Activation of C2H6, C3H8, HC(CH3)3, and c-C3H6 by gas-phase Ru+ and the thermochemistry of Ru-ligand complexes

The reactions of Ru⁺ with C₂H₆, C₃H₈, HC(CH₃)₃, and c-C₃H₆ at hyperthermal energies have been studied using guided ion beam mass spectrometry. It is found that dehydrogenation is efficient and the dominant process at low energies in all four reaction systems. At high energies, C-H cleavage processes dominate the product spectrum for the reactions of Ru⁺ with ethane, propane, and isobutane. C-C bond cleavage is a dominant process in the cyclopropane system. The reactions of Ru⁺ are compared with those of the first-row transition metal congener Fe⁺ and the differences in behavior and mechanism are discussed in some detail. Modeling of the endothermic reaction cross sections yields the 0-K bond dissociation energies (in eV) of D ₀(Ru-H)=2.27±0.15, D ₀(Ru⁺-C)=4.70±0.11, D ₀(Ru⁺-CH)=5.20±0.12, D ₀(Ru⁺-CH₂)=3.57±0.05, D ₀(Ru⁺-CH₃)=1.66±0.06, D ₀(Ru-CH₃)=1.68±0.12, D ₀(Ru⁺-C₂H₂)=1.98±0.18, D ₀(Ru⁺-C₂H₃)=3.03±0.07, and D ₀(Ru⁺-C₃H₄)=2.24±0.12. Speculative bond energies for Ru⁺=CCH₂ of 3.39±0.19 eV and Ru⁺=CHCH₃ of 3.19±0.15 eV are also obtained. The observation of exothermic processes sets lower limits for the bond energies of Ru⁺ to ethene, propene, and isobutene of 1.34, 1.22, and 1.14 eV, respectively.