Abstract
A series of ansa-silylene(fluorenyl)(amido) titanium complexes (1a–1c, 2a, and 2b) bearing various substituents on the amido and fluorenyl ligands are synthesized and characterized by elemental analysis, 1H NMR, and single crystal X-ray analysis. The coordination mode of the fluorenyl ligand to the titanium metal is η3 manner in each complex. The propylene polymerization is conducted with these complexes at 0 and 25 °C in a semi batch-type method, respectively. The catalytic activity of 1a–1c bearing cumyl-amido ligand is much higher than that of 2a and 2b bearing naphthyl group in amido ligand. High molecular weight polypropylenes are obtained with narrow molecular weight distribution, suggesting a living nature of these catalytic systems at 0 °C. The polymers produced are statistically atactic, regardless of the structure of the complex and the polymerization temperature.
Highlights
Half-sandwich group 4 metal complexeshaving an ansa-monocyclopentadienylamido ligand (CpA) have captured significant attention due to their various copolymerization abilities and stereospecificity as olefin polymerization catalysts [1,2,3,4].The replacement of the Cp ligand by the fluorenyl ligand was effective for the improvement of polymerization activity, copolymerization ability, syndiospecificity, and living polymerization nature to produce novel random and block copolymers with controlled microstructure [5,6,7,8,9,10]
Differential scanning calorimeter (DSC) analyses were performed on TA Q2000 instrument (Waters, New Castle, DE, USA), and the DSC curves of the samples were recorded under a nitrogen atmosphere at a heating rate of 10 ◦ C/min from 40 to 200 ◦ C
The complexes were synthesized in good yield using one-pot reaction of the corresponding ligand
Summary
Half-sandwich group 4 metal complexes (usually named constrained geometry catalysts, CGC). Having an ansa-monocyclopentadienylamido ligand (CpA) have captured significant attention due to their various copolymerization abilities and stereospecificity as olefin polymerization catalysts [1,2,3,4]. The highly syndiospecific polymerization of α-olefin was achieved with Cs -symmetric Ti or Zr complexes by the introduction of alkyl groups on the fluorenyl ligand [11,12,13,14,15]. -symmetric ansa-(fluorenyl)(amido)dimethyltitanium complexes with high activity [19,20,21,22]. S norbornene using Cs-symmetric ansa-(fluorenyl)(amido)dimethyltitanium complexes with high. We synthesized C1-symmetric complex and the other compounds, and found the structure of amido ligand did not affect livingness of catalytic system; the highest mm that the change of the structure of amido ligand did not affect livingness of catalytic system; value wasthe.
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