Halogenated Olefins as Chain Transfer Agents in the Synthesis of Telech- elic Polynorbornenes U sing R uthenium Alkylidene C atalysts. C omputa- tional and Experimental Studies
نویسندگان
چکیده
Ring-opening metathesis polymerization (ROMP) of norbornene (NB) and its derivatives N-adamantyl-exoendo-norbornene-5,6-dicarboximide (AdNDI) and N-cyclohexyl-exo-endo-norbornene-5,6-dicarboximide (CyNDI) in the presence of cis-1,4-dichloro-2-butene (2a) and cis-1,2-dichloro-ethylene (2b) as chain transfer agents (CTAs) using a [1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazolilydene] (PCy3)Cl2Ru=CHPh (I) has been studied. Halogenated olefin 2b shows no activity as a CTA when halogenated olefin 2a is readily cross-metathesized with NB and norbornene dicarboximides. The chain transfer reaction pathways during the ROMP of NB to 2b using a (1,3-diphenyl-4,5dihydroimidazol-2-ylidene) (PCy3)Cl2Ru=CHPh (1) have been studied at B3LYP/LACVP* level of theory. The calculations show that 2b is a poor substrate for the metathesis reaction due to the steric effect produced by chlorine atoms directly linked to the double bond. The calculated Gibbs free activation energy of a chain transfer reaction from ring-opened NB to 2b was 25.1 kcal/mol.
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