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 intera
ction and large basis sets. It is found that the alkali metals and alk
aline 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.