Crystal structure of phosphoric triamide

Abstract

Phosphoric triamide crystals are monoclinic, a= 8·40, b= 8·77, c= 5·42 Å, β= 94·5°, space group P2₁/c, Z= 4. The positions of all atoms, including hydrogen, have been determined from X-ray diffraction data and refined by a least-squares procedure. The molecule has a slightly distorted tetrahedral shape with a small, but significant, difference between the lengths of one P–N bond (1·648 Å) and of the other two (1·658, 1·661 Å). This arises from a difference in the hydrogen-bond environments of the three nitrogen atoms. The lengths of the P–N bonds suggest that they have about 30%π-bond order. All the hydrogen atoms take part in a three-dimensional network of weak hydrogen bonds, NH ⋯ O (lengths 2·93–3·18 Å) and NH ⋯ N (3·25 and 3·28 Å), which link the molecules together. Each oxygen atom forms four NH ⋯ O bonds with a spatial arrangement very similar to that in the urea crystal. The P–O bond length is 1·510 Å.