Synthesis and catalytic activity of neutral salicylaldiminato nickel(II) complexes bearing a single N-heterocyclic carbene ligand

Neutral salicylaldiminato Ni(II) complexes bearing a single N-heterocyclic carbene (NHC) ligand 3,5-^tBu₂-2-(O)C₆H₂CHNAr]Ni(C{RNCHCHNⁱPr})Ph Ar = 2,6-ⁱPr₂C₆H₃, R = Bn (1); Ar = 2,6-ⁱPr₂C₆H₃, R = ⁱPr (2)], have been synthesized via a one-pot procedure in high yield. The X-ray structure analysis reveals that both of 1 and 2 adopt distorted square-planar coordination geometry and NHC carbon (C_carbene) is trans to the ketimine nitrogen. Preliminary study indicates that complex 1 is inert toward the insertion of ethylene, however, it can catalyze the dimerization of ethylene in the presence of modified methylaluminoxane (MMAO) with a moderate activity of 3.05 × 10⁴ g(mol Ni)⁻¹ h ⁻¹ atm⁻¹ in a highly selective fashion.