Unexpected formation of a phenonium ion-containing salt by single electron-transfer oxidation of a cage compound possessing triphenylamine moieties

The phenonium ion-containing salt 6-Cl+SbCl6− was unexpectedly generated in the tris(4-bromophenyl)aminium hexachloroantimonate-promoted, single electron-transfer oxidation reaction of 9,10-bis(4-diphenylaminophenyl)tetracyclo[6.2.0.04,10.05,9]decane (5). X-ray crystallographic analysis and quantum chemical calculations reveal that the cation in 6-Cl+SbCl6− contains a unique bridging phenonium ion structure that is stabilized by the presence of a cross-conjugated N,N-diphenyldivinyliminium ion (3-diphenylamino-1,3-cyclohexadienyl cation). It is noteworthy that 6-Cl+SbCl6− is a trapped product of a phenonium like radical cation 6+, the radical cation mutant of 2+.