Polymerization of Higher α-Olefins with a Bis(Phenoxyimine)Ti Complex/i-Bu3Al/Ph3CB(C6F5)4: Formation of Stereo- and Regioirregular High Molecular Weight Polymers with High Efficiency

Abstract

The unique catalytic behavior of a bis(phenoxyimine)Ti complex combined with i-Bu3Al/Ph3CB(C6F5)4 (whose active species is a phenoxyamine Ti complex) is discussed here for use in the polymerization of higher α-olefins (i.e., 1-hexene, 1-octene, 1-decene, and 4-methyl-1-pentene). The catalyst system works as a single-site catalyst and exhibits high activities toward the higher α-olefins that were used in this study. The activities are comparable to or exceed those seen with a common metallocene catalyst, rac-[C2H4-(1-indenyl)2]ZrCl2. The polymerization rate has a zeroth-order dependence on the concentration of the monomer. To our surprise, the system exhibited higher activities toward higher α-olefins that incorporate more sterically encumbered substituents in close proximity to the olefinic moieties (activity order: 4-methyl-1-pentene > 1-decene > 1-octene > 1-hexene). The resultant polymers have very high molecular weights (Mw 846 000−1 450 000), representing some of the highest reported for poly(higher α-olefin)s. Microstructural analyses using 13C NMR spectroscopy revealed that these high molecular weight polymers possess atactic structures with significant regioirregular units (ca. 50 mol %). Therefore, the catalyst system produced stereo- and regioirregular high molecular weight poly(higher α-olefin)s (“ultra-random polymers”) with high efficiency.