text: The molecule adopts a structure similar to that of ethane, with which it is isoelectronic. The B−N distance is 1.58(2) Å. The B−H and N−H distances are 1.15 and 0.96 Å, respectively. Its similarity to ethane is tenuous since ammonia borane is a solid and ethane is a gas: their melting points differing by 284 °C. This difference is consistent with the highly polar nature of ammonia borane. The H atoms attached to boron are hydridic (negatively charged) and those attached to nitrogen are acidic (positively charged).
  The structure of the solid indicates a close association of the NH and the BH centers. The closest H−H distance is 1.990 Å, which can be compared with the H−H bonding distance of 0.74 Å. This interaction is called a dihydrogen bond. The original crystallographic analysis of this compound reversed the assignments of B and N. The updated structure was arrived at with improved data using the technique of neutron diffraction that allowed the hydrogen atoms to be located with greater precision.