Mechanism of formation of the peroxocarbonate complex (PCy3)2Ni(CO4) from solid (PCy3)2Ni(CO2) and dioxygen: an example of solid-state metallorganic reaction involving CO2 deco-ordination and reinsertion into the OO bond of (PCy3)2Ni(O2). Reactivity of the peroxocarbonate complex towards olefins in the solid state and in solution

Solid (PCy3)2Ni(CO2) (1) reacts with dioxygen to afford the peroxocarbonate complex (PCy3)2Ni(CO4) (3). The use of labelled 13CO2, C18O2, 18O2 coupled with a FTIR study of both the gas-phase in equilibrium with the solid and the solid resulting complex, allows to propose the reaction mechanism that implies CO2 deco-ordination, O2 co-ordination, and CO2 insertion into the OO bond of the newly formed, reactive (PCy3)2Ni(O2) complex 2. A normal mode analysis substantiates the band assignment and the proposed mechanism. Peroxocarbonate (3) exhibits a 13C resonance at 166.6 ppm and a single 31P signal at 43.1 ppm below 200 K. The reactivity of the peroxo-group as one-oxygen transfer agent prevents the spectroscopic characterisation of 3 in solution at room temperature. An out-of-sphere phosphine can be easily oxidised. A gaseous olefin, mono-ene (ethylene) or diene (allene), added to 3, makes easier the deco-ordination process of one phosphine ligand, that is then oxidised to phosphine oxide. The gaseous olefin itself is not oxidised until free phosphine is present in the medium. In solution, styrene is oxidised through a two- or one-oxygen transfer pathway, according to the reaction condition.