Structure and properties of ionic fullerene complex Co+(dppe)2·(C60˙−)·(C6H4Cl2)2: distortion of the ordered fullerene cage of C60˙−radical anions

Abstract

New ionic complex {Co⁺(dppe)₂}·(C₆₀˙⁻)·(C₆H₄Cl₂)₂ (1) was obtained by the reduction of a Co(dppe)Br₂ and C₆₀ mixture by TDAE in o-dichlorobenzene followed by precipitation of crystals by hexane. Optical and EPR spectra of 1 indicated the formation of C₆₀˙⁻radical anions and diamagnetic Co⁺(dppe)₂ cations. The structure of 1 solved at 100(2) K involves chains of C₆₀˙⁻ arranged along the lattice a-axis with a center-to-center distance of 10.271 Å. The chains are separated by bulky Co⁺(dppe)₂ cations and solvent molecules. All components of 1 are well ordered allowing the distortion of the C₆₀˙⁻radical anion to be analyzed. An elongation of the C₆₀˙⁻ sphere by 0.0254(2) was found. It is essentially smaller than those in the salts (Cp*₂Ni⁺)·(C₆₀˙⁻)·CS₂ and (PPN⁺)₂·(C₆₀²⁻) with greater distortion of the fullerene cage. The calculation of the electronic structure of fullerene by the extended Hückel method showed slight splitting of the C₆₀ LUMO, due to the distortion, by three levels. Two levels are located 180 and 710 cm⁻¹ higher than the ground level. The averaged 6–6 and 5–6 bonds in C₆₀˙⁻ with lengths of 1.397(2) and 1.449(2) Å are close to those determined for the C₆₀²⁻ dianions in (PPN⁺)₂·(C₆₀²⁻), but are slightly longer and shorter, respectively, than the length of these bonds in neutral C₆₀.