The position of the sulfur atom in the thienyl group of 6-(thienyl)-2-(imino)pyridine ligands strongly affects the catalytic activity of the corresponding tetrahedral high-spin dihalide CoII complexes in the oligomerization of ethylene to alpha-olefins upon activation with methylaluminoxane (MAO). Complexes with the sulfur atom in the 3-position of the thienyl ring catalyze the selective conversion of ethylene to 1-butene, while catalysts containing thien-2-yl groups give C4-C14 alpha-olefins. In situ EPR experiments showed the occurrence of a spin state changeover with the formation of low-spin CoII species upon activation of the catalyst precursors by MAO. DFT calculations suggest that only thien-2-yl rings allow for the coordination of the sulfur atom to the cobalt center in the MAO-activated systems.
Electronic Influence of the Thienyl Sulfur Atom on the Oligomerization of Ethylene by 6-(Thienyl)-2-(imino)pyridine Cobalt(II) Catalysis / Bianchini C; Gatteschi D; Giambastiani G; Rios Guerrero I; Ienco A; Laschi F; Mealli C; Meli A; Sorace L; Toti A; Vizza F. - In: ORGANOMETALLICS. - ISSN 0276-7333. - STAMPA. - 26:(2007), pp. 726-739. [10.1021/om0609665]
Electronic Influence of the Thienyl Sulfur Atom on the Oligomerization of Ethylene by 6-(Thienyl)-2-(imino)pyridine Cobalt(II) Catalysis
Giambastiani G;Sorace L;
2007
Abstract
The position of the sulfur atom in the thienyl group of 6-(thienyl)-2-(imino)pyridine ligands strongly affects the catalytic activity of the corresponding tetrahedral high-spin dihalide CoII complexes in the oligomerization of ethylene to alpha-olefins upon activation with methylaluminoxane (MAO). Complexes with the sulfur atom in the 3-position of the thienyl ring catalyze the selective conversion of ethylene to 1-butene, while catalysts containing thien-2-yl groups give C4-C14 alpha-olefins. In situ EPR experiments showed the occurrence of a spin state changeover with the formation of low-spin CoII species upon activation of the catalyst precursors by MAO. DFT calculations suggest that only thien-2-yl rings allow for the coordination of the sulfur atom to the cobalt center in the MAO-activated systems.File | Dimensione | Formato | |
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