title: Reaction of C60(2-) with organic halides revisited in DMF: proton transfer from water to RC60- and unexpected formation of 1,2-dihydro[60]fullerenes.
abstract: The reactions of dianionic C(60) with organic halides, which have been studied extensively in benzonitrile (PhCN), are revisited in a different solvent medium, N,N-dimethylformamide (DMF), by using ArCH(2)Br (Ar = Ph, C(6)H(4)CH(3), C(6)H(4)Br). Interestingly, instead of the 1,4-R(2)C(60) adducts, which are the typical products when the reactions are carried out in PhCN, the 1,2-dihydro[60]fullerenes (1,2-HRC(60)) have been obtained as the major products in DMF, except for the case of o-CH(3)C(6)H(4)CH(2)Br probably due to the steric effect. The obtained 1,2-dihydro[60]fullerenes have been characterized with single-crystal diffraction, (1)H and (13)C NMR, high-resolution mass spectrometry (HRMS), and UV-vis. Further examination with deuterated reagents including PhCD(2)Br, DMF-d(7), and D(2)O has revealed that the fullerenyl hydrogen of 1,2-dihydrofullerenes originates from traces of water residue in DMF. When the reaction is re-examined in PhCN with the addition of an excessive amount of water, the yield of 1,2-dihydrofullerene increases significantly, but is still lower compared with that obtained in DMF, demonstrating a considerable solvent effect on the reactivity of C(60)(2-). A possible mechanism accounting for such a difference is proposed. The work has presented an alternative protocol for effective preparation of 1,2-dihydro[60]fullerenes, and may also provide clues toward a better understanding of the proton transfer process for anionic C(60)-mediated reducing reactions involving H(2)O.
authors.affiliation: State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Graduate School of Chinese Academy of Sciences, Chinese Academy of Sciences, 5625 Remin Street, Changchun, Jilin, 130022, China.
authors.forename: Wei-Wei
authors.initials: WW
authors.lastname: Yang
authors.forename: Zong-Jun
authors.initials: ZJ
authors.lastname: Li
authors.forename: Xiang
authors.initials: X
authors.lastname: Gao