Nucleophilically assisted and cationic ring-opening polymerization of tin-bridged [1]ferrocenophanes.
Nucleophilically assisted and cationic ring-opening polymerization of tin-bridged [1]ferrocenophanes.
复制标题
锡桥[1]二茂铁的亲核辅助和阳离子开环聚合。
DOI：
10.1021/ja020206v
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发表时间：
2002
影响因子：
15
通讯作者：
I. Manners
中科院分区：
文献类型：
--
作者：
T. Baumgartner;F. Jäkle;R. Rulkens;G. Zech;A. Lough;I. Manners
为了获得机理上的见解，详细研究了溶液中锡桥[1]二茂铁番Fe（eta-C（5）H（4））（2）SnR（2）3a（R = t-Bu）和3b（R = Mes）的有趣的“自发”室温开环聚合（ROP）。这些研究探索了非亲核添加剂如自由基和自由基陷阱、中性和阴离子亲核试剂、刘易斯酸、质子物种和其他阳离子亲电试剂的影响。值得注意的是，基于这项研究，提出了两种新的方法和机制的应变[1]二茂铁番的ROP。首先，由于发现胺亲核试剂如吡啶的加入强烈地加速了溶液中的聚合速率，因此提出了一种新的亲核试剂辅助的ROP方法。这在环境温度下在溶液中甚至在氯硅烷的存在下操作，但与二茂铁烷的阴离子聚合不同，不涉及氯代阴离子。其次，发现添加少量亲电物质H（+）和Bu（3）Sn（+）导致阳离子ROP过程。这些研究表明，锡桥[1]二茂铁烷的“自发”ROP可能是虚假的、痕量的刘易斯碱性或酸性杂质的存在的结果。所报道的新的ROP机制可能对其他烯酚烷的ROP具有普遍意义（例如，用于熔体中的热ROP）和用于含有第14族元素的其它金属杂环。
To obtain mechanistic insight, detailed studies of the intriguing "spontaneous" ambient temperature ring-opening polymerization (ROP) of tin-bridged [1]ferrocenophanes Fe(eta-C(5)H(4))(2)SnR(2) 3a (R = t-Bu) and 3b (R = Mes) in solution have been performed. The investigations explored the influence of non-nucleophilic additives such as radicals and radical traps, neutral and anionic nucleophiles, Lewis acids, protic species, and other cationic electrophiles. Significantly, two novel methodologies and mechanisms for the ROP of strained [1]ferrocenophanes are proposed based on this study. First, as the addition of amine nucleophiles such as pyridine was found to strongly accelerate the polymerization rate in solution, a new nucleophilicallyassisted ROP methodology was proposed. This operates at ambient temperature in solution even in the presence of chlorosilanes but, unlike the anionic polymerization of ferrocenophanes, does not involve cyclopentadienyl anions. Second, the addition of small quantities of the electrophilic species H(+) and Bu(3)Sn(+) was found to lead to a cationic ROP process. These studies suggest that the "spontaneous" ROP of tin-bridged [1]ferrocenophanes may be a consequence of the presence of spurious, trace quantities of Lewis basic or acidic impurities. The new ROP mechanisms reported are likely to be of general significance for the ROP of other metallocenophanes (e.g., for thermal ROP in the melt) and for other metallacycles containing group 14 elements.