Establishing the mechanism of Rh-catalysed activation of O-2 by H-2

Reductive activation of O-2 by H-2 with rhodium terpyridine complexes in H2O and CH3CN is described and the mechanism is fully elucidated. The rhodium complex extracts electrons from H-2 and reductively activates O-2 to form a peroxo active intermediate. This intermediate is able to oxidise triphenyl phosphine to triphenyl phosphine oxide. A model system constructed in CH3CN provides isolable analogues of catalytic intermediates in H2O, allowing a detailed look at each step in the catalytic cycle.