Competition between halogen and hydrogen bonding in ND4ICl2

Hydrogen and halogen bonding are two of the most important intermolecular forces in chemistry and biology. NH4ICl2 consists of NH4+ cations and ICl2- anions, the latter of which deviates considerably from the symmetric geometry most often encountered. One of the I-Cl distances is at the upper end then of those previously reported for this ion; and is intermediate in length between an I-Cl bond and an I---Cl halogen bond, with the chlorine atom involved in several hydrogen bonds of varying strength. The other I-Cl bond is closer to that seen in ICl. Earlier NQR studies suggest that electronic structure of the ICl2? ion alters upon cooling to liquid nitrogen temperature because of changes in the reorientational motion of the ammonium ion. We will carry out a variable temperature experiment to investigate how hydrogen and halogen bonding respond to temperature when they comprise one system.