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

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∗IrCl3] (5), [Cp∗Ir(C-N)Cl]Cl (6, C-N = 3-Methyl-1-pyridylimidazol-2-ylidene) and [Cp∗Ir(L)Cl2] (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 × 105 g PNB (mol Ir)−1 h−1 and 1.70 × 106 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.