This Letter contains a study of the interaction energy in HArF center dot center dot center dot N-2 and HArF center dot center dot center dot P-2 complexes. Symmetry-adapted perturbation theory (SAPT) has been applied to analyze the electrostatic, induction, dispersion and exchange contributions to the total interaction energy. The interaction energy has also been obtained by supermolecular method at the MP2, MP4, CCSD, CCSD(T) levels. The interaction energy for the studied complexes results from a partial cancelation of large attractive electrostatic, induction, dispersion terms by a strong repulsive exchange contribution. The induction and dispersion effects proved to be crucial in establishing the preference for the colinear HArF center dot center dot center dot N-2 and HArF center dot center dot center dot P-2 structures and shift direction of v(HAr) stretching vibrations. (C) 2008 Elsevier B.V. All rights reserved.