Ab initio MP2/aug'-cc-pVTZ calculations have been carried out to determine the structures and binding energies of binary complexes formed by HBO with a series of small molecules A. Three different types of structures have been identified, which depend on the nature of A. In one structure A:HBO, HBO acts as a weak proton donor. In the second HBO:A, HBO is a relatively strong base. The third type of complex A parallel to HBO has HBO and A in an approximately parallel arrangement. The dipole moment of A influences both the type of complex formed and its binding energy. (C) 2012 Elsevier B.V. All rights reserved.