Stereospecific Ring-Opening Metathesis Polymerization (ROMP) of Norbornene and Tetracyclododecene by Mo and W Initiators

We report the synthesis of >98% <i>cis</i>,<i>isotactic</i> and <i>cis</i>,<i>syndiotactic</i> polynorbornene (poly­(NBE)) and poly­(<i>endo</i>,<i>anti</i>-tetracyclododecene) (poly­(TCD)). <i>Cis</i>,<i>isotactic</i> poly­(NBE) and poly­(TCD) were prepared employing Mo-based biphenolate imido alkylidene initiators, Mo­(NR)­(CHCMe₂Ph)­(Biphen) (Biphen = e.g., 3,3′-(<i>t</i>-Bu)₂-5,5′-6,6′-(CH₃)₄-1,1′-biphenyl-2,2′-diolate), while <i>cis</i>,<i>syndiotactic</i> poly­(NBE) and poly­(TCD) were prepared employing W-based imido or oxo monoaryloxide pyrrolide (MAP) initiators, W­(X)­(CHR′)­(Pyrrolide)­(OTer) (X = NR or O; OTer = a 2,6-terphenoxide). Addition of 1-hexene or coordinating solvents such as THF do not decrease the stereospecificity of the polymerization. <i>Cis</i>,<i>iso</i> and <i>cis</i>,<i>syndio</i> dyads can be distinguished through examination of ¹H and ¹³C NMR spectra of the two polymers in a mixture. The polymers were hydrogenated to give <i>isotactic</i> and <i>syndiotactic</i> H-poly­(NBE) and H-poly­(TCD)