Syntheses, Structures, and Catalytic Ethylene Oligomerization Behaviors of Bis(phosphanyl)aminenickel(II) Complexes Containing N ‐Functionalized Pendant Groups

Several N-functionalized bis(phosphanyl)amine ligands respectively containing benzyl, furfuryl, thiophene-2-methyl, thiophene-2-ethyl, and 2-picolyl groups (1a–e) were synthesized and characterized. The ligands reacted with (DME)NiBr2 in CH2Cl2 to give their corresponding nickel complexes [Ph2PN(R)PPh2NiBr2] [R = CH2C6H5 (2a), CH2C4H3O (2b), CH2C4H3S (2c), CH2C5H4N (2d), and CH2CH2C4H3S (2e)]. The structures of these complexes were established by single-crystal X-ray crystallography. All these nickel complexes were highly active towards ethylene oligomerization in the presence of methylaluminoxane or Et2AlCl, producing a high content of butene (C4). Especially for 2e, which contains a thiophene-2-ethyl pendant group, the oligomerization products obtained at –40 °C contained 95.9 mol-% C4 fraction with 100 mol-% 1-butene. Over 50 °C, however, these nickel complexes underwent Friedel–Crafts alkylation of toluene with ethylene and the olefin oligomers.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)