Martens Arthur, Kreuzer Marvin, Ripp Alexander, Schneider Marius, Himmel Daniel, Scherer Harald, Krossing Ingo
Institut für Anorganische und Analytische Chemie , Freiburger Materialforschungszentrum (FMF) , Universität Freiburg , Albertstr. 21 , 79104 Freiburg , Germany . Email:
Chem Sci. 2019 Jan 10;10(9):2821-2829. doi: 10.1039/c8sc04591g. eCollection 2019 Mar 7.
Instead of yielding the desired silylium ions, the reactions of different alkenes/alkynes with several [MeSi] sources mostly led to oligomerization, or - in the presence of MeSiH - hydrosilylation of the alkenes/alkynes. Yet, from the reaction of 2-butyne with MeSi-F-Al(OR) (R = C(CF)) the salt of the silylated tetramethyl cyclobutenyl cation [MeC-SiMe][--] ([--] = [(RO)Al-F-Al(OR)]) was obtained in good yield (NMR, scXRD, Raman, and IR). All the experimental and calculated evidence suggest a mechanism in which was formed a silylium ion as an intermediate. The removal of the [MeSi] moiety from the cation in was investigated as a means to provide free tetramethyl cyclobutadiene (CBD). However, the addition of [NMe]F, in order to release MeSiF and form CBD, led to the unexpected deprotonation of the cation. The addition of 4-dimethylaminopyridine to remove the [MeSi] cation as a Lewis acid/base adduct, led to an adduct with the four-membered ring in the direct neighborhood of the MeSi group. By the addition of EtO to a solution of , the [F-Al(OR)] anion (and EtO-Al(OR)) was generated from the [--] counterion. Subsequently, the [F-Al(OR)] anion abstracted the [MeSi] moiety from [MeC-SiMe], probably releasing CBD. However, due to the immediate reaction of CBD with [MeC-SiMe] and subsequent oligomerization, it was not possible to use CBD in follow-up chemistry.
不同的烯烃/炔烃与几种[MeSi]源反应，大多导致低聚反应，或者在存在MeSiH的情况下，导致烯烃/炔烃的硅氢化反应，而不是生成预期的硅鎓离子。然而，2-丁炔与MeSi-F-Al(OR)（R = C(CF)）反应，以良好的产率得到了硅烷基化四甲基环丁烯基阳离子[MeC-SiMe][--]（[--] = [(RO)Al-F-Al(OR)]）的盐（通过核磁共振、单晶X射线衍射、拉曼光谱和红外光谱表征）。所有实验和计算证据均表明存在一种以硅鎓离子作为中间体形成的机制。研究了从阳离子中去除[MeSi]部分作为提供游离四甲基环丁二烯（CBD）的一种方法。然而，添加[NMe]F以释放MeSiF并形成CBD，导致阳离子意外地发生去质子化。添加4-二甲基氨基吡啶以去除作为路易斯酸/碱加合物的[MeSi]阳离子，得到了在MeSi基团直接邻位具有四元环的加合物。通过向的溶液中加入EtO，从[--]抗衡离子生成了[F-Al(OR)]阴离子（和EtO-Al(OR)）。随后，[F-Al(OR)]阴离子从[MeC-SiMe]中提取[MeSi]部分，可能释放出CBD。然而，由于CBD与[MeC-SiMe]立即反应并随后发生低聚反应，因此无法在后续化学中使用CBD。
