The stability of RbHF and RbH2O complexes has been investigated by performing Hartree-Fock calculations on Rb · HF, H · RbF, and Rb · H2O species in various orientations. Heats of interaction of 2-5 kcal/mol are typically obtained. In each system, the free radical prefers to approach the dipolar molecule at the negative end. This preference cannot be explained by a simple point-dipole induced-dipole model; the finite size of the dipole is important and produces the directional sensitivity. These results indicate that such species should be stable in no-collision environments; such as the ultrahigh vacuum conditions in which RbH2O has been observed. © 1982 American Institute of Physics.