Copper-dioxygen complexes and their roles in biomimetic oxidation reactions - Advances in Catalytic Activation of Dioxygen by Metal Complexes - page 87

hemoglobin, and side-on binding, as in hemocyanin. Both may be combined

with stoichiometry, leading to a superoxo-
copper(II) and peroxo-dicopper(II) products, respectively. In addition, in
copper-dioxygen chemistry, a

and

stoichiometry can

or

lead to complexes with a dicopper or tricopper core containing
copper(III), respectively, as described below. Peroxo-tetracopper species are
now also known (see below), although it is unclear if they are directly formed
in

reactions.

2.1 Copper-Dioxygen Complex Generation; 1984-1999

The first case of reversible dioxygen (and CO) binding to copper,
where the reaction product was also proven to possess an intact O-O bond,
involves a dicopper complex with bridging phenoxide ligand. The x-ray
structurally characterized dicopper(I) complex reversibly

reacts with one mole of to form the adduct,

at -80 ºC

48

This species is a peroxo-dicopper(II) complex as determined from

resonance Raman and X-ray absorption
spectroscopic studies. 49-51 Structural insights from Extended X-ray
Absorption Fine Structure (EXAFS) spectroscopy and a
mixed isotope resonance Raman experiment 50 suggest the peroxo
ligand is terminally bound (possessing inequivalent O-atoms), consistent with
the presence of two peroxo-to-copper(II) charge transfer bands, assigned as
and (610 nm) transitions. serves as a
prototype for terminally bound peroxo-Cu complexes. 12,52 The kinetics and

(Cu...Cu = 3.31 Å)

(505 nm)