Regioselective Cage Opening of La₂@D₂(10611)‐C₇₂ with 5,6‐Diphenyl‐3‐(2‐pyridyl)‐1,2,4‐triazine

Abstract

The thermal reaction of the endohedral metallofullerene La2@D2(10611)‐C72, which contains two pentalene units at opposite ends of the cage, with 5,6‐diphenyl‐3‐(2‐pyridyl)‐1,2,4‐triazine proceeded selectively to afford only two bisfulleroid isomers. The molecular structure of one isomer was determined using single‐crystal X‐ray crystallography. The results suggest that the [4+2] cycloaddition was initiated in a highly regioselective manner at the CC bond connecting two pentagon rings of C72. Subsequent intramolecular electrocyclization followed by cycloreversion resulted in the formation of an open‐cage derivative having three seven‐membered ring orifices on the cage and a significantly elongated cage geometry. The reduction potentials of the open‐cage derivatives were similar to those of La2@D2‐C72 whereas the oxidation potentials were shifted more negative than those of La2@D2‐C72. These results point out that further oxidation could occur easily in the derivatives.

Regioselective Synthesis, Crystallographic Characterization, and Electrochemical Properties of Pyrazole‐ and Pyrrole‐Ring‐Fused Derivatives of Y2@C3v(8)‐C82

“…Although the chemical behaviors of mono‐EMFs and metal nitride cluster EMFs have been widely studied, the properties of dimetallofullerenes (di‐EMFs) remain largely unexplored . To date, the functionalization of di‐EMFs is mainly focused on La 2 @ D 2 (10 611)‐C 72 and M 2 @ I h (7)‐C 80 (M=La, Ce, Gd, Tb, Dy, Ho, Er, Y) . Generally, the reactions on M 2 @ I h (7)‐C 80 afford only one or two mono‐adducts due to its high cage symmetry, whereas that of La 2 @ D 2 (10 611)‐C 72 is so low that as many as six mono‐adducts and seventeen bis‐adducts were formed in the reactions .…”