Phosphorus Halonitrides

On account of their stability towards heat and hydrolysing agents, as well as the requirements of valency, cyclic formulae have been assigned to the halonitrides in which the rings are composed either of >N—PCl₂ or of ≥N and ≥PCl₂ alternately. Thus the tri-compounds may be represented by

(a) or (b)

It has been supposed that the angle of least strain of the rings or polyhedra is 135°, which is most closely realised in the tetra-compound, which is also the most stable of the series. The structure assigned will determine that of the corresponding metaphosphimic acid which is produced by hydrolysis. Dimetaphosphimic acid, if its existence is admitted, could not be cyclic according to formula (a). Formula (b) is adopted in describing these compounds.