Structure-Activity Relationship of Palladium Phosphanesulfonates: Toward Highly Active Palladium-Based Polymerization Catalysts

Palladium phosphanesulfonate [R2P(C6H4-o-SO3)PdMeL] catalysts permit the copolymerization of an exceptional large number of functional olefins with ethylene. However, these catalysts usually have reduced activity. We here have conducted a systematic study on the influence of the phosphane substituent, R, on activity and molecular weight. Phosphanes with strong s-donating character are shown to lead to the most active catalysts. Thus, the catalyst based on phosphane bis-tert-butyl-phosphanyl-benzenesulfonic acid (R=tBu) exhibits unprecedented high activity, rapidly polymerizing ethylene at room temperature to yield a linear polymer of high molecular weight (Mw=116?000 g?mol-1). The influence of the R group on the catalyst ability to incorporate methyl acrylate is also investigated.