Ring-Opening Metathesis Polymerization via Ruthenium Complexes of Chelating Diphosphines

High activity and low polymer polydispersity are found in ring-opening metathesis polymerization (ROMP) of norbornene by ruthenium complexes containing chelating diphosphine ligands. Treatment of compounds with general formula RuCl 2 (PP)(PPh 3 ) (PP = dppb ( 3b ), binap ( 3c ), dcypb ( 3d )) or [RuCl 2 (PP)] 2 (PP = dppb ( 4b )) with PhCHN 2 generates carbene complexes of the type RuCl 2 (PP)(CHPh), which exhibit high ROMP activity without halide or phosphine abstraction. Investigations into the role of dissociated PPh 3 have shown that free phosphine acts as a poison, dramatically retarding the rate of polymerization via 3 relative to catalysts derived from 4 .