W(CO)3(Ph2PC2H4PPh2)(η2-Sc3N@Ih-C80/Sc3N@D5h-C80): regioselective synthesis and crystallographic characterization of air-stable mononuclear complexes of endohedral fullerenes

Abstract

The organometallic chemistry of endohedral metallofullerenes has lagged far behind that of empty fullerenes. Herein, we report a highly regioselective coordination reaction involving two Sc₃N@C₈₀ isomers and W(CO)₄(Ph₂PC₂H₄PPh₂) (1), which affords only one mononuclear complex for each Sc₃N@C₈₀ isomer (2a for Sc₃N@I_h-C₈₀ and 2b for Sc₃N@D_5h-C₈₀). X-ray results demonstrate that the tungsten center coordinates with the cages in an η² fashion on a [6,6]-bond in both cases, forming the first derivatives with a closed three membered ring for Sc₃N@C₈₀. Although IR and absorption spectroscopic results reveal relatively weak exohedral-metal to ligand π back-donation in both 2a and 2b, they show remarkable air-stability which promises their potential uses in related fields. Moreover, the coordination has narrowed down the electrochemical gaps of the parent Sc₃N@C₈₀ isomers, making the complexes better electron donors but worse electron acceptors than the corresponding precursors.