Synthesis of Poly(alkyl/arylphosphazenes) via the Ambient Temperature Phosphite-Mediated Chain-Growth Polycondensation of (N-Silyl)bromophosphoranimines

Abstract

The room temperature addition of stoichiometric amounts of trimethyl phosphite, P(OMe)3, to N-silyl(halogeno)organophosphoranimines BrRR′P═NSiMe3 in chlorinated solvents led to the direct formation of high molecular weight polyphosphazenes [RR′P═N]n. The majority of polymerizations were complete within 18 h. The polymers prepared include poly(dialkylphosphazenes) (e.g., [nBu2P═N]n 1b), poly(alkylarylphosphazenes) (e.g., [PhMeP═N]n 1d), new materials featuring unsaturated substituents (e.g., [nHex{H2C═C(H)CH2}P═N]n 1n), and random copolymers (e.g., {[PhMeP═N]x−[PhnBuP═N]y} where x:y = 2:1, 7a). The precursor silylaminophosphines RR′P−N(SiMe3)2 (5a−q) and bromo(silylamino)phosphoranimines BrRR′P═NSiMe3 (4a−q) were synthesized and fully characterized prior to polymerization studies. The presence of alkoxy, carboranyl, and/or phenyl substituents on the N-silylbromophosphoranimines, as found in BrEt[CF3CH2O]P═NSiMe3 (4g), Br(2-[Me]-o-C2B10H10)EtP═NSiMe3 (4h), or BrPh2P═NSiMe3 (4i), respectively, was found eith...