Ruthenium ring-opening metathesis polymerization catalysts bearing O-aryloxide-N-heterocyclic carbenes

摘要

A series of o-aryloxide-N-heterocyclic carbene ruthenium complexes 2-4 is synthesized via sequential reactions of the o-hydroxyaryl imidazolium proligands (2-OH-3,5-t~Bu_2C_6H_2)(R)(C_3H_3N_2)~+Br~- (R = Me (1a), iPr (1b), Mes (1c)) with Ag2O and [(C_6HV6)RuCl_2]_2. All of the complexes are characterized by 1~H and (13)~C NMR spectroscopy, high-resolution mass spectrometry (HRMS), and elemental analysis. The molecular structure of 2 is determined by single-crystal X-ray diffraction analysis. The ring-opening metathesis polymerization (ROMP) of norbornene (NBE) with 2-4 is studied. Among them, complex 4 exhibits the highest activity and efficiency toward ROMP of NBE at 85 °C without any cocatalyst, and the resultant polymers have very high molecular weight (>10~6 Da) and narrow molecular weight distributions. This complex can also efficiently catalyze the alternating copolymerization of NBE and cyclooctene. A series of o-aryloxide-NHC Ru-benzene complexes 2-4 is prepared and applied for the ring-opening metathesis polymerization (ROMP) of norbornene (NBE). Among them, complex 4 exhibits the highest activity toward ROMP of NBE at 85 °C without any cocatalyst, and the resultant polymers have very high M_w (>10~6 Da) and narrow molecular weight distributions. This complex can also catalyze the alternating copolymerization of NBE and cyclooctene.