P(IV)-P(V) Coordinational Isomerism of Phosphorus N-α-Haloethylimines

Abstract

The semiempirical MNDO-PM3 method in supramolecular approximation was used to study the structure of (N-α-haloethylimino)chloro(o-phenylenedioxy)phosphoranes R¹ ₃CR²X-N-P(Cl)O₂C₆H₂(R³-m)₂, where R¹ = H, Cl, F, R² = R³ = H, Cl, and X = F, Cl, Br, and of their 1:2 solvates with chloroform, as well as alternative mechanisms of the P(IV)-P(V) holotropic rearrangement. It was found that the activation barrier of the sigmatropic rearrangement increases in the order Br < Cl < F, in parallel with increasing thermodynamic stability of a more stable phosphorane isomer with an axial-equatorial arrangement of the dioxaphos- phole ring. It was shown that the most favorable pathway of the phosphorus-carbon halotropic rearrangement of a phosphorus N-α-haloethylimine, both nonsolvated and solvated with two molecules of chloroform, is the sigmatropic transformation.