Chain-walking polymerization of 3-heptene with phenyl substituted α-diimine nickel catalysts

The first example of a 3-alkene polymerization has been successfully achieved with 3-heptene in the presence of phenyl-substituted alpha-diimine nickel precatalysts activated by dMMAO, and compared with the corresponding linear alkenes, i.e., 1-pentene, 2-hexene and 4-octene polymerizations. The microstructures of the produced poly (3-heptene), which consists of ethyl, propyl and butyl branches indicated the 3,4- and 4,3-insertion, followed by chain-walking, with incorporation of a small fraction of long methylene sequences of 1,7-enchainment via monomer-isomerization. Late-transition metal catalyzed polymerization reactions of internal alkenes to synthesize novel polyolefin materials are highly important and also highly challenging. Upon activation with dried modified methyl-aluminoxane (dMMAO), the first example of a 3-alkene polymerization has been successfully achieved for 3-heptene catalyzed by phenyl-substituted a-diimine nickel complexes in comparison, and compared with the polymerizations of the corresponding linear alkenes, i.e., 1-pentene, 2-hexene and 4-octene. The results indicate that the polymerization of 3-heptene was achieved via chain-walking to generate branched amorphous polymers with glass transition temperature of ca. - 68 degrees C. The microstructures of the produced poly(3-heptene) indicated the 3,4- and 4,3-insertion followed by chain-walking, the latter being predominant. The NMR analyses of the polymers showed that the obtained poly(3-heptene) possessed ethyl, propyl and butyl branches and a small amount of the long methylene sequence of 1,7-enchainment via monomer-isomerization. The branches structures were significantly dependent on the polymerization temperature, and the content of propyl branches derived from 3,4-insertion decreased with an increase in the polymerization temperature.