Radical anions and group IVB organometallic adducts of nitrophenylacetylenes and some halogenated derivatives

The reactions of the title compounds with several reducing agents and with a number of Group IVB organometallic radicals has been investigated by electron spin resonance spectroscopy. In reducing media the ethynyl derivatives p- and m-NO2C6H4CCH were found to give the corresponding radical anions, while the halogenated compounds underwent a rapid halogen-hydrogen replacement. Depending on the experimental conditions the radical from p-nitrophenylacetylene was observed in different aggregation states with the positive counterion. Easy oxidation of the ethynyl group to the carbonyl function by adventitious oxygen was also observed in basic DMSO. On the contrary the expected oragnometalloxy nitroxides could be obtained in all cases, although prolonged irradiation of the p-NO2C6H4CCBr eventually led to substitution of Br by a H atom.