration of the biphenylene radical cation in the β-position. β-Proton hyperfine coupling β) 76-77 G> appear until tetra-β-mercuration is complete.It is concluded that, apart from the usual electrophilic mechanism, an alternative mechanism for mercuration exists, and that this probably involves collapse of the aromatic radical cation, ArH^+., with its counterion, HgX2^-.: ArH + HgX2 -> ArH^+. + HgX2^-. -> HArHgX2 -> ArHgX + HX.