NNNO-Heteroscorpionate nickel (II) and cobalt (II) complexes for ethylene oligomerization: the unprecedented formation of odd carbon number olefins |
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| Authors: | Sergey V Zubkevich Vladislav A Tuskaev Svetlana Ch Gagieva Anatoliy S Kayda Victor N Khrustalev Alexander A Pavlov Dmitry N Zarubin Boris M Bulychev |
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| Institution: | 1. Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 11, Moscow, 119991 Russia;2. Peoples' Friendship University of Russia (RUDN University), Miklukho-Maklay St., 6, Moscow, 117198 Russian Federation;3. Russian Academy of Sciences, A.N. Nesmeyanov Institute of Organoelement Compounds, Vavilova st. 28, Moscow, 119991 Russia |
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| Abstract: | The unprecedented observation of odd carbon number olefins is reported during nickel- catalyzed ethylene oligomerization. Two complexes based on Co (II) and Ni (II) with novel tetradentate heteroscorpionate ligand have been synthesized and fully characterized. These complexes showed the ability to oligomerize ethylene upon activation with various organoaluminum compounds (Et2AlCl, Et3Al2Cl3, EtAlCl2, MMAO). Ni (II) based catalytic systems were sufficiently more active (up to 1900 kg·mol (Ni)−1·h−1·atm−1) than Co (II) analogs and have been found to be strongly dependent on the activator composition. The use of PPh3 as an additive to catalytic systems resulted in the increase of activity up to 4,150 kg·mol (Ni)−1·h−1·atm−1 and in the alteration of selectivity. All Ni (II) based systems activated with EtAlCl2 produce up to 5 mol. % of odd carbon number olefins; two probable mechanisms for their formation are suggested – metathesis and β-alkyl elimination. |
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| Keywords: | cobalt ethylene oligomerization heteroscorpionate nickel odd carbon number olefins |
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