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

A family of L2Ni(ORF)(2) (L-2: (Cy3PO)(2) 4, dcpmS 5, dppf 9, bipyMe(2) 10; R-F = 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 F-19 and H-1 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 kg(C2H4).g(Ni).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.