Neutral ansa-bis(fluorenyl)silane neodymium borohydrides: synthesis, structural study and behaviour as catalysts in butadiene–ethylene copolymerisation
作者:Guillaume Cortial、Xavier-Frederic Le Goff、Magali Bousquié、Christophe Boisson、Pascal Le Floch、François Nief、Julien Thuilliez
DOI:10.1039/c0nj00274g
日期:——
The reaction of silylene-bridged bis(fluorenyl)dipotassium salts with neodymium tris(borohydride) afforded new neutral ansa-bis(fluorenyl)silane neodymium borohydrides: (Flu2SiR2)Nd(BH4)(THF) [R2 = Me2, Et2, (CH2)3, Me(Ph), Flu = C13H8] that were better characterised and more soluble than the previously described anionic [(Flu2SiMe2)Nd(BH4)2]â. The X-ray structures of three of these complexes were determined, and their solid-state geometrical parameters are very similar, despite the ring strain introduced by the silacyclobutane bridge in [Flu2Si(CH2)3]Nd(BH4)(THF). The main geometrical features were satisfactorily reproduced by DFT calculations. The catalytic activity of the title complexes in ethyleneâbutadiene copolymerisation reactions was assessed and compared to that of the reported activity of [(Flu2SiMe2)Nd(BH4)2]â under similar conditions. From these results it can be concluded that the cyclo-copolymerisation of ethylene with butadiene is characteristic of a catalyst featuring silylene-bridged bis(fluorenyl) ligands around neodymium, and appears to be independent of the substituents at the silicon atom.
与钕三(硼氢化物)反应的硅烯桥接双(芴基)二钾盐生成了新的中性安萨-双(芴基)硅烷钕硼氢化物:(Flu2SiR2)Nd(BH4)(THF)[R2 = Me2, Et2, (CH2)3, Me(Ph), Flu = C13H8],这些化合物的特征比之前描述的阴离子[(Flu2SiMe2)Nd(BH4)2]⁻更为明显且更易溶解。这三种配合物的X射线结构已被确定,尽管[Flu2Si(CH2)3]Nd(BH4)(THF)中的硅环丁烷桥引入了环张力,但它们的固态几何参数非常相似。主要几何特征通过DFT计算得到了令人满意的再现。该标题配合物在乙烯-丁二烯共聚反应中的催化活性得到了评估,并与在类似条件下报告的[(Flu2SiMe2)Nd(BH4)2]⁻的活性进行了比较。从这些结果可以得出结论,乙烯与丁二烯的环状共聚反应是具有硅烯桥接双(芴基)配体的钕催化剂的特征,且似乎与硅原子的取代基无关。