Activation of H2 by Gadolinium Cation (Gd+): Bond Energy of GdH+ and Mechanistic Insights from Guided Ion Beam and Theoretical Studies

The energy-dependent reactions of the lanthanide gadolinium cation (Gd+) with H-2, D-2, and HD are investigated using guided ion beam tandem mass spectrometry. From analysis of the resulting endothermic product ion cross sections, the 0 K bond dissociation energy for GdH+ is measured to be 2.18 +/- 0.07 eV. Theoretical calculations on GdH+ are performed for comparison with the experimental thermochemistry and generally appear to overestimate the experimental GdH+ bond dissociation energy. The branching ratio of the products in the HD reaction suggests that Gd+ reacts primarily via a statistical insertion mechanism to form the hydride product ion with contributions from direct mechanisms. Relaxed potential energy surfaces for GdH2+ are computed and are consistent with the availability of both statistical and direct reaction pathways. The reactivity and hydride bond energy for Gd+ is compared with previous results for the group three metal cations, Sc+ and Y+, and the lanthanides, La+ and Lu+, and periodic trends are discussed.