Halide-Promoted Dioxygenolysis of a Carbon–Carbon Bond by a Copper(II) Diketonate Complex

A mononuclear Cu­(II) chlorodiketonate
complex was prepared, characterized,
and found to undergo oxidative aliphatic carbon–carbon bond
cleavage within the diketonate unit upon exposure to O2 at ambient temperature. Mechanistic studies provide evidence for
a dioxygenase-type C–C bond cleavage reaction pathway involving
trione and hypochlorite intermediates. Significantly, the presence
of a catalytic amount of chloride ion accelerates the oxygen activation
step via the formation of a Cu–Cl species, which facilitates
monodentate diketonate formation and lowers the barrier for O2 activation. The observed reactivity and chloride catalysis
is relevant to Cu­(II) halide-catalyzed reactions in which diketonates
are oxidatively cleaved using O2 as the terminal oxidant.
The results of this study suggest that anion coordination can play
a significant role in influencing copper-mediated oxygen activation
in such systems.