HighlySelective Molybdenum ONO Pincer Complex Initiatesthe Living Ring-Opening Metathesis Polymerization of Strained Alkyneswith Exceptionally Low Polydispersity Indices

摘要

The pseudo-octahedral molybdenum benzylidyne complex [TolC≡Mo(ONO)(OR)]>·KOR (R = CCH3(CF3)2) >1, featuring a stabilizing ONO pincer ligand, initiates the controlled living polymerization of strained dibenzocyclooctynes at T > 60 °C to give high molecular weight polymers with exceptionally low polydispersities (PDI ∼ 1.02). Kinetic analyses reveal that the growing polymer chain attached to the propagating catalyst efficiently limits the rate of propagation with respect to the rate of initiation (kp/ki ∼ 10^–3). The reversible coordination of KOCCH3(CF3)2 to the propagating catalyst prevents undesired chain-termination and -transfer processes. The ring-opening alkyne metathesis polymerization with >1 has all the characteristics of a living polymerization and enables, for the first time, the controlled synthesis of amphiphilic block copolymers via ROAMP.