Indolyl-based NCN-pincer titanium group metal complexes:Synthesis and catalytic application for styrene polymerization
Indole worked as the backbone and two side arms at the 1-,and 3-positions were introduced to obtain a 1,3-di-functionalized indolyl compound.After the deprotonation by BuLi,it was reacted with MCl4(M=Ti,Zr,Hf)to form a series of NCN-pincer type titanium group metal complexes(3-Ti,3-Zr,3-Hf).The complexes were character-ized by NMR,elemental analysis,and single-crystal X-ray diffraction.The single-crystal structures revealed that the metal center bonds with the ligand in κ3 NCN modes and three chlorine atoms to form a six-coordinated distorted octa-hedral configuration.Styrene polymerization was investigated with 3-Ti,3-Zr,and 3-Hf using aluminum alkyls and borate reagents as cocatalysts when the concentration ratio of the monomer to the complex was 300∶1.It was found the complexes of different metal centers could efficiently catalyze styrene polymerization with high conversion under room temperature and using AlEt2Cl/(Ph3C)[B(C6F5)4]as cocatalysts,moreover,the hafnium complex displayed the higher activity.The obtained polystyrene was characterized by gel permeation chromatography(GPC)and 13C NMR.The results showed the polymer was atactic and had a low number-average molecular weight(Mn=4 000-8 000).CCDC:2332412,3-Ti;2332412,3-Zr;2332414,3-Hf.
imino substituted indoleNCN-pincer typetitanium group metal complexstyrenepolymerization
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