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

Complexes [Pd(eta(1), eta(2)-5-OMe-(CH12)-H-8)(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(eta(1),eta(2)-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 eta(1),eta(2)-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 la were investigated by X-ray single crystal studies. F-19,H-1-HOESY NMR experiments carried out in methylene chloride-d(2) 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. (C) 2003 Elsevier B.V. All rights reserved.