Distortion and electronic structure of ordered C60•− radical anions in the salt with {CoI(dppe)2CO}+ cations (dppe: 1,2-bis(diphenylphosphino)ethane)

Abstract

Radical anion salt {CoI(dppe)2CO}+(C60•−)⋅0.5C6H4Cl2⋅0.5C6H14 (1, dppe: bis(diphenylphosphino)ethane) has been obtained at the C60 and CoII(dppe)Cl2 reduction by NaCpCo(CO)2. Cobalt is positioned in the center of a triangular bipyramid in {CoI(dppe)2CO}+ with two phosphorus and one carbon equatorial atoms and two axial phosphorus atoms with average Co-P distances of 2.2542(6) and 2.2180(6) Å, respectively. The salt is a rare example of structure with the ordered fullerene cage which shows small ellipsoidal distortions (elongation of the cage is only 0.016 Å). Calculations of electronic structure of C60•− by the extended Hückel method showed splitting of the C60 LUMO into three levels. Two levels are located by 589 and 887 cm−1 above the ground level. The CoI(dppe)2CO+ cations are diamagnetic, and magnetic susceptibility of 1 is defined only by C60•−. Magnetic moment of 1 is 1.86 μB at 300 K. The salt shows EPR signal with g = 1.9996 and linewidth of 6.93 mT at 295 K. EPR signal shifts to smaller g-factor and narrows with the temperature decrease allowing one to observe the splitting of the signal into two and finally three lines below 30 K most probably due to the transition from the dynamic to the static Jahn-Teller effect.