“…Detailed reactivity ratio determinations show that, under the conditions of radical-initiated polymerization, the phosphazene ring acts as a strong σ-electron-withdrawing group; thus, the propagating radical is highly polarized and does not exhibit any significant resonance stabilization with the cyclophosphazene ring . This model is consistent with the electronic structure of these monomers as demonstrated by recent photoelectron spectroscopy investigations . In response to these observations, emphasis has been shifted to cyclophosphazene monomers in which an insulating group is interposed between the olefinic center and the cyclophosphazene.…”
Section: Introductionsupporting
confidence: 70%
“…7 This model is consistent with the electronic structure of these monomers as demonstrated by recent photoelectron spectroscopy investigations. 8 In response to these observations, emphasis has been shifted to cyclophosphazene monomers in which an insulating group is interposed between the olefinic center and the cyclophosphazene. Using this strategy, our group [1][2][3][4][5][6][9][10][11][12] as well as those of Inoue 1,13 and van de Grampel 1,14 have produced a wide range of polymers and copolymers with cyclotriphosphazenes as substituents.…”
The vinyloxycyclophosphazene derivatives, N3P3Cl5OCHCH2 (1) and N4P4Cl7OCHCH2
(6), undergo radical polymerization to produce the highly functionalized homopolymers [CH(ON3P3Cl5)CH2]
n
(7) and [CH(ON4P4Cl7)CH2]
n
(8). These materials undergo a remarkable two-step thermal
decomposition process. The first step is an exothermic cross-linking reaction involving the elimination of
HCl at modest temperatures. The activation energy for the first step is lower for 7 than for 8. The second
step is an endothermic elimination of the oxo-bridged cyclophosphazene dimer, (N3P3Cl5)2O. Copolymers
have been obtained from mixtures of 1 and 6. The calculated reactivity ratios show a preference for
incorporation of 1 over 6 into the copolymers. Attempted copolymerization of 1 with styrene leads to
mixtures of the respective homopolymers. Attempts to polymerize N3P3X5OCHCH2 [(X = F(2), OCH3
(3), OCH2CF3 (4), N(CH3)2 (5)] lead to various outcomes including insoluble materials, oligomers, or
recovery of unreacted monomer. The sensitivity of the polymerization to the nature of the phosphazene
substituents has been related to monomer electronic structure and reactivity of the exocyclic groups.
“…Detailed reactivity ratio determinations show that, under the conditions of radical-initiated polymerization, the phosphazene ring acts as a strong σ-electron-withdrawing group; thus, the propagating radical is highly polarized and does not exhibit any significant resonance stabilization with the cyclophosphazene ring . This model is consistent with the electronic structure of these monomers as demonstrated by recent photoelectron spectroscopy investigations . In response to these observations, emphasis has been shifted to cyclophosphazene monomers in which an insulating group is interposed between the olefinic center and the cyclophosphazene.…”
Section: Introductionsupporting
confidence: 70%
“…7 This model is consistent with the electronic structure of these monomers as demonstrated by recent photoelectron spectroscopy investigations. 8 In response to these observations, emphasis has been shifted to cyclophosphazene monomers in which an insulating group is interposed between the olefinic center and the cyclophosphazene. Using this strategy, our group [1][2][3][4][5][6][9][10][11][12] as well as those of Inoue 1,13 and van de Grampel 1,14 have produced a wide range of polymers and copolymers with cyclotriphosphazenes as substituents.…”
The vinyloxycyclophosphazene derivatives, N3P3Cl5OCHCH2 (1) and N4P4Cl7OCHCH2
(6), undergo radical polymerization to produce the highly functionalized homopolymers [CH(ON3P3Cl5)CH2]
n
(7) and [CH(ON4P4Cl7)CH2]
n
(8). These materials undergo a remarkable two-step thermal
decomposition process. The first step is an exothermic cross-linking reaction involving the elimination of
HCl at modest temperatures. The activation energy for the first step is lower for 7 than for 8. The second
step is an endothermic elimination of the oxo-bridged cyclophosphazene dimer, (N3P3Cl5)2O. Copolymers
have been obtained from mixtures of 1 and 6. The calculated reactivity ratios show a preference for
incorporation of 1 over 6 into the copolymers. Attempted copolymerization of 1 with styrene leads to
mixtures of the respective homopolymers. Attempts to polymerize N3P3X5OCHCH2 [(X = F(2), OCH3
(3), OCH2CF3 (4), N(CH3)2 (5)] lead to various outcomes including insoluble materials, oligomers, or
recovery of unreacted monomer. The sensitivity of the polymerization to the nature of the phosphazene
substituents has been related to monomer electronic structure and reactivity of the exocyclic groups.
“…Alternatively, the increased number of low lying excited states available with the unsaturated organic substituents allows for larger local paramagnetic term (σ p ) contributions as the cause of the trend in the phosphorus shifts. It is important to note that all evidence available argues against specific phosphorus–carbon multiple bonds, − but the global MOs of the molecules will contain contributions from the unsaturated carbon centers. A general understanding of substituent effects in phosphazene chemical shifts is lacking and would be of interest if it were to become available.…”
In contrast to previously studied reactions of ethynyl lithium reagents, the reactions of propynyl and hexynyl lithium with N(3)P(3)F(6) lead to predominantly nongeminal isomers. A modest cis stereo selectivity was observed. The sequential addition of a lithio acetylene reagent which follows a predominately geminal pathway (lithiophenylacetylene) and an aryl lithium reagent (p-propenylphenyl lithium) which follows a predominantly nongeminal pathway were examined. The relative order of addition of the two reagents was interchanged, resulting in a change of reaction pathway demonstrating ring substituent control of the regio and stereo chemical pathways. Hydrogenation of the ethynyl unit in the phosphazene derivatives provides a facile pathway to the difficult to prepare alkylphosphazenes. The chemical shift of the organosubstituted phosphorus center undergoes a remarkably large change (46-47 ppm) on going from the ethynyl to the alkyl derivatives, which reduces the complex (31)P and (19)F NMR spectra of the ethynyl derivatives to easily interpretable first-order spectra, thus allowing for structure assignment. The (13)C NMR data shows that nongeminal regio selectivity increases with the amount of s character on the ethynyl carbon atom attached to the phosphorus center. These observations allow for an understanding of the factors controlling regio and stereo chemical control in the reactions of carbanionic nucleophiles with N(3)P(3)F(6).
“…The chemistry of perfluorinated cyclophosphazenes differs significantly when compared to that of chloro and bromo analogues. The comparatively higher volatility, higher hydrolytic and thermal stabilities, and lower basicity of the ring nitrogens of fluorophosphazenes make them ideal precursors for phosphazene pendant polymers and for reactions with organometallic reagents. , Substitution of P−F bonds in the heterocycle by CsF-catalyzed desilylation of silylated alcohols, by mercaptans, and by CF 3 SiMe 3 has been a typical reaction of fluorophosphatriazenes. − Among perfluorinated phosphazenes, the behavior toward nucleophiles has also been found to vary. Reaction of [(CH 3 ) 2 N] 3 S[(CH 3 ) 3 SiF 2 ] (TASF) with N 3 P 3 F 6 has been reported to cleave the six-membered ring, while with N 4 P 4 F 8 and N 5 P 5 F 10 the same reaction results in the formation of stable perfluorinated cyclophosphazenate anions. , …”
Reactions of (CF2CH2OSiMe3)2 and CF2(CF2CH2OSiMe3)2 with N4P4F8 (1) in a 1:2.5 molar ratio resulted in the formation of monospiro compounds [(CF2CH2O)2PN](F2PN)3 (2) and [CF2(CF2)CH2O)2PN](F2PN)3 (4) as well as the intermolecular bridged compounds F7N4P4OCH2CF2CF2CH2OP4N4)F7 (3) and F7N4P4OCH2CF2CF2CF2CH2OP4N4F7 (5). An equimolar reaction of dilithiated 1,3-propanediol with 1 resulted in the 1,3-ansa-substituted compound CH2(CH2O)2[P(F)N]2(F2PN)2 (6) as the major product in good yield. However, an analogous reaction of the dilithiated 1,3-propanedithiol with 1 gave only the spirocyclic compound CH2(CH2S)2(PN)(F2PN)3 (8). The molecular structures of 2 and 6 were determined by single-crystal X-ray diffraction. In the presence of catalytic amounts of CsF in THF, the bridged compound 3 was converted to the spirocyclic compound 2 while the 1,3-ansa compound 6 under similar conditions transformed into the monospiro-substituted compound CH2(CH2O)2 (PN)(F2PN)3 (7). These transformations were monitored by time-dependent 19F and 31P NMR studies.
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