Modulation of the gas‐phase reactivity of W⁺ by carbonyl ligands: Activation of hydrocarbons by W(CO) x+ (x=1–4)

The gas‐phase reactions of W(CO) x+ (x=1–4) with methane, ethane, propane, ethene and propene have been studied in a Fourier transform ion cyclotron resonance mass spectrometer. Virtually all reactions observed involve hydrocarbon dehydrogenation, either single or double, a reactivity similar in type to what is observed with bare W⁺. The most reactive ion is W(CO) 2+ except for this ion, reactivity tends to diminish with increasing number of carbonyl ligands. Whenever there is sufficient internal energy available, CO detachment competes with H₂ loss. This is the case for ethene and propene, and in some cases with propane. However, this is strongly dependent upon the number of carbonyl ligands in the reacting ion. In most cases, product ions are themselves reactive with the neutral, leading to reaction sequences of various lengths. These sequences end either because the metal no longer has the appropriate number of non‐bonding electrons for inserting into a CH bond with low activation energy, or because of saturation of the coordination shell around the metal.