Three Salts Containing the Fullerene Tetra‐Anion C604– – Synthesis,X‐Ray Single‐Crystal Structure Determination and EPR Investigation

A synthesis for four‐fold negatively charged fullerides in solution is presented. Three salts containing discrete C₆₀^4– anions were synthesized by the reduction of C₆₀ in solution using rubidium‐mercury amalgams and rubidium suboxide both in the presence of elemental mercury. The three new salts, Rb₆DMF₁₄(C₆H₁₃N₂O₂)₂] · C₆₀ ( 1 ), Rb(diaza‐18‐crown‐6)]₄ · C₆₀ · (en)_4.1 ( 2 ), and Rb(benzo‐18‐crown‐6)]₄ · C₆₀ ( 3 ), were characterized by single‐crystal X‐ray diffraction. The results clearly indicate a charge of 4– for the fulleride anions. In 1 the fulleride units are ordered, and their distortion from I_h symmetry shows similarities to binary alkali metal fullerides that contain C₆₀^4– anions. In the crystal structures of 2 and 3 the C₆₀^4– anions show a rotational disorder. In all structures the 6:6 bond lengths within the fulleride are strongly enlarged compared to the ones in neutralC₆₀. EPR measurements reveal a singlet state for the C₆₀^4– anion.