An electron spin resonance study of radical intermediates from 1,6,6aλ⁴-triheterapentalenes

Adduct radicals can be observed by e.s.r. spectroscopy on reaction of some reactive, transient radicals with 1,6,6aλ4-triheterapentalenes provided the atom at position 1 (and/or 6) is sulphur or selenium. The adduct radicals formed with tri-n-butylstannyl and trithiapentalenes have been studied in most detail. Trithiapentalene itself yields two adduct radicals and 2-t-butyltrithiapentalene yields three adduct radicals. It is concluded that all the adduct radicals are of the pentadienyl type, the Bun 3Sn· radical adding to S-1 (or S-6) and cleaving the S-1-S-6a (or S-6-S-6a) bond. The observation of more than one adduct radical from a single, symmetric, trithiapentalene is attributed to the fact that the adduct radical can exist in more than one conformation. Structures are tentatively assigned to most of the observed radicals.