H(OEt2)2[P(1,2‐O2C6Cl4)3]: Synthesis,Characterization, and Application as a Single‐Component Initiator for the Carbocationic Polymerization of Olefins |
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Authors: | Paul W Siu Khatera Hazin Prof?Dr Derek P Gates |
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Institution: | Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1 (Canada), Fax: (+1)?604‐822‐2847 |
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Abstract: | The development of novel Brønsted acids featuring the hexacoordinate phosphorus(V) anion TRISPHAT]? { 1 ]?=P(1,2‐O2C6Cl4)3]?} are reported. The title compound, H(OEt2)2 1 ], was synthesized from 1,2‐(HO)2C6Cl4 (3 equiv) and PCl5 in the presence of diethyl ether. This compound was fully characterized by 1H, 31P and 13C NMR spectroscopy, X‐ray crystallography and elemental microanalysis. Dissolution of H(OEt2)2 1 ] in acetonitrile results in the slow precipitation of crystalline H(OEt2)(NCMe) 1 ], which was characterized by X‐ray diffraction; however, in CD2Cl2 solution the TRISPHAT]? anion protonated and ring‐opened. The weighable, solid H(OEt2)2 1 ] was found to be a competent initiator for the polymerization of n‐butyl vinyl ether, α‐methylstyrene, styrene and isoprene at a variety of temperatures and monomer‐to‐initiator ratios. At low temperatures, polymers with Mn>105 were obtained for n‐butyl vinyl ether and α‐methylstyrene whereas slightly lower molecular weights were obtained with styrene and isoprene (104<Mn<105). The poly(α‐methylstyrene) synthesized at ?78 °C is syndiotactic‐rich (ca. 87 % rr) whereas the polystyrene obtained at ?50 °C is atactic. The polyisoprene obtained possessed all possible modes of enchainment as well as branched and/or cyclic structures that are often observed in polyisoprene. |
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Keywords: | Brø nsted acids carbocations phosphorus polyolefins weakly coordinating anions |
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