Several families of late transition metal (Fe, Co, Ni, Pd) complexes supported by imine-based multidentate ligands have been explored as catalysts for olefin homo- and copolymerization. A key feature of these systems is that the ortho-substituents on the N-aryl units strongly influence the rates of chain growth, chain walking, and chain transfer, and hence the microstructure of the polymer. This talk will focus on the chemistry of imine-based ligands that contain chiral (1R,2S,5R)-menthyl units as ortho substituents on the N-aryl groups. The menthyl substituents were chosen to provide both proximal and distal steric bulk around the metal center. We synthesized a C2-symmetric dimenthyl-substituted α-diimine ligand, bis[(o-menthyl-p-tolyl)imino]acenaphthene (NNmenthyl) and the corresponding (NNmenthyl)Ni(acac)+B(C6F5)4- and (NNmenthyl)PdMeCl complexes (see Figure), and characterized their conformations by NMR in solution and X-ray diffraction in the solid state. These studies revealed an unexpected preference for a C1-symmetric syn-atropisomeric conformation in which both menthyl groups are positioned on the same face of the (N=C-C=N)M square plane. The application of (NNmenthyl)Ni and (NNmenthyl)Pd complexes in olefin polymerization will be discussed.

Application of chiral terpenyl groups in imine-type ligand design for olefin polymerization catalysis

251st National Meeting (2016)

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