Synthesis, molecular structure and norbornene polymerization behavior of three-coordinate nickel(i) complexes with chelating anilido-imine ligands

Abstract

Reaction of lithium salts of anilido-imine ligands bearing bulky substituentes on the nitrogen donor atoms with trans-chloro(phenyl)bis(triphenylphosphane)nickel(II) results in the formation of two rare three-coordinate nickel(I) complexes [(Ar₁NCHC₆H₄NAr₂)Ni(I)PPh₃] (1: Ar₁ = Ar₂ = 2,6-i-Pr₂C₆H₃; 2: Ar₁ = 2,6-Me₂C₆H₃, Ar₂ = 2,6-i-Pr₂C₆H₃). The molecular structures of complexes 1 and 2 have been confirmed by single crystal X-ray analyses. These two complexes exhibit paramagnetic properties as measured by their EPR and ¹H NMR spectra. After being activated with methylaluminoxane (MAO) these complexes could polymerize norbornene to afford addition-type polynorbornene (PNB) with high molecular weight M_w (10⁶ g mol⁻¹), catalytic activities being high, up to 2.82 × 10⁷ g_PNB mol⁻¹_Ni h⁻¹.