A Mn(III)-superoxo complex of a zwitterionic calix[4]arene with an unprecedented linear end-on Mn(III)-O-2 arrangement and good catalytic performance for alkene epoxidation

Reactions of [H4L][PF6](4) with 4 equiv. of Mn(OAc)(2)center dot 4H(2)O in the presence of air gave rise to a mononuclear Mn(III)-superoxo complex [Mn(III)L(O-2)(H2O)](PF6)(2), which contains a bowl-shaped cationic structure with a D-4d symmetry. It has an unprecedented linear end-on Mn(III)-O-2 unit and exhibited good efficiency and selectivity in the catalytic oxidation of alkenes with O-2 plus isobutyraldehyde under mild conditions.