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.
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.
Yang
Wei-Wei
WW
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.
Li
Zong-Jun
ZJ
Gao
Xiang
X