ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Six candidate AlH5 structures were examined in detail using the self-consistent-field (SCF), configuration interaction including single and double excitations (CISD), and coupled cluster including single, double and perturbatively included connected triple excitations [CCSD(T)] methods in conjunction with double-ζ plus polarization (DZP), triple-ζ plus polarization (TZ2P), and augmented TZ2P(f,d) basis sets. The C4v and the D3h isomers are high in energy [72 and 84 kcal mol−1, respectively, relative to the Cs(I) structure at DZP CCSD]. Although structure Cs(I) is the global minimum, the second Cs form, where AlH5 is comprised of nearly planar alane (AlH3) and dihydrogen, is essentially equal in energy. Hence, the rotation of the hydrogen moiety is virtually free. The global Cs(I) minimum was characterized by vibrational frequency analyses at TZ2P CCSD(T). Final energies were obtained at CCSD(T) TZ2P(f,d). At room temperature, the alane–dihydrogen complex AlH5 is unstable toward dissociation by 3.1 kcal mol−1. However, at the absolute zero (0 K), the complex forms exothermically (−1.7 kcal mol−1). Hydrogen scrambling via the C2v (3) transition structure seems to be very unlikely since the activation barrier for this process is at least 24.6 kcal mol−1 higher than the dissociation energy of AlH5 into AlH3 and H2. © 1995 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.470540
Permalink
