Ring-Opening Metathesis Polymerization of (+)- and (.+-.)-endo,exo-5,6-Dimethylbicyclo[2.2.1]hept-2-ene by Mo(CH-t-Bu)(N-2,6-C6H3-i-Pr2)(OR)2

Abstract

Abstract : Ring-opened polymers of (+)- and (-)-endo,exo-5,6-dimethylbicyclo2.2. 1hept-2-ene (1) having cis double bond contents between 5 and 85% were prepared using Mo(CH-t-Bu)(NAr)(OR)2 (Ar = 2,6-C6H3-i-Pr2; OR = OCMe3, OCMe2(CF3), OCMe(CF3)2) complexes as initiators. The cis content of the polymers increased in proportion to the electron-withdrawing power of the alkoxide ligands. 13C NMR spectra (125 MHz) of these polymers were interpreted in terms of the various possible types of dyad structure: XX, XN (NX), NN, where X and N refer to substituents derived from exo and endo methyl groups, m and r refer to the meso (isotactic) or racemic (syndiotactic) configuration of adjacent cyclopentane rings in the chain, and tt, tc, (ct), and cc refer to the cis/trans double bond sequences. High cis polymer made from 98% (+)-l contained 78% m dyads and had more than twice the optical rotatory power and a higher Tg (85 deg C) compared to a high trans polymer (48% m dyads; Tg = 55 deg C).