Polypentenylenes of varying cis and trans steric configurations have been synthesized from cyclopentene using binary and ternary catalytic systems based on WCl6 and three classes of organometallic compounds: organoaluminium, organotin and organosilicon. In several cases the distribution of the double-bond pair sequences has been determined from the fine structure of the C-13 NMR spectra. Analysis of the polymer microstructure indicated that the catalytic systems derived from WCl6 and organoaluminium compounds (Bu3iAl, Et3Al, Et2AlCl and EtAlCl2) gave mainly trans configuration of the carbon-carbon double bond and a random or slightly blocky distribution of the double-bond dyads. By contrast, catalysts derived from WCl6 and organotin (Et4Sn, Bu4Sn and Ph4Sn) and organosilicon (Me2(allyl)2Si) compounds led primarily to cis configuration of the carbon-carbon double bond and a blocky or slightly blocky distribution of the double-bond dyads. In addition, the catalysts based on WCl6 and aluminoxane (diisobutylaluminoxane) exhibited a rather high cis stereospecificity in cyclopentene polymerization. ESR and UV-Vis investigations as well as ceriometric determinations performed on WCl6/Bu3iAl, WCl6/Bu2iAlOAlBu2i, WCl6/Me2(allyl)2Si and WCl6/Ph4Sn afforded new structural data concerning the oxidation states of the W atom and the interaction between the catalytic components. These results indicated that (if other parameters, e.g., temperature, time, activators, solvent, are not considered) there exists a direct correlation between the oxidation state of the W species generated in these systems and the polymer microstructure. These data allowed proposals to be advanced concerning the structure of the active species, the mechanism and the stereochemistry of the ring-opening polymerization induced by the above catalysts.
