Reactivity of the Bicyclic Amido-Substituted Silicon(I) Ring Compound Si4{N(SiMe3)Mes}4 with FLP-Type Character |
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| Authors: | Dr Kevin Schwedtmann Michael Quest Dr Benedikt J Guddorf Jan Keuter Dr Alexander Hepp Dr Milica Feldt Jörn Droste Prof?Dr Michael Ryan Hansen Dr Felicitas Lips |
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| Institution: | 1. Westfälische Wilhelms-Universität Münster Institut für Anorganische und Analytische Chemie, Corrensstraße 28–30, 48149 Münster, Germany;2. Westfälische Wilhelms-Universität Münster Organisch Chemisches Institut and Center for Multiscale Theory and Computation, Corrensstraße 36, 48149 Münster, Germany;3. Westfälische Wilhelms-Universität Münster Institut für Physikalische Chemie, Corrensstraße 28–30, 48149 Münster, Germany |
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| Abstract: | The bicyclic amido-substituted silicon(I) ring compound Si4{N(SiMe3)Mes}4 2 (Mes=Mesityl=2,4,6-Me3C6H2) features enhanced zwitterionic character and different reactivity from the analogous compound Si4{N(SiMe3)Dipp}4 1 (Dipp=2,6-iPr2C6H3) due to the smaller mesityl substituents. In a reaction with the N-heterocyclic carbene NHC (1,3,4,5-tetramethyl-imidazol-2-ylidene), we observe adduct formation to give Si4{N(SiMe3)Mes}4 ? NHC ( 3 ). This adduct reacts further with the Lewis acid BH3 to yield the Lewis acid–base complex Si4{N(SiMe3)Mes}4 ? NHC ? BH3 ( 4 ). Coordination of AlBr3 to 2 leads to the adduct 5 . Calculated proton affinities and fluoride ion affinities reveal highly Lewis basic and very weak Lewis acidic character of the low-valent silicon atoms in 1 and 2 . This is confirmed by protonation of 1 and 2 with Brookharts acid yielding 6 and 7 . Reaction with diphenylacetylene only occurs at 111 °C with 2 in toluene and is accompanied by fragmentation of 2 to afford the silacyclopropene 8 and the trisilanorbornadiene species 9 . |
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| Keywords: | amines frustrated Lewis pairs inorganic ring systems N-heterocyclic carbenes silicon |
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