64013-20-3Relevant academic research and scientific papers
Synthesis and reactivity of phosphine-stabilized phosphoranimine cations, [R3P·PR′2=NSiMe3]+
Huynh, Keith,Lough, Alan J.,Forgeron, Michelle A. M.,Bendle, Martin,Soto, Alejandro Presa,et al.
experimental part, p. 7905 - 7916 (2009/10/16)
A series of phosphine-stabilized phosphoranimine cations [R 3 P·PR′ 2 =NSiMe 3 ] + , which canbe regarded as derivatives of the proposed transient reactive intermedi ate [PR′ 2 =NSiMe 3 ] + in the thermalcondensation polymerization of phosphoranimines (R″O) PR′2 =NSiMe 3 to form poly(alkyl/arylphosphazenes) [PR′ 2 =N] n at 180-200°C, have been prepared. The bromide salts [R 3 P·PR′ 2 =NSiMe 3 ]Br [R′ = Me ([6] + ), OCH 2 CF 3 ([8] + ); R 3 P = Me 3 P (a), Et 3 P (b), n Bu 3 P (c), dmpm (d, dmpm = dimethylphosphinomethane), dmpe (e, dmpe = dimethylphosphinoethane)] were prepared from the direct reactions between BrMe 2 P=NSiMe 3 (5) and Br(CF 3 CH 2 O) 2 P=NSiMe 3 (7)and the corresponding tertiary phosphines R 3 P or the diphosp hines Me 2 P(CH 2 ) n PMe 2 (n = 1, 2). Cations of the type [6] + and [8] + , with electron-donating and -withdrawing groups at the phosphoranimine phosphorus center, respectively, undergo facile phosphine ligand substitution with the strong N-donor 4-dimethylaminopyridine (DMAP) to yield the corresponding DMAP-stabilized salts [DMAP·PR 2 =NSiMe 3 ]Br [R = Me ([9] + ), OCH 2 CF 3 ([10] + )]. Cations [6] + with Br - anions are particularly labile: for example, [6a]Br slowly releases PMe 3 , BrSiMe 3 , and forms cyclic phosphazenes such as [Me 2 P=N] 4 . Anion exchange reactions between the salts [6b]Br or [8c]Br and AgOTf (OTf = CF 3 SO 3 ) quantitatively afforded the corresponding and more stable triflate salts [6b]OTf and [8c]OTf.Phosphine ligand abstraction reactions with B(C 6 F 5) 3 were observed for the bromide salts [6b]Br and [8c]Br, which regenerated the phosphoranimines 5 and 7, respectively, and formed the adduct R 3 P·B(C 6 F 5 ) 3 . In contrast, the triflate salts [6b]OTf and [8c]OTf were unreactive under the same conditions. X-ray structural analysis of the P-donor stabilized cations revealed longer P-P and P-N bond lengths and smaller P-N-Si bond angles for cations [6] + compared to analogs [8] + . These structural differences were rationalized using the negative hyperconjugation bonding model. In addition, the ...
