Abstract
New (pyrazolyl)-(phosphinoyl)pyridine ligands 2-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-6-((diphenylphosphinoyl)methyl)pyridine (L1b) and 2-((3,5-diphenyl-1H-pyrazol-1-yl)methyl)-6-((diphenyl-phosphinoyl)methyl)pyridine (L2b) were synthesized in high yields. Reactions of L1b and L2b with Fe(II), Co(II) and Ni(II) salts afforded complexes [NiCl2(L1b)] (1), [NiBr2(L1b)] (2), [CoCl2(L1b)] (3), [FeCl2(L1b)] (4), [NiBr2(L2b)] (5), and [CoCl2(L2b)] (6) in good yields. The compounds were characterized by NMR spectroscopy, mass spectrometry and elemental analyses. Molecular structures of complexes 1, 5 and 6 were confirmed by single crystal X-ray crystallography to contain one tridentate bound N boolean AND N boolean AND O L1b and L2b ligands. Complexes 1-6 formed active catalysts in ethylene oligomerization reactions upon activation with EtAlCl2, methylaluminoxane (MAO) or trimethylaluminium (AlMe3) as co-catalyst to produce C-4 as the major product as well as C-6 and C-8 oligomers. The nature of solvent and co-catalyst, significantly affected both the activities and product compositions of the resultant catalysts. (C) 2015 Elsevier B.V. All rights reserved.