New directions in phosphoranimine chemistry: From cations to anions and monomers to polymers.

摘要

A series of nitrogen donor-stabilized N-silylphosphoranimine cations [N-donor·PR2=NSiMe3] + (N-donor = DMAP, 4,4'-bipyridine, quinuclidine R = Cl, Me, Me/Ph, Ph, OCH2CF3), prepared from reactions of the parent phosphoranimines XR2P=NSiMe3 (X = Cl, Br R = Cl, Me, Me/Ph, Ph, OCH2CF3) with nitrogen donors in the presence or absence of a halide abstracting silver salt, is reported. These cations exhibit an important relationship between the phosphoranimine substituent and the structural parameters of the cation, which has been rationalized by the negative hyperconjugation bonding model. Cationic phosphoranimines represent important model compounds for the postulated polymerization intermediate in the thermal condensation of neutral alkyl/aryl phosphoranimine monomers.Reactions between the phosphoranimine Cl3P=NMes* and tertiary phosphines R3P (R = nBu, Ph) yield the phosphinimine ClP=NMes* and dichlorophosphoranes R3PCl2 (R = nBu, Ph). These products were found to undergo further reactions to yield the phosphinamide anion [Cl2PNMes*]--.The preparation and structural characterization of phosphine donor-stabilized phosphoranimine cations [phosphine·PR=NSiMe3]+ (phosphine = Me3P, Et3P, nBu, dmpm, dmpe R = Me, OCH2CF3) is also reported. These cations also exhibit a relationship between the phosphoranimine substituent and the structural parameters, similar to the nitrogen donor-stabilized phosphoranimine cations. In addition, a large difference in the magnitude of the 1 JPP is observed for these species, which is also dependent on the phosphoranimine substituent.An ambient temperature route to poly(alkyl/aryl)phosphazenes was discovered from the reactions of P-bromo(alkyl/aryl)phosphoranimines BrR2P=NSiMe3 (R = Me, Me/Ph) and phosphites (RO) 3P (R = Me, Et, Ph, OCH2CF3). The reaction proceeds with an initial induction followed by a linear conversion of monomer to polymer.Reactions involving the phosphoranimine Cl3P=NSiMe3 with tertiary phosphines R3P (R = nBu, Ph) yield N-phosphinophosphoranimines R3P=NPCl2 (R = nBu, Ph) via a complex mechanism which involves a series of reductive dechlorination and condensation steps.The ambient temperature ring-opening polymerization of the cyclic hexachlorophosphazene trimer [Cl2P=N]3 is reported. The ring-opening polymerization of [Cl2P=N]3 is catalyzed by the N-silylated phosphazene cations [R3Si(N3P3Cl6)] + (R = Me, Et) coupled with very weakly coordinating carborane anions, and yields high molecular weight poly(dichlorophosphaznene) [Cl2P=N] n.