We propose a high-resolution powder neutron diffraction study of the archetypal donor-acceptor complexes (CD3)3N...I2; (CD3)3N...ICl; C5D5N¿ICl; and C5D5N¿IBr. These are the simplest structurally characterised donor-acceptor complexes known between an amine and a halogen/interhalogen. These complexes exhibit short N...I contacts and unusually long I-I; I-Cl; I-Br bond lengths. Our objective is to obtain definitive structures on these compounds. We will determine changes not only in the halogen/interhalogen moiety, but also in the ligands. These will be the first high resolution neutron diffraction structures of this class of compounds and will be of importance in accurately describing the bonding in these compounds. This is of relevance because of the recent recognition that these types of bonds (halogen bonds) can be used in the design of crystal structures.