Corborundanes. II. Derivative chemistry of a very reluctantly reactive bridgehead silicon center

Synthesis and Structure of the First Bridgehead Silylium Ion

“…For example, the usually very labile Si–N bond is resistant to aqueous acidic hydrolysis in Et 2 NSi 4 Me 3 (CH 2 ) 6 , and the reduction of the Si–Cl unit in ClSi 4 Me 3 (CH 2 ) 6 to the hydrosilane HSi 4 Me 3 (CH 2 ) 6 ( 1 ) required prolonged reflux with LiAlH 4 . On the basis of these findings, and in continuation of earlier studies by one of us on the synthesis of mono- and bis-triflates ( 2 and 3 ; Figure ) and complexation studies with super Lewis acids and a theoretical study (DFT and GIAO-NMR) of β-silyl-1-silaadamant-1-yl cations, we report the synthesis and characterization of an arene-solvated bridgehead silylium ion, [Si 4 Me 3 (CH 2 ) 6 ·ArX][CHB 11 Cl 11 ] ([ 4 + ·ArX][CHB 11 Cl 11 ]; ArX = C 7 D 8 , C 6 D 5 Br) derived from the bridgehead silane 1 .…”

“…Despite their high reactivity silylium ions have begun to be employed as catalysts or reagents in synthetic chemistry. − Unlike carbon compounds, nucleophilic substitution at four-coordinate silicon centers takes place essentially exclusively through association mechanisms . This can result in a significant rate reduction for silane substrates in which the silicon center is the apex of a tricyclic species such as the tetrasilaadamantanes XSi 4 Me 3 (CH 2 ) 6 …”

“…10 This can result in a significant rate reduction for silane substrates in which the silicon center is the apex of a tricyclic species such as the tetrasilaadamantanes XSi 4 Me 3 (CH 2 ) 6 . 11 For example, the usually very labile Si−N bond is resistant to aqueous acidic hydrolysis in Et 2 NSi 4 Me 3 (CH 2 ) 6 , and the reduction of the Si−Cl unit in ClSi 4 Me 3 (CH 2 ) 6 to the hydrosilane HSi 4 Me 3 (CH 2 ) 6 (1) required prolonged reflux with LiAlH 4 . 11 On the basis of these findings, and in continuation of earlier studies by one of us on the synthesis of mono-and bis-triflates (2 and 3; Figure 1) and complexation studies with super Lewis acids 12 and a theoretical study (DFT and GIAO-NMR) of β-silyl-1-silaadamant-1-yl cations, 13 The hydride abstraction process, studied computationally via the isodesmic reaction in eq 2, is found to be favorable toward the formation of the silylium ion and becomes more favorable by incorporating solvation effects (PCM).…”

Adamantane-type clusters: compounds with a ubiquitous architecture but a wide variety of compositions and unexpected materials properties

“…[(SiMe)3SiCl(CH2)6] ( 44), [NBu4]Cl, KOH / 2-Methyl-2-butanol, H2O, 80 °C, 30 min Q [44] [(SiMe)3SiOCH2CH2NMe2(CH2)6] ( 48)…”

“…[41][42][43] These clusters described so far are used as the basis for ligand exchange reactions at the Si sites (Method Q, leading to 42-55), oen by exchanging the halides found in various positions. 38,[44][45][46] Asides from derivatization on the silicon atom, the CH 2 moiety can also be a target for lithiation to give stepwise addition of longer C/Si chains (56-60). 47 Lastly, it was also shown that the ligand of a single Si site can be abstracted to obtain a charged cluster cation [(SiMe) 48 Realizing the rst purely Si based adamantanes took a 9 step synthesis, the last one being a rearrangement of a tricyclic compound Si 14 Me 24 to [(SiMe) 4 (SiMe 2 ) 6 ] (62, Fig.…”