Functionalized N-heterocyclic carbene iridium complexes: Synthesis, structure and addition polymerization of norbornene

Abstract

Picolyl, pyridine, and methyl functionalized N-heterocyclic carbene iridium complexes [Cp ∗Ir(C^N)Cl]Cl ( 4, C^N = 3-Methyl-1-picolyimidazol-2-ylidene), [Cp ∗Ir(C^N)Cl][Cp ∗IrCl 3] ( 5), [Cp ∗Ir(C-N)Cl]Cl ( 6, C-N = 3-Methyl-1-pyridylimidazol-2-ylidene) and [Cp ∗Ir(L)Cl 2] ( 7, L = 1,3-dimethylimidazol-2-ylidene) have been synthesized by transmetallation from Ag(I) carbene species, and characterized by 1H NMR, 13C NMR spectra and elemental analyses. The molecular structures of 5–7 have been confirmed by X-ray single-crystal analyses. The iridium carbene complexes 4 and 6 show moderate catalytic activities (3.03 × 10 5 g PNB (mol Ir) −1 h −1 and 1.70 × 10 6 g PNB (mol Ir) −1 h −1) for the addition polymerization of norbornene in the presence of methylaluminoxane (MAO) as co-catalyst. The produced polynorbornene have been characterized by IR, 1H NMR and 13C NMR spectra, showing it follows the vinyl-addition-type of polymerization.