Synthesis, Structures, and Norbornene Polymerization Behavior of Bis(aryloxide-N-heterocyclic carbene) Nickel Complexes

Treatment of the o-hydroxyaryl imidazolinium proligands (2-OH-3,5-(Bu2C6H2)-Bu-t)(R)(C3H3N2)Br-+(-) [R = Pr-i (1a), Bu-t (1b), Ph (1c), Mes (1d)] with NiL2Cl2 (L = PPh3, Py) or Ni(OAc)(2)center dot 4H(2)O afforded the corresponding cis bis(aryloxide-NHC) nickel complexes 2-5. Notably, the products were independent from the pro-ligands/Ni ratios. The same complexes were obtained with the pro-ligands/Ni ratio of 1:1 or 2:1. All the complexes were characterized by H-1 and C-13 NMR, high-resolution mass spectrometry (HRMS), and elemental analysis. The molecular structures of the aryloxide-NHC-ligated nickel complexes 2-5 were determined by single-crystal X-ray diffraction analysis. With methylaluminoxane (MAO) as cocatalyst, the nickel complexes showed moderate catalytic activities (10(6) g of PNB (mol of Ni)(-1) h(-1)) in the addition polymerization of norbomene.