Formation of Single-Bonded (C60-)2 and (C70-)2 Dimers in Crystalline Ionic Complexes of Fullerenes

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Abstract
New ionic complexes of fullerenes C60 and C70 with decamethylchromocene Cp*2Cr·C60· (C6H4Cl2)2 (1), Cp*2Cr·C60·(C6H6)2 (2); the multicomponent complex of (Cs+)(C70-) with cyclotriveratrylene CTV·(Cs)2·(C70)2·(DMF)7·(C6H6)0.75 (3); bis(benzene)chromium Cr(C6H6)2·C60·(C6H4Cl2)0.7 (4), Cr(C6H6)2·C60·C6H5CN (5), Cr(C6H6)2·C70·C6H4Cl2 (6), Cr(C6H6)2·C60 (7); cobaltocene Cp2Co·C60·C6H4Cl2 (8), Cp2Co·C70·(C6H4Cl2)0.5 (9); and cesium Cs·C70·(DMF)5 (10) have been obtained. The complexes have been characterized by the elemental analysis, IR-, UV−vis−NIR spectroscopy, EPR and SQUID measurements. It is shown that C60•- exists as a single-bonded diamagnetic (C60-)2 dimer in 1, 2, 4, 5, and 8 at low temperatures (1.9−250 K). The dimers dissociate above 160−250 K depending on donor and solvent molecules involved in the complex. C60•- dimerizes reversibly and shows a small hysteresis (70-)2 dimers are also formed in 6, 9, and 10 and begin to dissociate only above 250−360 K. The IR and UV−vis−NIR spectra of σ-bonded negatively charged fullerenes are presented.