Gas-phase reactions of an iridium(I) complex with dioxygen - Comparison to solution-phase reactivity

The unique advantage of working in the gas phase, i.e., in the absence of solvent and counterions, is that the intrinsic reactivity of a catalyst can be determined. Although back translation to solution-phase reactivity is not necessarily straightforward, both the similarities and the differences between gas-phase and solution-phase chemistry hold information useful to the analysis of complex reaction pathways. Here we describe the oxidation of an iridium-ethene complex with molecular oxygen in the gas phase. Contrary to the solution-phase reactivity, in the gas phase only one single product is formed, namely a peroxo-ethene complex. Also in contrast to solution, full conversion of the ethene complex into the peroxo-ethene product is observed in the 24-pole ion guide under near-zero collision energy conditions and at relatively high collision gas pressures (up to 100 mTorr). These differences can be explained by the fact that the electron transfer pathway that plays a dominant role for product formation in condensed phase is shut off under these conditions.