| Abstract
| - Dimeric titanatranes, Ti2(OR‘)2{[(O-2,4-Me2C6H2-6-CH2)2(μ2-OCH2CH2)]N}2 [R‘ = iPr (1a), tBu (1b)], and monomeric titanatranes, Ti(OR‘)[(O-2,4-tBu2C6H2-6-CH2)2(OCH2CH2)]N (2a,b), have been prepared. The reaction of 1a,b with 2.0 equiv of AlMe3 in toluene gave {TiMe[(O-2,4-Me2C6H2-6-CH2)2(μ2-OCH2CH2)N]}[Me2Al(μ2-OR‘)] (3a,b), in exclusive yields. Ethylene polymerization in octane by 3b took place without additional cocatalyst with moderate catalytic activity, affording high molecular weight polymer with unimodal distribution.
- Syntheses and structural characterizations of various titanatranes containing bis(aryloxo)ethanolamineligands of the type [(O-2,4-R2C6H2-6-CH2)2(OCH2CH2)]N3- (R = Me, tBu) have been explored. Thereaction of [(HO-2,4-Me2C6H2-6-CH2)2(HOCH2CH2)]N with Ti(OR‘)4 in toluene afforded dimerictitanatranes, Ti2(OR‘)2{[(O-2,4-Me2C6H2-6-CH2)2(μ2-OCH2CH2)]N}2 [R‘ = iPr (1a), tBu (1b)], in highyields. Crystallographic analyses of 1a,b indicate that these complexes have a distorted octahedral geometryaround Ti, and the O atom in the alkoxo ligand is coordinated to two Ti atoms. The similar reactions of[(HO-2,4-tBu2C6H2-6-CH2)2(HOCH2CH2)]N with Ti(OR‘)4 afforded the monomeric titanatranes Ti(OR‘)[(O-2,4-tBu2C6H2-6-CH2)2(OCH2CH2)]N (2a,b) in high yields; these complexes have a rather distortedtrigonal bipyramidal structure around Ti consisting of a plane formed by two aryloxo and one alkoxoligand and an N−Ti−O (in OtBu) axis determined by the X-ray crystallographic analyses. The reactionof 1a,b with 2.0 equiv of AlMe3 (1.0 equiv per Ti) in toluene gave the Ti−Me complexes coordinatedto Me2Al(OR‘), {TiMe[(O-2,4-Me2C6H2-6-CH2)2(μ2-OCH2CH2)N]}[Me2Al(μ2-OR‘)] [R‘ = iPr (3a), tBu(3b)], in exclusive yields, and these complexes were identified by 1H and 13C NMR spectra, elementalanalyses, and X-ray crystallography. Complexes 1a and 2b exhibited moderate catalytic activities forethylene polymerization at 100−120 °C in the presence of methylaluminoxane (MAO), and the activityincreased upon the addition of a small amount of AlMe3. Similar catalytic activities were observed byusing 3a,b in the presence of MAO, affording high molecular weight polyethylene with unimodal molecularweight distributions. Ethylene polymerization in octane by 3b took place without additional cocatalyst at120 °C with moderate catalytic activity (94 kg PE/mol Ti·h), affording high molecular weight polymerwith unimodal distribution (Mw = 1.00 × 106, Mw/Mn = 2.58). The result clearly suggests that the cationicspecies formed by cleavage of the Ti−O bonds plays an important role as the active species for thepolymerization.
|
