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

We report here the polymerization 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 derivatives of two polymers were determined 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 polymerized 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.