Key Words:OLEFIN POLYMERIZATION; MONO(SALICYLALDIMINATO) TITANIUM; BINUCLEAR CATALYSTS; MOLECULAR-WEIGHT; COPOLYMERIZATION; COMPLEXES; ENCHAINMENT; METAL; LIGANDS
Abstract:Dinuclear titanium complexes <bold>syn-Ti-2</bold> and <bold>anti-Ti2</bold> bearing anthracene-bridged bisphenoxyimine ligands (<bold>syn-L</bold> and <bold>anti-L</bold>) have been prepared and characterized by NMR and elemental analyses. The molecular structure of <bold>syn-Ti2</bold> was defined by X-ray diffraction, revealing a separation of 7.183 angstrom between the two Ti centers. The mononuclear complex [(2,6-Pr-i(2)-C6H3N = CH-C6H2-3,5-Bu-i-2-O)TiCl3(THF)] (<bold>Ti-1</bold>) was also prepared for control experiments. In the presence of MAO as a cocatalyst, <bold>syn-Ti-2</bold> and <bold>anti-Ti-2</bold> were active toward ethylene homopolymerization but had distinct catalytic properties. The complex <bold>syn-Ti-2</bold> with a shorter metalmetal separation exhibited higher activity and produced polymers with higher molecular weights, in comparison to <bold>anti-Ti-2</bold>, having a longer metalmetal separation, and the mononuclear catalyst control <bold>Ti1</bold> under identical conditions. More importantly, the complex <bold>syn-Ti-2</bold> exhibited excellent thermal stability and thus the a greater activity can be obtained at 100 degrees C, which is a preferred temperature for industrial operations. For ethylene/1-hexene copolymerization, the activity, Mw, and incorporation of 1-hexene by <bold>syn-Ti-2</bold> were 2.3x, 3.2x, and 6.0x those of <bold>anti-Ti-2</bold> under identical conditions.
Volume:39
Issue:17
Translation or Not:no