Alkylation of Cyclic and High Polymeric Phosphazenes via Reactions between Aluminum Alkyls and Aminophosphazenes

(Dimethylamino)chlorophosphazenes react with (CH₃)₃A1, (C₂H₅)₂A1C1, or (C₂H₅)₃A1 to replace chlorine atoms geminal to the amino groups by alkyl units. Subsequent treatment of these products with hydrogen chloride brings about replacement of the dimethylamino groups by chlorine. These reactions have been investigated for cyclic phosphazene trimers that bear one, two, or three dimethylamino units, for cyclic phosphazene tetramers that bear two or four dimethylamino units, and for a mixed-substituent high polymeric phosphazene substrate. Chlorine replacement by aluminum alkyls is promoted by the electron-supplying character of the amino side groups, and three plausible mechanisms are presented. Alkylation is accompanied by phosphorus-nitrogen bond cleavage during reactions that involve the high polymer. The new cyclophosphazenes were characterized by elemental analysis, mass spectrometry, and ³¹P and ¹H NMR analysis. The high polymeric derivatives were also examined by gel permeation chromatography and differential scanning calorinaetry.