Synthesis of functional and hyperbranched ethylene oligomers using unsymmetrical α-diimine palladium catalysts

Abstract

A series of unsymmetrical α-diimine palladium complexes bearing low steric crowdedness on one side and bulky substituents on the other side were prepared and characterized. Activated with sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate, these α-diimine Pd(II) complexes were used to catalyze ethylene oligomerization and cooligomerization with polar monomers including methyl acrylate (MA), acrylic acid (AA) and vinyltriethoxysilane (VTEoS). In ethylene oligomerization, the hyperbranched oil products were obtained with high activities (14.2–27.0 × 103 g mol−1 h−1). The remote substituent of bulky diarylmethyl moiety showed a significant effect on catalyst activity, while exhibit little variation on the molecular weight of ethylene oligomers. In ethylene-polar monomer cooligomerization, functional and hyperbranched oils were produced and polar monomer incorporations can be tuned by the perturbations of the remote substituent.