Oçafrain Maïténa, Herranz M Angeles, Marx Lucien, Thilgen Carlo, Diederich François, Echegoyen Luis
Laboratorie IMMO 2, Boulevard Lavoisier, 49045 ANGERS Cedex, France.
Chemistry. 2003 Oct 6;9(19):4811-9. doi: 10.1002/chem.200304935.
Four methanofullerene derivatives, with phosphonate or sulfone groups attached to a C(60) core through a Bingel procedure, were synthesized to probe their stability upon electrolytic reduction. Derivatives 1 and 2 are the most stable upon electroreduction and do not exhibit retro-cyclopropanation reactions until more than three electrons per C(60) derivative are transferred. The cyclopropane ring is then removed and C(60)(>CH(2))(n) (n=1-3) products result from reactions of the trianion of C(60) with the solvent, CH(2)Cl(2). The situation with diphosphonate 3 or phosphonatecarboxylate 4 is dramatically different. For 3, quantitative retro-cyclopropanation occurs when 2.8 e(-) per molecule are transferred. In the case of 4, when more than two electrons per molecule are transferred, there is evidence of the reversible formation of a very stable intermediate, which is oxidized at a potential 500 mV more positive than the first fullerene-based reduction of the parent compound. Electrolysis of a simple C(70)-Bingel monoadduct (5) also exhibits the formation of a similar intermediate. On the basis of cyclic voltammetry, ESR spectroscopy, and MALDI analysis of products, the intermediate observed during the electrolysis of compounds 4 and 5 is assigned to a dimeric structure.
通过Bingel反应合成了四种在C(60)核心上连接有膦酸酯或砜基团的甲烷富勒烯衍生物，以探究它们在电解还原时的稳定性。衍生物1和2在电还原时最稳定，直到每个C(60)衍生物转移超过三个电子时才会发生环丙烷逆反应。然后环丙烷环被去除，C(60)(>CH(2))(n)（n = 1 - 3）产物是由C(60)的三阴离子与溶剂CH(2)Cl(2)反应生成的。双膦酸酯3或膦酸酯羧酸盐4的情况则截然不同。对于3，当每个分子转移2.8个电子时会发生定量的环丙烷逆反应。对于4，当每个分子转移超过两个电子时，有证据表明形成了一种非常稳定的中间体，该中间体在比母体化合物基于富勒烯的首次还原电位更正500 mV的电位下被氧化。简单的C(70)-Bingel单加合物（5）的电解也显示出形成了类似的中间体。基于循环伏安法、电子自旋共振光谱和产物的基质辅助激光解吸电离分析，在化合物4和5电解过程中观察到的中间体被确定为二聚体结构。
