A novel ligand (3), in which the indenyl group is linked to a β-diketone moiety through a three-carbon bridge, andits titanium complex (4) were synthesized. The titanium complex was employed as a metallocene analog w...A novel ligand (3), in which the indenyl group is linked to a β-diketone moiety through a three-carbon bridge, andits titanium complex (4) were synthesized. The titanium complex was employed as a metallocene analog with co-catalystmethylaluminoxane (MAO) in catalytic syndiospecific polymerization of styrene to give highly syndiotactic polystyrene(s-PS, 96%-97%). Polymerization temperature (T_p) strongly influenced the catalytic activity and syndiotacticity of theproduced PS. The activities of catalyst 4 increase from 1.84×10~6 to 3.26×10~6 gPS/molTi·h with the increase of T_p from60℃ to 80℃ and the syndiotacticities of the produced s-PS also increase slightly. Then, both the catalytic activity and thesyndiotacticity of PS decrease at T_p of 90℃.展开更多
Main observation and conclusion Styrene polymerization catalyzed by the half-titanocenes CpTiCl_(2)[1,3-R_(2)(CH_(2)N)_(2)C=N](6b:R=_(2),6-Me_(2)C_(6)H_(3),T_(4):R=_(2),4,6-Me_(3)C_(6)H_(2);T5:R=_(2),6-iPr_(2)C_(6)H_(...Main observation and conclusion Styrene polymerization catalyzed by the half-titanocenes CpTiCl_(2)[1,3-R_(2)(CH_(2)N)_(2)C=N](6b:R=_(2),6-Me_(2)C_(6)H_(3),T_(4):R=_(2),4,6-Me_(3)C_(6)H_(2);T5:R=_(2),6-iPr_(2)C_(6)H_(3))was carried out in the presence of methylaluminoxane(MAO).Compared to the styrene conversion(31%)and syndiospecific index(45%)using reported 6b as precatalyst,T5 bearing ligand with isopropyl substitutes on the N-aryl-rings exhibits much higher styrene conversion(61%)and syndiospecific index(99%),indicating that the catalytic behavior could be improved obviously by the introduction of electronic donating and steric bulky substituents.One N atom in imidazolin-_(2)-iminato ligand was replaced by O atom,affording half-titanocenes CpTiCl_(_(2))[3-C6H5(CH_(2)N)(CH_(2)O)C=N(T1)and CpTiCl_(_(2))[_(2),6-Me_(2)(C6H3O)(NiPr_(2))C=N](T_(2)).Compared to 6b,both higher styrene conversion and syndiospecific index are afforded by using half-titanocene T1 containing_(2)-imino-3-phenyloxazolidine ligand.All the results illustrate that both the chemical structure and the nature of substituents of the ligand have obvious influence on the styrene conversion and syndiospecific index in the polymerization of styrene.All the resulting syndiotactic polystyrenes(sPSs)are highly syndiospecific(rrr>99%).Correspondingly,the sPS prepared using T5/MAO catalytic system exhibits high melting point and narrow molecular weight distribution.The results might show new light on designing more efficient half-titanocenes for styrene polymerization with both high styrene conversion and high syndiospecific selectivity.展开更多
[t-BuNSiMe_2(2,7-t-Bu_2Flu)]ZrMe_2 and[t-BuNSiMe_2(3,6-t-Bu_2Flu)]ZrMe_2 were synthesized,and the solid structure of complex[t-BuNSiMe_2(2,7-t-Bu_2Flu)]ZrMe_2 was elucidated by single crystal X-ray analysis.These comp...[t-BuNSiMe_2(2,7-t-Bu_2Flu)]ZrMe_2 and[t-BuNSiMe_2(3,6-t-Bu_2Flu)]ZrMe_2 were synthesized,and the solid structure of complex[t-BuNSiMe_2(2,7-t-Bu_2Flu)]ZrMe_2 was elucidated by single crystal X-ray analysis.These complexes were applied for propylene polymerization using dried modified methylaluminoxane as a cocatalyst at 0℃and 20℃in toluene.Both systems did not show activity at 0℃,but they conducted the polymerization at 20℃.The introduction of t-butyl substituents to the fluorenyl ligand improved the activ...展开更多
基金This project was supported by the National Natural Science Foundation of China (No. 29734141).
文摘A novel ligand (3), in which the indenyl group is linked to a β-diketone moiety through a three-carbon bridge, andits titanium complex (4) were synthesized. The titanium complex was employed as a metallocene analog with co-catalystmethylaluminoxane (MAO) in catalytic syndiospecific polymerization of styrene to give highly syndiotactic polystyrene(s-PS, 96%-97%). Polymerization temperature (T_p) strongly influenced the catalytic activity and syndiotacticity of theproduced PS. The activities of catalyst 4 increase from 1.84×10~6 to 3.26×10~6 gPS/molTi·h with the increase of T_p from60℃ to 80℃ and the syndiotacticities of the produced s-PS also increase slightly. Then, both the catalytic activity and thesyndiotacticity of PS decrease at T_p of 90℃.
基金support from the National Natural Science Foundation of China(21634002)the Fundamental Research Funds for the Central Universities(XK1802-2,XK1802-1)。
文摘Main observation and conclusion Styrene polymerization catalyzed by the half-titanocenes CpTiCl_(2)[1,3-R_(2)(CH_(2)N)_(2)C=N](6b:R=_(2),6-Me_(2)C_(6)H_(3),T_(4):R=_(2),4,6-Me_(3)C_(6)H_(2);T5:R=_(2),6-iPr_(2)C_(6)H_(3))was carried out in the presence of methylaluminoxane(MAO).Compared to the styrene conversion(31%)and syndiospecific index(45%)using reported 6b as precatalyst,T5 bearing ligand with isopropyl substitutes on the N-aryl-rings exhibits much higher styrene conversion(61%)and syndiospecific index(99%),indicating that the catalytic behavior could be improved obviously by the introduction of electronic donating and steric bulky substituents.One N atom in imidazolin-_(2)-iminato ligand was replaced by O atom,affording half-titanocenes CpTiCl_(_(2))[3-C6H5(CH_(2)N)(CH_(2)O)C=N(T1)and CpTiCl_(_(2))[_(2),6-Me_(2)(C6H3O)(NiPr_(2))C=N](T_(2)).Compared to 6b,both higher styrene conversion and syndiospecific index are afforded by using half-titanocene T1 containing_(2)-imino-3-phenyloxazolidine ligand.All the results illustrate that both the chemical structure and the nature of substituents of the ligand have obvious influence on the styrene conversion and syndiospecific index in the polymerization of styrene.All the resulting syndiotactic polystyrenes(sPSs)are highly syndiospecific(rrr>99%).Correspondingly,the sPS prepared using T5/MAO catalytic system exhibits high melting point and narrow molecular weight distribution.The results might show new light on designing more efficient half-titanocenes for styrene polymerization with both high styrene conversion and high syndiospecific selectivity.
文摘[t-BuNSiMe_2(2,7-t-Bu_2Flu)]ZrMe_2 and[t-BuNSiMe_2(3,6-t-Bu_2Flu)]ZrMe_2 were synthesized,and the solid structure of complex[t-BuNSiMe_2(2,7-t-Bu_2Flu)]ZrMe_2 was elucidated by single crystal X-ray analysis.These complexes were applied for propylene polymerization using dried modified methylaluminoxane as a cocatalyst at 0℃and 20℃in toluene.Both systems did not show activity at 0℃,but they conducted the polymerization at 20℃.The introduction of t-butyl substituents to the fluorenyl ligand improved the activ...
