Samarium cation (Sm) reactions with H, D, and HD: SmH bond energy and mechanistic insights from guided ion beam and theoretical studies.

Author(s) Demireva, M.; Armentrout, P.B.
Journal J Chem Phys
Date Published 2018 Oct 28

Guided ion beam tandem mass spectrometry is used to study the reaction of the lanthanide samarium cation (Sm) with H and its isotopologues (HD and D) as a function of collision energy. Modeling the resulting energy dependent product ion cross sections from these endothermic reactions yields 2.03 ± 0.06 eV (two standard deviations) for the 0 K bond dissociation energy of SmH. Quantum chemical calculations are performed to determine stabilities of the ground and low-energy states of SmH for comparison with the experimentally measured thermochemistry. The calculations generally overestimate the SmH bond energy, but a better agreement between experiment and theory is achieved after correcting for spin-orbit energy contributions, with coupled-cluster with single, double and perturbative triple excitations/complete basis set [CCSD(T)/CBS] results reproducing the experiment well. In the HD reaction, the SmH product is observed to be favored over the SmD by about a factor of three, indicating that the reaction proceeds via a direct mechanism with short-lived intermediates. This is consistent with quantum chemical calculations of relaxed potential energy surface scans of SmH, which show that there is no strongly bound dihydride intermediate. The reactivity and hydride bond energy of Sm, which has a valence electron configuration typical of most lanthanides, are compared with previous results for the lanthanide cations La, Gd, and Lu, which exhibit configurations more closely related to the group 3 metal cations, Sc and Y. Periodic trends across the lanthanide series and insights into the role of the electronic configurations on hydride bond strength and reactivity with H are discussed.

DOI 10.1063/1.5053758
ISSN 1089-7690
Citation J Chem Phys. 2018;149(16):164304.

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