Protonation of phosphoric amides. Molecular orbital calculations on phosphinamide, H2P(O)NH2, and its protonated forms

Abstract

Ab initio SCF molecular orbital calculations were carried out on the amide H₂P(O)NH₂(IV) and its N-protonated H₂P(O)NH₃⁺(V), and O-protonated H₂P(OH)NH₂⁺(VI) forms using optimized geometries. The total energies as well as bond lengths and angles were obtained for each individual structure. Conjugate acid (VI) was found more stable than (V). The preferred conformations of (VI) involve the syn- and anti-periplanar arrangement of the nitrogen lone pair and the POH group. In order to investigate the possibility of the intramolecular hydrogen bonding in (VI) a potential energy surface involving OH torsion and inversion at nitrogen was generated.

The results obtained are related to the reactivity of phosphoric amides under acidic conditions.