Synthesis, Structures, and Norbornene Polymerization Behavior of o-Aryloxide-Substituted NHC-Ligated σ, π-Cycloalkenyl Palladium Complexes

Treatment of the pro-ligand (2-OH-3,5-(Bu2C6H2)-Bu-t)(Mes)(C3H3N2)Br+ (2a) with di[mu-chloro-2 eta(2),5 eta(1)-(6-methoxy-endo-bicyclo[2.2.1]-hept-2-enyl)palladium(II)] (1a) and K(2)CO3 in dioxane, or reaction of the pro-ligand 2a subsequently with (BuLi)-Bu-n and 1a in THF afforded the o-aryloxide-substituted NHC-ligated s, p-cycloalkenyl palladium complex 3. Similarly, treatment of the pro-ligands (2-OH-3,5-tBu(2)C(6)H(2))(R)(C3H3N2)Br+ [R = Mes (2a), Me (2b), iPr (2c), Ph (2d)] with bis[mu-chloro-1 eta(2),5 eta(1)-(6-ethoxy-exo-5,6-dihydrodicyclopentadienyl)palladium(II)] (1b) and K2CO3 in dioxane afforded the desired products 49. All these complexes were fully characterized by H-1 and C-13 NMR, high-resolution mass spectrometry (HRMS), and elemental analysis. Single-crystal X-ray diffraction analysis results further confirmed the molecular structures of 36. With methylaluminoxane (MAO) as cocatalyst, these complexes showed excellent catalytic activities up to 10(7) g of PNB (mol of Pd) (-1) h(-1) in the addition polymerization of norbornene.