Steric Congestion and Reactivity in Cyclophosphazanes

Abstract

We have already demonstrated¹ that the cyclomphosphazane(1) is produced in the reaction of phosphorus oxychloride, POCl₃, with aniline hydrochloride. The formation of the mmer is proof that dimensation of a three-coordinated, λ⁵-phosphorus species, e.g. (2), is not occumng. The principal isomer of (1) formed is the trans form (la), but small amounts of the cis form, (lb), are also formed. Crystal structures of both isomers have now been determined, and

show that the ring exists as a twisted boat in (la) and as almost planar twisted chair and boat in the two crystallographic forms of (lb). The nitrogen atoms are planar, as is usual in P(V)-N compounds, but the planes of the nitrogen atoms are not coincident with the planes of the attached phenyl rings.