POLYMERIZATION OF FUNCTIONALIZED NORBORNENES EMPLOYING MO(CH-T-BU)(NAR)(O-T-BU)2 AS THE INITIATOR

Norbornenes containing esters, cyano, acetate, and related functionalities can be polymerized in a living manner employing Mo(CH-t-Bu)(NAr)(O-t-Bu)2 as the initiator, especially in THF, to give polymers with polydispersities as low as 1.04. Poly(exo-cis-2,3-norbornenediol diacetate) (poly-6), poly(exo-syn-2,7-norbornenediol diacetate) (poly-7), and poly(exo-cis-O,O'-isopropylidene-2,3-norbornendiol) (poly-8) can be hydrolyzed to give polymers containing hydroxyl groups in place of acetates. Poly-6 and poly-7 lose 2 equiv of acetic acid above 300-degrees-C to give black intractable films; the analogous diols lose 2 equiv of water under similar conditions. Addition of exo-cis-2,3-dichloro-endo-cis-2,3-(carbonyldioxy)norbornene (12) to Mo-(CH-t-Bu)(NAr)(O-t-Bu)2yields an isolable square-pyramidal molybdacyclobutane complex, approximately 50% of which loses 12 at room temperature to re-form Mo(CH-t-Bu)(NAr)(O-t-Bu)2. A block copolymer of 5-cyanonorbornene (5) and norbornene (100/100 equiv) was prepared. Living polymers containing molybdenum alkylidene end groups have been characterized by H-1 NMR methods.