Adducts of Group IVB radicals with 4-alkylthio- and 4-alkyl-sulphonyl-pyridines. An ESR study

An electron spin resonance investigation on the paramagnetic adducts produced by attack of photolytically generated triphenylsilyl and triphenylgermyl radicals at the heterocyclic nitrogen of pyridines 4-substituted with alkylthio and alkylsulphonyl groups, is reported. The nitrogen and ring proton hyperfine splittings are strongly dependent on the nature of both substituent and entering organometal radical. The latter groups behave as acceptors for the unpaired electron, the electron-withdrawing ability being larger for SiPh3 than for GePh3. The experimental results also provide evidence that in the adducts of 4-butylthiopyridine, the preferred position of the bulky alkyl substituent deviates significantly from co-planarity with the aromatic ring.