Activation of C2H6 and C3H8 by Gas-Phase Mo~+:Thermochemistry of Mo-Ligand Complexes

摘要

The kinetic energy dependences of the reactions of Mo~+(~6S)with ethane and propane have been studied using guided ion beam mass spectrometry.No exothermic reactions are observed in these systems,in contrast to results for the neighboring element,Nb~+.At slightly elevated energies,dehydrogenation of the two hydrocarbons is observed as the dominant process at low energies in both reaction systems.At high energies,products resulting from both C-H and C-C cleavage processes are appreciable.Modeling of the endothermic reaction cross-sections yields the 0 K bond dissociation energies(in eV)of D_0(Mo- H)= 2.06 ± 0.19,A)(Mo~+-H2)= 0.14 ± 0.15,D_0(Mo~+-CH)= 5.32 ± 0.14,D_0(Mo~+-CH3)= 1.57 ± 0.09,A>(Mo~+-C2H)= 3.25 ± 0.22,D_0(Mo~+-C2H2)> 1.87 ± 0.05,D_0(Mo~+-C2H3)= 2.95 ± 0.15,D_0(Mo~+-C2H4)> 0.82 ± 0.03,D_0(Mo~+-C2H5)= 2.09 ± 0.14,D_0(Mo~+-C3H2)= 4.34 ± 0.21,D_0(Mo~+-C3H4)= 2.22 ± 0.03,and D_0(Mo~+-C3H6)> 0.81 ± 0.05.The ionization energy of MoH is also derived as 7.43 ± 0.20 eV.The results for Mo~+ are compared to those for the first-row transition-metal congener,Cr~+,and the neighboring element,Nb~+.