Search

Abstract: A series of cobalt (II) complexes ligated by 2-(2-benzoxazolyl)-6-(1-(arylimino)ethyl)pyridines was synthesized and characterized by FT-IR spectroscopic and elemental analysis. The molecular structures of Co1 (Ar=2,6-Me2C6H3), Co2 (Ar=2,6-Et2C6H3) and Co7 (Ar=2,6-Br2C6H3) were determined by single-crystal X-ray diffraction. Compounds Co1 and Co2 display a distorted trigonal-bipyramidal geometry, whereas complex Co7 is a distorted square-pyramid. Upon activation with methylaluminoxane (MAO), all cobalt complexes showed reactivity towards ethylene. There was however an unexpected temperature dependence; whereas, at room temperature oligomerization was observed, giving 1-alkenes with high selectivities, at elevated temperatures polyethylene was produced. This unusual catalytic behavior of the new complexes was investigated in detail under various reaction parameters. [Copyright &y& Elsevier]

Abstract: A series of 2-(1H-benzo[d]imidazol-2-yl)-N-benzylidenequinolin-8-amines was synthesized and characterized. They are stable as solids while displaying a tendency to decompose in solution. On reaction with NiCl2, different coordination pattern sets of L·NiCl2 or [L2Ni]2+·2Cl− are obtainable in THF or ethanol. When activated by Et2AlCl, the complexes L·NiCl2 exhibit good to high catalytic activities and selectivities for 1-C4 in ethylene oligomerization, while the complexes [L2Ni]2+·2Cl− hardly showed any activity, which is attributable to nickel coordination by two ligands barring interaction of ethylene with the metal center. [Copyright &y& Elsevier]

Abstract: A series of tridentate NˆNˆN iron(II) and cobalt(II) complexes containing N-((pyridin-2-yl)methylene)-quinolin-8-amine derivatives were synthesized and characterized by elemental and spectroscopic analyses. The molecular structure of 1a was confirmed by X-ray diffraction analyses. On treatment with modified methylaluminoxane, these metal complexes exhibited good catalytic activities up to 2.8×106 gmol−1(Fe)h−1 for ethylene oligomerization, and butenes were the major products with nice selectivity for 1-C4. The steric and electronic effects on catalytic activities of metal complexes were carefully investigated as well as the influence of various reaction parameters. In the catalytic system, Fe(II) complexes performed better catalytic activities than their Co(II) analogues. With ligands having bulky substituents, the better catalytic activity was observed in catalytic system of Fe(II) complex, however, the lower catalytic activity was obtained in catalytic system of Co(II) complexes. [Copyright &y& Elsevier]