Tailored molybdenum imido alkylidene N‐heterocyclic carbene complexes as latent catalysts for the polymerization of dicyclopentadiene

Abstract

ABSTRACTThree novel molybdenum imido alkylidene N‐heterocyclic carbene (NHC) pre‐catalysts, that is, Mo(N‐t‐Bu)(1‐(2,6‐diisopropylphenyl)‐3‐isopropyl‐4‐phenyl‐1H‐1,2,3‐triazol‐5‐ylidene)(CHCMe2Ph)(OTf)2 (I1, OTf = CF3SO3), Mo(N‐t‐Bu)(1‐(2,6‐diisopropylphenyl)‐3‐isopropyl‐4‐phenyl‐1H‐1,2,3‐triazol‐5‐ylidene)(CHCMe2Ph)(OTf)(t‐BuO) (I2) and Mo(N‐2,6‐Me2‐C6H3)(1,3,4‐triphenyl‐4,5‐dihydro‐1H‐1,2,4‐triazol‐5‐ylidene)(CHCMe2Ph)(OTf)2 (I3) are presented. Compared to complexes based on imidazol‐2‐ylidenes or imidazolin‐2‐ylidenes, (1‐(2,6‐diisopropylphenyl)‐3‐isopropyl‐4‐phenyl‐1H‐1,2,3‐triazol‐5‐ylidene) used in precatalysts I1 and I2 exerts a comparably strong trans effect to the triflate groups trans to the NHC, while (1,3,4‐triphenyl‐4,5‐dihydro‐1H‐1,2,4‐triazol‐5‐ylidene) used in I3 has a weaker trans effect on the triflate. In combination with a suitable second anionic ligand at molybdenum, that is, OTf, t‐BuO, compounds I1–I3 require higher temperatures to become active and can thus be used as truly room temperature latent pre‐catalysts, even for a highly reactive monomer such as dicyclopentadiene (DCPD). When used as latent precatalysts, I1–I3 offer access to poly‐DCPD with different degrees of cross‐linking and glass‐transition temperatures (Tg). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3028–3033