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

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 alpha-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 alpha-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 alpha-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 (M-w 846 000- 1 450 000), representing some of the highest reported for poly( higher alpha-olefin)s. Microstructural analyses using C-13 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 alpha-olefin)s ("ultra-random polymers") with high efficiency.