Copper-dioxygen complexes and their roles in biomimetic oxidation reactions - Advances in Catalytic Activation of Dioxygen by Metal Complexes - page 109

Under an atmosphere, neat alcohol substrates (with a catalytic amount of
base) are converted to aldehydes or ketones, catalytically, some with more
than 1,000 turnovers. The mechanistic scheme, (Scheme 11), has been

deduced from studies with [Cu(BSP)] and benzyl alcohol using kinetic

measurements and kinetic-isotope effects (KIE = 5.3) plus Hammet

-substituted benzylic alcohols. These data
are consistent with bond cleavage in the rate-determining step.
Hydrogen atom transfer is suggested to occur from substrate to the
coordinated phenoxyl-radical, leading to release of the -OH moiety from the
reduced Cu(I)-product complex. Two-electron oxidation of [Cu(I)(BSP)] - to
form is suggested. While no direct spectroscopic
evidence is available for the hydroperoxo complex
product of dioxygen reaction, its formation is inferred from an observed
and the fact that it is EPR silent.
Recently, Wieghardt and co-workers reported a dinuclear
phenoxyl radical species that catalyzes the aerobic oxidation of primary and
secondary alcohols to the corresponding aldehyde, ketone and /or 1,2-glycol
derivatives as well as generating

relationships with para

uptake (aldehyde product :

This work has been reviewed

elsewhere. 115-117 More recently, Wieghardt and co-workers 119

reported on a

mononuclear catalyst that selectively oxidizes primary

alcohols with to aldehydes, forming The tridentate ligand can

be easily oxidized to the radical dianion and then to the diamagnetic

monoanion (Scheme 12). When was mixed with

in under anaerobic conditions in the presence of

excess then exposed to air at 20 °C, the neutral complex

forms. The crystal structure of complex shows that the

ion in exists in a slightly distorted square-planar environment. The
compound has a diamagnetic ground state due to the
antiferromagnetic coupling between the ion and the ligand radical. When
a solution of in THF is treated with the benzyl and ethyl
alcohol under anaerobic condition, it yields the corresponding aldehydes and
probably On the other hand, catalytic oxidations of
primary alcohols are observed when a THF solution of was
mixed with large excess of benzyl alcohol or ethanol as substrates and stirred