Studies of phosphazenes. Part 31. Kinetic studies of the reactions of hexachlorocyclotriphosphazene with aromatic primary amines: evidence for the intermediacy of a reactive three-co-ordinated phosphorus(V) species

Abstract

Kinetic studies of the reactions of hexachlorocyclotriphosphazene with aromatic primary amines(aniline, p-toluidine, and p-anisidine) have been investigated with a view to developing ‘model systems’ for analogous reactions with aromatic diamines. The first and second stages of chlorine replacement proceed by an S_N2(P) mechanism in both tetrahydrofuran (thf) and methyl cyanide. Kinetic evidence is obtained for a base-catalysed E₁(c.b.) mechanism for the formation of geminal products in thf in the presence of an excess of tri-n-butylamine. The intermediacy of a three-co-ordinate P^V species is established by trapping experiments with methanol and by the isolation of the unusual products [NHEt₃][gem-N₃P₃CL₄(NHR)(O)][R = Ph, C₆H₄Me-p, or C₆H₄(OMe)-p]. These triethylammonium salts on dimethylaminolysis afford the hydroxy derivatives gem-N₃P₃(NHR)(OH)(NMe₂)₄, which exist in their oxophosphazadiene tautomeric forms.