Gas-phase reactivity of the Ti ₈C ₁₂ ⁺ met-car with triatomic sulfur-containing molecules: CS ₂, SCO, and so ₂

Gas-phase Ti _xC _y ⁺ clusters (x/y = 3/5, 4/7, 5/9, 6/9, 7/12, 8/12, 9/12) including the magic Ti ₈C ₁₂ ⁺ (met-car) have been produced by reactive sputtering with a magnetron cluster source. The gas-phase reactivity of the met-car with SCO, CS ₂, and SO ₂ was investigated in a hexapole collision cell by way of tandem mass spectrometry. Results indicate an increase in activity as the oxygen-to-sulfur ratio increases (SO ₂ > SCO > CS ₂) with products ranging from association to break down of the met-car cluster. Trends in the mass spectra also indicate SCO and CS ₂ may bond to the met-car in a unique way not observed in previous reactivity studies on Ti ₈C ₁₂ ⁺. To investigate this, several possible single molecule-cluster bonding configurations were calculated with density functional theory. The results indicate that bridge bonding of the intact molecules is energetically preferred. In addition, the energy barriers and transition states leading to dissociation products were calculated and the trends are found to be in qualitative agreement with experiment. The effects of the different types of bonding and number of adsorbed species on the reactivity of the met-car along with proposed reaction mechanisms for product formation are also discussed.