Cationic olefin Pd(II) complexes bearing α-iminoketone N,O-ligands: synthesis, intramolecular and interionic characterization and reactivity with olefins and alkynes

Complexes [Pd(η1, η2-5-OMe–C8H12)(N,O)]BF4 (N,O=2,6-(i-Pr)2(C6H3)NC(Ph)–C(Ph)O, 1; 2,6-(i-Pr)2(C6H3)NC(Me)–C(Ph)O, 2; 2-benzoylpyridine, 3) were synthesized by the reactions of [Pd(η1,η2-5-OMe–C8H12)Cl]2 with the suitable N,O-ligand. They were tested as catalysts for olefin or alkyne polymerizations. During such reactions 1–3 quantitatively transformed into their η1,η2-1-OMe–C8H12 isomers (1a–3a). The same isomerization occurred in methylene chloride, even in the absence of olefins or alkynes, with a much slower rate. All complexes were fully characterized in solution by multinuclear and multidimensional low temperature NMR spectroscopy. The solid state structures of complexes 1 and 1a were investigated by X-ray single crystal studies. 19F, 1H-HOESY NMR experiments carried out in methylene chloride-d2 at 217 K indicated that the anion prefers to locate on the side of N,O-ligand shifted toward the O-arm in 1–1a and 2–2a while it approaches the N-arm in 3 and 3a compounds.