H(OEt2)2[P(1,2-O2C6Cl4)3]: Synthesis, Characterization, and Application as a Single-Component Initiator for the Carbocationic Polymerization of Olefins

The development of novel BrOnsted 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 (3equiv) and PCl5 in the presence of diethyl ether. This compound was fully characterized by 1H, 31P and 13CNMR 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, -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 -methylstyrene whereas slightly lower molecular weights were obtained with styrene and isoprene (104<105). The poly(-methylstyrene) synthesized at -78 degrees C is syndiotactic-rich (ca. 87% rr) whereas the polystyrene obtained at -50 degrees 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.