Nickel and palladium complexes with fluorinated alkyl substituted α-diimine ligands for living/controlled olefin polymerization
Abstract
A series of six nickel and two palladium novel complexes bearing α-diimine ligands with fluorinated alkyl substituents in para-aryl positions was prepared. Two nickel complexes were structurally characterized by X-ray diffraction.
Upon activation by methylaluminoxane or borate, the complexes were tested in ethene, propene, and hex-1-ene polymerization using toluene and chlorobenzene. Propene and hex-1-ene polymerization initiated by nickel complexes and ethene polymerization initiated by palladium complexes showed living/controlled character and yielded high molar mass polyolefins with narrow molar mass dispersity (D < 1.2).
The effect of fluoroalkyl substituents on catalyst activity, thermal stability and chain-walking is only minor. The branching density of polyolefins can be regulated more efficiently by the variation of ortho-aryl and backbone substituents of α-diimine ligands.
The topology of polyethylenes prepared by palladium complexes at low ethene pressure is dendritic as shown by Mark-Houwink plots and g' values obtained from SEC with viscometric detection. The solubility of most of the complexes in fluorinated solvents is limited with the exception of palladium methyl chloride derivatives which suggest the promising method for further design of catalysts suitable for interphase polymerization.