Regioselective Cage Opening of La-2@D-2(10611)-C-72 with 5,6-Diphenyl-3-(2-pyridyl)-1,2,4-triazine

摘要

The thermal reaction of the endohedral metallofullerene La-2@D-2(10611)-C-72, 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 C-72. 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 La-2@D-2-C-72 whereas the oxidation potentials were shifted more negative than those of La-2@D2C72. These results point out that further oxidation could occur easily in the derivatives.