Synthesis of L2Ni(ORF)2 (RF=C(CF3)3) Complexes and their Reactivity in Ethylene Oligomerization

Abstract : A family of L2Ni(ORF)2 (L2: (Cy3PO)24, dcpmS 5, dppf 9, bipyMe210; RF = C(CF3)3) complexes is synthesized via selective substitution of 2 equiv of (DME)NaORF from homoleptic [Ni(ORF)4][Na(DME)]2 complex 1, all characterized by 19F and 1H NMR and SCXRD analyses as well as elemental analyses. These L2Ni(ORF)2 precursors, activated by 2 equiv of PhF → Al(ORF)3, were active in ethylene oligomerization with selectivity toward butenes up to 97% and activities ranging from 10 to 50 kgC2H4·gNi·h–1. Mechanistic investigations, involving experiments with C2H4/C2D4 (1/1) coupled with GC-MS analysis, revealed the formation of a Ni–H fragment in the catalytic process. The L2Ni(ORF)2/2PhF → Al(ORF)3 catalytic system thus dimerizes ethylene through a Cossee–Arlman mechanism.