RING-OPENING METATHESIS POLYMERIZATION OF ETHYL)-2-AZABICYCLO[2.2.1]HEPT-5-ENE-3-CARBOXYLATE

Enantiomerically pure (1) and racemic (2) ethyl)-2-azabicyclo[2.2.1]he pt-5-ene-3-carboxylate were found to undergo ring opening metathesis p olymerization reactions employing molybdenum alkylidene initiators of the type Mo(CH-t-Bu)(NAr)(OR)(2) (Ar = 2,6-C6H3-i-Pr-2; R = C(CH3)(3); C(CH3)(2)CF3; CCH3(CF3)(2)) in various aprotic solvents. Chain transf er by terminal olefins such as 1-octene leads to a decrease in molecul ar weights which can be correlated to the amount of chain transfer age nt added. In this way oligomers can be prepared with lower initiator c onsumption. The presence of alkylidene signals in the H-1-NMR spectra and the possibility of chain transfer by acyclic olefins strongly conf irm the assumption of a molybdenum alkylidene intermediate as a propag ating species in a living polymerization. From the dramatic effect the presence of even small amounts of quinuclidine added as complexing ag ent has on the polymerization rate of (1) employing (III), we assume, that there is hardly any complexion of the initiator by the nitrogen o f the monomer, otherwise the polymerization of (1) should be very slow or even impossible. The stereochemistry of the polymers can be correl ated with the electron withdrawing effect of the initiator's alkoxide ligands. Fluorinated ligands at the initiator lead to polymers with in creasing cis-vinylene content. There is no significant effect of the s olvent's polarity on the stereochemistry of the resulting polymers.