Hartree-Fock (HF) and density functional (B3LYP) calculations of geometrical, vibrational, magnetic, and energetic parameters of the endohedral Ih, structure of X@Al12H2-12 closo-alane and X@Ga12H2-12 closo-gallane anions with interstitial noble gas atoms and hydride and halide ions (X = Ng, H-, Hal-) in the center of icosahedral [Al12] and [Ga12] clusters were performed with the 6-31G* and 6-311+G** basis sets. For the majority of systems studied, the endohedral structure corresponds to a minimum on the potential energy surface, which is 28 (He), 52 (Ne) 158 (Ar), 180 (Kr), 78 (H-), 87 (F-). 199 (Cl-), and 210 (Br-) kcal/mol higher than the dissociation limit for alanes and 39 (He), 73 (Ne), 213 (Ar), 194 (Li+), and 120 (Na+) kcal/mol higher than the dissociation limit for gallanes. The potential energy barrier for the interstitial heteroatom X to come out through an edge (via the structure C2v(b)) or a face (structure C3v(t)) of the [Al12] cluster is rather high for light atoms and ions X = He, Ne, H-, and F- (20-50 kcal/mol). Thus, the endohedral Ih structure for these compounds (like for similar salts with the cation L = Li+, Na+, and Mg2+) is kinetically stabilized and can exist as a high-energy intermediate. Characteristic features of vibrational spectra and 27Al NMR chemical shifts for molecules with the endohedral Ih structure are considered from the standpoint of the possibility of their identification by IR and NMR spectroscopy. The trends in the structural, energetic, and spectral properties of the molecules with an increase in the radius and electronegativity of the central X atom upon its change along the sub-group and in isoelectronic series are considered, and the difference between the properties of alanes and gallanes is discussed.
|Number of pages||11|
|Journal||Russian Journal of Inorganic Chemistry|
|Publication status||Published - Jan 2001|