The solid/gas structural differences in the weak donor-acceptor complex BH3NH3 is theoretically studied using density functional and the topological analysis of the electron density. The analysis shows that the cooperative dihydrogen interactions are not the main organizing factors in the molecular aggregations affecting donor-acceptor bond lengths. These aggregations. are primarily controlled by electrostatic dipole dipole interactions. This fact can be exploited in the development of simple electrostatic models that will allow the prediction of the basic structure of supramolecular architecture.