We wish to communicate here the delineation of a sequential metallocenium-catalyzed ring-opening-'zipping-up' Ziegler polymerization of methylenecyclopropane which yields, in high chemo- and stereoselectivity, a saturated polyspirane having structure B, poly(1,4:2,2-butanetetrayl), as well as some of the interesting structural and thermal properties of this new material. Polymerization of methylenecyclopropane catalyzed by (Me5Cp)2ZrMe+MeB(C6F5)3-2h was carried out in dilute toluene solutions under rigorously anhydrous/anaerobic conditions. At temperatures from -10°C to -30°C, rapid and complete consumption of the monomer is observed by NMR using the monomer:catalyst ratios shown. Interestingly, at room temperature, the reaction pauses before monomer is completely consumed. That this loss of activity is not due to poisoning of the catalyst by adventitious impurities is confirmed by the observation that activity is completely restored on exposure to H2. In summary, these results describe the synthesis of a new polyspirane via the chemo- and stereoselective ring-opening-zipping-up polymerization of methylenecyclopropane catalyzed by a cationic d0 zirconocenium catalyst. Efforts to obtain additional structural and mechanistic information are underway.
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