Stereospecific Ring-Opening Metathesis Polymerization of Norbornadienes Employing Tungsten Oxo Alkylidene Initiators.

We report here the polymn. of several 7-isopropylidene-2,3-disubstituted norbornadienes, 7-oxa-2,3-dicarboalkoxynorbornadienes, and 11-oxa-benzonorbornadienes with a single tungsten oxo alkylidene catalyst, W(O)(CH-t-Bu)(OHMT)(Me2Pyr) (OHMT = 2,6-dimesitylphenoxide; Me2Pyr = 2,5-dimethylpyrrolide) to give cis, stereoregular polymers. The tacticities of the menthyl ester derivs. of two polymers were detd. for two types. For poly(7-isopropylidene-2,3-dicarbomenthoxynorbornadiene) the structure was shown to be cis, isotactic, while for poly(7-oxa-2,3-dicarbomenthoxynorbornadiene) the structure was shown to be cis, syndiotactic. A bis-trifluoromethyl-7-isopropylidene norbornadiene was not polymd. stereoregularly with W(O)(CHCMe2Ph)(Me2Pyr)(OHMT) alone, but a cis, stereoregular polymer was formed in the presence of 1 equiv of B(C6F5)3. [on SciFinder(R)]