Gas-phase reactions of cationic molybdenum and tungsten monoxide with ethanol: a combined experimental/computational exercise

The ion/molecule reactions of molybdenum and tungsten monoxide cations MO⁺ (M═Mo, W) with ethanol have been studied by Fourier transform ion-cyclotron resonance mass spectrometry (FT-ICR MS) and density functional theory (DFT) calculations. As observed in the previously reported reactions of MO₂ ⁺ (M═Mo, W) towards ethanol, the dehydration of ethanol to give rise to the elimination of neutral C₂H₄ constitutes also the dominating reaction channel for the monoxides. Likewise, both systems result in a combined dehydrogenation/dehydration process, thus forming the ionic product MOC₂H₂ ⁺; moreover, the tungsten system presents two additional reaction channels: double dehydrogenation of ethanol with concomitant formation of the ionic product WO₂C₂H₂ ⁺ and the generation of C₂H₅ ⁺ which takes place by OH^? transfer from ethanol to the tungsten atom. This combined experimental/computational study of gas-phase ion molecule reactions may shed some new light on the mechanisms that occur in complex catalytic systems.