Structure and stability of M-H-2 complexes

The potential stability of van der Waals complexes M-H-2 (M = Li, Be, B, C, Na, Mg, Al, Si) is assessed using quadratic configuration interaction and large basis sets. It is found that the alkali metals and alkaline earths form very weak complexes in their ground states, but much stronger complexes in their (p) excited states. The elements B, Al, C, and Si form both linear (C-infinity upsilon) and perpendicular (C-2 upsilon) complexes, with greater thermodynamic stability in the latter arrangements. The complexes formed by C are likely to be kinetically unstable, and the same may be the case for Si. On the other hand, the complexes formed by B and Al are predicted to be quite stable.