Abstract
Kinetic and thermodynamic parameters for metal ion-O
2 interaction have been obtained for a variety of copper(I) complexes with different binding modes for dioxygen. In general, favorable binding enthalpies of up to 80 kJ mol
−1 are compensated by strongly negative reaction entropies up to −220 J K
−1 mol
−1, restricting the range of overall stabilities. Sequential formation of superoxo and peroxo complexes, as well as concomitant formation of
η
1:
η
1 and
η
2:
η
2 μ-peroxo complexes has been established by low-temperature stopped-flow experiments. In several cases, pseudoreversible binding of dioxygen is followed by an irreversible oxidation of the organic ligand. A recent result is the identification of a rapid equilibrium between an
η
2:
η
2 μ-peroxo complex and the isomeric bis-μ-oxo compound with broken OO bond which may be fundamental to several O
2 dependent redox enzymes.