Ring Opening Metathesis Polymerization of Cyclic Olefins by PMe ₃ –Supported (Arylimido)Niobium–Alkylidene Catalysts

ABSTRACT Ring opening metathesis polymerization (ROMP) is known as an efficient method for synthesis of functional polymers; metal‐alkylidene (carbene) species play a role as catalysts. (Arylimido)niobium(V)‐alkylidene catalysts display superior capability as the catalysts, and this report summarizes results in ROMP of norbornene, norbornadiene, tetracyclododecene using the catalysts containing fluorinated alkoxide ligand, Nb(CHSiMe 3 )(NAr)[OC(CF 3 ) 3 ](PMe 3 ) 2 [Ar = 2,6‐F 2 C 6 H 3 ( 1 ), C 6 F 5 ( 2 )], and the perhalophenoxide ligands, Nb(CHR)(NAr)(OC 6 F 5 )(PMe 3 ) 2 [R = SiMe 3 , Ar = 2,6 —Cl 2 C 6 H 3 ( 3 ); R = CMe 2 Ph, C 6 F 5 ( 4 )] and Nb(CHSiMe 3 )(NAr)(OC 6 Cl 5 )(PMe 3 ) 2 [Ar = 2,6‐F 2 C 6 H 3 ( 5 ), C 6 F 5 ( 6 )]. Among the perhalophenoxide catalysts ( 3 ‐ 6 ), the pentafluorophenylimido catalysts ( 4 , 6 ) showed rather low catalytic activity compared to the corresponding 2,6‐dihalophenylimido catalysts ( 3 , 5 ), whereas the perfluorinated alkoxide catalysts ( 1 , 2 ) exhibited the opposite trend. The ROMP of low strained cis ‐cyclooctene (COE) using the pentachlorophenoxide catalysts ( 5 and 6 ) proceeded in a controlled manner even at 100°C upon addition of PEt 3 (10 equiv), showing linear correlations between the M n values (in the resultant polymer) and the polymer yields (TON values). The M n values were controlled in the ROMPs of COE using catalysts 5 and 6 at 80°C by additions of allyltrimethylsilane to afford the end‐functionalized oligomers.