Eur. Phys. J. D 45, 247-252 (2007)
https://doi.org/10.1140/epjd/e2007-00267-5

The hydrogenated aluminium trimer: a theoretical examination of the formation and interconversion pathways^*

Faculty of Chemistry, Wroclaw University, F. Joliot-Curie 14, 50-383 Wroclaw, Poland

Corresponding author: ^a jmoc@wchuwr.chem.uni.wroc.pl

Received: 15 May 2007
Revised: 6 August 2007
Published online: 21 September 2007

Abstract

Five doublet isomers of the Al₃H₂ cluster lying within a narrow range of 5 kcal/mol, along with the isomerization transition states connecting them, have been located with the coupled-cluster CCSD(T) and DFT methods. The two most stable doublet structures, the C_2v planar including the two Hs bound terminally and C₁ non-planar showing one H in terminal site and the other in threefold site are found to be essentially degenerate. Although the reaction of Al₃ with H₂ to yield Al₃H₂ is found to be significantly exothermic, by 23.5 kcal/mol, this hydrogenation is impeded by a considerable kinetic barrier of 16 kcal/mol. Our result is consistent with the observed lack of reactivity of Al_n towards H₂(D₂) for n=3 under thermal conditions [3]. The quartet Al₃H₂ isomers are predicted to lie 16–21 kcal/mol higher in energy than the doublet analogues. Further dimerization of Al₃H₂ to form Al₆H₄ has also been examined.