Novel hemi-labile pyridyl-imine palladium complexes: Synthesis, molecular structures and reactions with ethylene

Abstract

Ligands (2-pyridyl-2-furylmethyl)imine, ( L1), (2-pyridyl-2-thiophenemethyl)imine ( L2), and (2-pyridyl-2-thiopheneethyl)imine ( L3) were synthesized by condensation reactions and obtained in good yields. Reactions of L1– L3 with either [PdClMe(cod)] or [PdCl 2(cod)] gave the corresponding monometallic palladium(II) complexes 1– 5 in very good yields. Molecular structures of complexes 1, 4 and 5 indicated that the ligands are bidentate and coordinate to the palladium metal through the imine and pyridine nitrogen atoms. When complexes 3– 5 were treated with NaBAr 4, cationic species, 3a, 4a, and 5a were produced which catalyzed polymerization of ethylene though with very low activities. 1H NMR spectroscopy studies showed that these cationic species were very stable in solution. DFT calculations showed high ethylene coordination barriers to the cationic species 3a, 4a and 5a.