TY - JOUR
T1 - Strain-Induced Ring-Opening Polymerization of Ferrocenylorganocyclotriphosphazenes
T2 - A New Synthetic Route to Poly(organophosphazenes)
AU - Allcock, Harry R.
AU - Dodge, Jeffrey A.
AU - Manners, Ian
AU - Riding, Geoffrey H.
PY - 1991/12/1
Y1 - 1991/12/1
N2 - The strained transannular ferrocenylcyclotriphosphazenes N3P3(OCH2CF3)4(η-CsH4)2Fe, N3P3R(0CH2CF3)3(η-C5H4)2Fe [R = OPh, R = Me, R = Ph (R geminal to Cp), and R = Ph (nongeminal to Cp)], and N3P3R2(OCH2CF3)2(η-C5H4)2Fe [R = Ph (geminal to Cp) and R = Ph (nongeminal to Cp)] undergo ring-opening polymerization when heated at 250 °C in the presence of a small amount (1%) of (NPC12)3, which functions as a polymerization initiator. The cyclic trimers N3P3-(OPh)(OCH2CF3)3(η-C5H4)2Fe, N3P3Me(OCH2CF3)3(η-C5H4)2Fe, and N3P3Ph2(OCH2CF3)2(η-C5H4)2Fe (Ph groups nongeminal to Cp) also polymerize at 250 °C but in the absence of (NPC12)3. These transformations are the first examples of uncatalyzed ring-opening polymerization of cyclic phosphazenes that lack phosphorus-halogen bonds. By contrast, the sterically crowded cyclotriphosphazene N3P3(OPh)4(η-C5H4)2Fe undergoes ring expansion to the corresponding cyclic hexamer when heated at 250 °C in the presence or absence of (NPC12)3, but it does not polymerize. When heated in the absence of (NPC12)3, N3P3(OCH2CF3)4(η-C5H4)2Fe, N3P3(OPh)(OCH2CF3)3(η-C5H4)2Fe, and N3P3Ph(OCH2CF3)3(η-C5H4)2Fe (Ph nongeminal to Cp) also undergo ring expansion to form the corresponding cyclic hexamers. The Lewis acid BC13 initiates the ring-opening polymerization of N3P3(OCH2CF3)4(η-C5H4)2Fe and catalyzes the ring expansion of N3P3(OPh)4(η-C5H4)2Fe. Possible explanations for the differences in thermal behavior are given. The implications of these results for the mechanisms of phosphazene ring-opening polymerization and ring-ring equilibration are also discussed.
AB - The strained transannular ferrocenylcyclotriphosphazenes N3P3(OCH2CF3)4(η-CsH4)2Fe, N3P3R(0CH2CF3)3(η-C5H4)2Fe [R = OPh, R = Me, R = Ph (R geminal to Cp), and R = Ph (nongeminal to Cp)], and N3P3R2(OCH2CF3)2(η-C5H4)2Fe [R = Ph (geminal to Cp) and R = Ph (nongeminal to Cp)] undergo ring-opening polymerization when heated at 250 °C in the presence of a small amount (1%) of (NPC12)3, which functions as a polymerization initiator. The cyclic trimers N3P3-(OPh)(OCH2CF3)3(η-C5H4)2Fe, N3P3Me(OCH2CF3)3(η-C5H4)2Fe, and N3P3Ph2(OCH2CF3)2(η-C5H4)2Fe (Ph groups nongeminal to Cp) also polymerize at 250 °C but in the absence of (NPC12)3. These transformations are the first examples of uncatalyzed ring-opening polymerization of cyclic phosphazenes that lack phosphorus-halogen bonds. By contrast, the sterically crowded cyclotriphosphazene N3P3(OPh)4(η-C5H4)2Fe undergoes ring expansion to the corresponding cyclic hexamer when heated at 250 °C in the presence or absence of (NPC12)3, but it does not polymerize. When heated in the absence of (NPC12)3, N3P3(OCH2CF3)4(η-C5H4)2Fe, N3P3(OPh)(OCH2CF3)3(η-C5H4)2Fe, and N3P3Ph(OCH2CF3)3(η-C5H4)2Fe (Ph nongeminal to Cp) also undergo ring expansion to form the corresponding cyclic hexamers. The Lewis acid BC13 initiates the ring-opening polymerization of N3P3(OCH2CF3)4(η-C5H4)2Fe and catalyzes the ring expansion of N3P3(OPh)4(η-C5H4)2Fe. Possible explanations for the differences in thermal behavior are given. The implications of these results for the mechanisms of phosphazene ring-opening polymerization and ring-ring equilibration are also discussed.
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U2 - 10.1021/ja00025a026
DO - 10.1021/ja00025a026
M3 - Article
AN - SCOPUS:0007150239
SN - 0002-7863
VL - 113
SP - 9596
EP - 9603
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 25
ER -