Repetitive Ethylene Insertion into the Pd–OAc Bond: Synthesis of Heterotelechelic Polyethylene and Effective Copolymerization of Ethylene with Vinyl or Allyl Acetate

Palladium-catalyzed oxidative functionalization of ethylene, exemplified by Wacker oxidation, has been fundamental in organic chemistry. Despite the potentially versatile reactivity of Pd-alkyl intermediates formed after oxypalladation of ethylene, explorations of their subsequent reactions are limited due to the rapid β-H elimination. Here we found that the palladium acetate complex bearing a phosphine-sulfonate ligand containing a 2,5-dichlorothiophene-3,4-diyl backbone enables multiple ethylene insertion into the Pd-OAc bond by suppressing the competing β-H elimination. This reactivity provides access to heterotelechelic polyethylene and facilitates the copolymerization of ethylene with vinyl acetate or allyl acetate.