二环戊二烯基四羰基二铁类化合物催化苯乙烯自由基聚合研究

RADICAL POLYMERIZATION OF STYRENE CATALYZED BY BISCYCLOPENTADIENYL TETRACARBONYL DI-IRON COMPLEXES

以α 溴代异丁酸乙酯为引发剂 ,甲苯作溶剂 ,在温度 80℃下 ,研究了一系列二环戊二烯基四羰基二铁类化合物 [Cp′Fe(CO) 2 ]2 (Cp′ =C5H5,C9H7,C5HMe4 ,Me3SiC5H4 ,C5HPh4 ,t BuC5H4 )催化苯乙烯自由基聚合反应 .结果发现 ,简单环戊二烯基及茚基四羰基二铁类化合物催化苯乙烯自由基聚合都是不可控的 .当茂环上引入大位阻取代基时聚合反应明显变慢 .其中 [C5HMe4 Fe(CO2 ) ]2 在低转化率下分子量Mn 与转化率有很好的线性关系 ,[C5HPh4 Fe(CO) 2 ]2 催化苯乙烯本体聚合Mn 与转化率一直呈线性关系 ,且实际分子量与理论值接近 ,表明取合物的分子量是可控的 .叔丁基取代的化合物 (t BuC5H4 )Fe(CO2 ) ]2 催化苯乙烯聚合的数均分子量与转化率基本成线性关系 ,且分子量分布随转化率增大而变窄 ,表明体系为可控聚合体系 .

A series of biscyclopentadienyl tetracarbonyl di-iron complexes, [Cp'Fe(CO)(2)](2) (Cp' = C5H5, C9H7, C5HMe4, Me3SiC5H4, C5HPh4, t-BuC5H4), were employed for the radical polymerization of styrene in toluene using Me2CBrCO2Et as initiator. It was found that the polymerization was uncontrollable for systems of [C5H5Fe(CO)(2)](2) and [C9H7Fe(CO)(2)](2). When the bulky substituents were introduced to the cyclopentadienyl rings, the polymerization rates became much slower. When [C5HPh4Fe(CO)(2)](2) was used to catalyze the bulk polymerization of styrene, although the molecular weight distribution was somewhat broad, the molecular weight M-n increased linearly with the conversion rate and the measured M-n values were very close to the thoretical values, indicating that the molecular weight is controllable. For the system of [(t-BuC5H4)Fe(CO)(2)](2), the molecular weight M-n increased linearly with the converison rate and the molecular weight distribution decreased with conversion increasing, indicating the polymerization system is controllable.