Electronic Influence of the Thienyl Sulfur Atom on the Oligomerization of Ethylene by Cobalt(II) 6-(Thienyl)-2-(imino)pyridine Catalysis
作者:Claudio Bianchini、Dante Gatteschi、Giuliano Giambastiani、Itzel Guerrero Rios、Andrea Ienco、Franco Laschi、Carlo Mealli、Andrea Meli、Lorenzo Sorace、Alessandro Toti、Francesco Vizza
DOI:10.1021/om0609665
日期:2007.1.1
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 Co-II 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 C-4-C-14 alpha-olefins. In situ EPR experiments showed the occurrence of a spin state changeover with the formation of low-spin Co-II 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.