The sharing of electrons in the donor-acceptor complexes BH3NH3, BCl3NH3, AlH3NH3, AlCl3NH3, and GaCl3NH3 is investigated by the one-electron delocalization indices. Three prevailing aspects of the analysis are: (1) the nature of the compounds based upon the average number of electrons in atomic basins, (2) the quantitative extent of electron delocalization based upon the basin-basin indices, and,(3) the sharing of electrons between the groups constituting the molecules. Because the analysis is rooted in the first-order density matrix, no reference to orbitals has been invoked. This study provides new insight into the electronic basis of the DA interactions. (C) 2004 Elsevier B.V. All rights reserved.