Cyclopolymerization of Nonconjugated Dienes with a Tridentate Phenoxyamine Hafnium Complex Supported by an sp3-C Donor: Isotactic Enchainment and Diastereoselective cis-Ring Closure

摘要

Cyclopolymerization of nonconjugated dienes produces poly(methylene-1,3-cycloalkanes) and provides a pathway to a number of stereochemically complex polymers. Activation of a diastereomeric mixture of a six-membered metallacycle complex (rac-1) in the presence of 1,5-hexadiene produced poly(methylene-1,3-cyclopentane) (PMCP) with >98 cyclization of the diene monomer. The catalyst was found to cyclopolymerize 1,5-hexadiene with relatively high activity. The microstructure of the PMCP furnished by rac-1 was found to contain a high proportion of cis-cyclopentane rings (sσ=0.70–0.74) and a relatively high isotactic content (aα=0.93–0.96). These are the first cis-enriched isotactic cyclopolymers of 1,5-hexadiene.Cyclopolymerization of 1,6-heptadiene with rac-1/B(C6F5)3 produced poly(methylene-1,3-cyclohexane) containing 97 cis-isotacticrings. This is the first report of this highly isotactic and diastereomerically-pure microstructure.