Institut für Chemie, Carl von Ossietzky Universität Oldenburg, Carl von Ossietzky-Strasse 9-11, D-26129 Oldenburg, Federal Republic of Germany.
J Am Chem Soc. 2013 Jul 17;135(28):10353-61. doi: 10.1021/ja400306h. Epub 2013 Jul 1.
The terphenyl-substituted dibenzosilanorbornadienyl cation 11 was synthesized and isolated in the form of its B(C6F5)4 salt. The salt was characterized by NMR spectroscopy supported by quantum mechanical computations and by an XRD analysis of a corresponding acetonitrilium salt. The thermal fragmentation of 11[B(C6F5)4] in benzene results in the high-yield formation of diphenylterphenylsilylium borate 17[B(C6F5)4]. High-lying intermediates in this process are solvent-complexed terphenylsilyliumylidene 8 and the hydrogen- and phenyl-substituted silylium ion 20. The formation of silylium ion 20 by reaction of silyliumylidene 8 with the solvent benzene demonstrates the high potential of this four valence electron species in C-H bond activation reactions. In addition, the instability of the hydrogen-substituted silylium ion 20 in benzene opens new mechanistic perspectives particular for dihydrogen activation by silyl cationic frustrated Lewis pairs and in general for the dihydrogen activation by strong Lewis acids.
四苯基取代的二苯并硅杂双环[2.2.2]辛二烯阳离子 11 已被合成并以其B(C6F5)4盐的形式分离。该盐通过 NMR 光谱得到了表征，NMR 光谱得到了量子力学计算的支持，并通过相应的乙腈盐的 XRD 分析得到了表征。11[B(C6F5)4]在苯中的热分解导致高产率的二苯基三苯基硅硼酸酯 17[B(C6F5)4]的形成。该过程中较高的中间体是溶剂配位的三苯基硅烯基 8 和氢取代的硅离子 20。通过反应 8 与溶剂苯反应生成硅离子 20，证明了这种四价电子物种在 C-H 键活化反应中具有很高的潜力。此外，氢取代的硅离子 20 在苯中的不稳定性为硅阳离子受阻路易斯对特别是对氢气的活化以及一般情况下对强路易斯酸对氢气的活化开辟了新的机制前景。
