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Updated: Jun 16, 2026

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions
Published on: July 30, 2017
NHC-Supported (Arylimido)niobium(V)-Alkylidene Catalysts Exhibiting Exceptionally High Catalytic Activities for ROMPs
Ploychompoo Loekukot1, Ryota Ogawa1, Kanchana Chatchaipaiboon1
1Department of Chemistry, Tokyo Metropolitan University, 1-1 minami Osawa, Hachioji, Tokyo 192-0397, Japan.
None:
The NHC-supported (arylimido)-niobium-(V)-alkylidene catalysts containing perhalophenoxide ligands, especially Nb-(CHR)-(NC6F5)-(OC6X5)-(NHC)-(PMe3) [R = SiMe3 or CMe2Ph; X = Cl, Br; NHC = 1,3-bis-(2,4,6-trimethylphenyl)-imidazol-2-ylidene], display remarkable catalytic activities for ring-opening metathesis polymerization (ROMP) of norbornene (NBE), affording ultrahigh molar mass polymers with unimodal molecular weight distributions (M n = 2.02-3.84 × 106). In particular, the ROMP by Nb-(CHSiMe3)-(NC6F5)-(OC6Cl5)-(NHC)-(PMe3) reached completion within 5 s at 25 °C with a turnover frequency (TOF) of >4260 s-1. The ROMP by Nb-(CHSiMe3)-(N-2,6-F2C6H3)-[OC-(CF3)3]-(NHC) gave the cis-syndiotactic polymers, and the polymerization proceeded in a controlled manner without catalyst decomposition.
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