A wide range of these compounds have been made involving lithium, alkaline earth metals and lanthanides, and their structures determined using crystallographic techniques such as X-ray crystallography.
Structurally one of their interesting features is the presence of polyatomic anions of boron and nitrogen where the geometry and the B–N bond length have been interpreted in terms of π-bonding.
[3] Examination of the crystallographic data shows the presence of polyatomic units consisting of boron and nitrogen.
Bonding calculations show that the energy of the valence orbitals of metal atoms of group 2 and lanthanide elements are higher than those of the bonding orbitals in BNx ions which indicates an ionic like interaction between a metal atom and a BNx ion.
[4] For comparison purposes the following are considered to be typical BN bond lengths[1]