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<boolean AND>N)Cl]Cl (4, C<boolean AND>N = 3-Methyl-1-picolyimidazol-2-ylidene), [Cp*Ir(C<boolean AND>N)Cl][Cp*IrCl3] (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 H-1 NMR, C-13 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 x 10(5) g PNB (mol Ir) (1)h (1) and 1.70 x 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, H-1 NMR and C-13 NMR spectra, showing it follows the vinyl-addition-type of polymerization.