Double cyclizative polymerization of trienes catalyzed by Pd complexes. Combined ring-forming and chain-walking reactions of the growing end†
Pd complex with a diimine ligand catalyzes polymerization of 1,6,13-heptadecatrienes having functionalized substituents at 4 and 11 positions to produce the polymers containing two functionalized trans-1,2-cyclopentylene groups in every repeating unit. The two neighboring five-membered rings of the polymer are separated by ethylene and pentamethylene spacers alternatingly, suggesting that the chain-walking of the growing polymer end occurs smoothly until formation of the five-membered ring or insertion of a vinyl group of the new monomer into the terminal Pd–CH2 bond. The 1,6,13-heptadecatrienes having the cyclic acetal group at the 4-position and the cyclic acetal, cyclic ester, acyclic ester, or sulfonamide groups at the 11 position undergo smooth polymerization to produce the polymers with Mn > 10 000. The monomer with ester groups at 4-position gives polymers in low yields.