Synthesis and characterization of (pyrazolylphosphinite)nickel(II) and palladium(II) complexes and their catalytic activity towards olefin oligomerization

M.Sc. (Chemistry)Abstract: This thesis contributes to the search towards the development of new nickel(II) complexes towards olefin transformation catalysis. Compounds L1-L3 (2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyldiphenylphosphinite (L1), 2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)ethyldiphenylphosphinite (L2), 2-(3,5-diphenyl-1H-pyrazol-1-yl)ethyldiphenylphosphinite (L3) were prepared using the synthetic routes reported in literature. These compounds were characterized using 1H NMR, 31P{1H}NMR and 13C{1H}NMR spectroscopy. Treatment of L1-L3 with [NiCl2(CH3OCH2)2] or [NiBr2(CH3OCH2)2] under appropriate reaction conditions resulted in the formation of six new nickel(II) compounds (1–6). These nickel complexes, due to their paramagnetic nature, failed to give satisfactory NMR signals. The nickel complexes were therefore characterized using elemental analysis, mass spectrometry, infra-red spectroscopy and magnetic susceptibility measurements. Additionally, these new nickel(II) complexes catalyzed the oligomerization of ethylene in the presence of ethylaluminium dichloride co-catalyst, to produce butenes, hexenes, octenes and higher carbon chain ethylene oligomers with very little Friedel-Crafts alkylation products. The catalytic products were analyzed using gas chromatography (GC), gas chromatography–mass spectrometry (GC-MS) and atmospheric pressure chemical ionization (APCI) mass spectroscopy. Compounds L1-L3 were further treated with [PdCl(CH3)(COD)] and [PdCl2(NCCH3)2] using literature protocols. This resulted in the formation of six palladium complexes 7-12. Compound 7 is known but compounds 8-12 were new. All the palladium compounds were characterized using 1H NMR, 31P{1H}NMR, 13C{1H}NMR spectroscopy and in selected cases..