Controlling the reactivity of La@C 82 by reduction: reaction of the La@C 82 anion with alkyl halide with high regioselectivity.

Endohedral metallofullerenes have excellent redox properties, which can be used to vary their reactivity to certain classes of molecules, such as alkyl halides. In this study, the thermal reaction of the La@ C 2 v -C 82 anion with benzyl bromide derivatives 1 at 110 °C afforded single-bonded adducts 2 - 5 with high regioselectivity. The products were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and visible-near infrared spectroscopy. The reaction of La@ C 2 v -C 82 with alkyl halides using the same conditions showed no consumption of La@ C 2 v -C 82 , indicating that the reactivity of La@ C 2 v -C 82 toward alkyl halides was effectively increased by one-electron reduction. Single-crystal X-ray diffraction analysis of the single-bonded adduct 3a revealed the addition site of the p -methoxybenzyl group on La@ C 2 v -C 82 . Theoretical calculations indicated that the addition site carbons in neutral La@ C 2 v -C 82 have high spin density, whereas those in the La@ C 2 v -C 82 anion do not have high charge densities. Thus, the reaction is believed to occur via electron transfer, followed by the radical coupling of La@ C 2 v -C 82 and benzyl radicals, rather than by bimolecular nucleophilic substitution reaction of La@ C 2 v -C 82 anion with 1 .