Gas-Phase Photodissociation of FeCH₂ ⁺ and CoCH₂ ⁺: Determination of the Carbide, Carbyne, and Carbene Bond Energies

Photodissociation of MCH₂⁺ (M = Fe, Co) is observed to yield three products M⁺, MC⁺, and MCH⁺. This result is in contrast to the low-energy collision-induced dissociation of MCH₂⁺, which yields M⁺ exclusively. From the photoappearance thresholds of the products, the following bond energies are assigned: D°(Co⁺-CH₂) = 84 ± 5 kcal/mol, D°(Co⁺-CH) = 100 ± 7 kcal/mol, D°(Co⁺–C) = 90 ± 7 kcal/mol, D°(Fe⁺–CH₂) = 82 ± 5 kcal/mol, D°(Fe⁺–CH) = 101 ± 7 kcal/mol, and D°(Fe⁺–C) = 94 ± 7 kcal/mol. Compared to the results of an earlier ion-beam study, the Co⁺–CH₂bond energy reported here is in excellent agreement while the Fe⁺–CH₂value is significantly lower.