Observation of a Cu(II)(2) (μ-1,2-peroxo)/Cu(III)(2) (μ-oxo)(2) equilibrium and its implications for copper-dioxygen reactivity.

Synthesis of small-molecule Cu2 O2 adducts has provided insight into the related biological systems and their reactivity patterns including the interconversion of the Cu(II) 2 (μ-η(2) :η(2) -peroxo) and Cu(III) 2 (μ-oxo)2 isomers. In this study, absorption spectroscopy, kinetics, and resonance Raman data show that the oxygenated product of [(BQPA)Cu(I) ](+) initially yields an "end-on peroxo" species, that subsequently converts to the thermodynamically more stable "bis-μ-oxo" isomer (Keq =3.2 at -90 °C).

Kinetics evidence for a complex between peroxynitrous acid and titanium(IV).

The reaction between TiO(2+) and ONOOH in 0.9 M H(2)SO(4) provides evidence for direct formation, previously unobserved, of a HOONO-metal complex. The reaction proceeds via formation of an end-on complex (k = 3.