The Ion‐Like Supersilylium Compound tBu₃Si–F–Al[OC(CF₃)₃]₃

Abstract

The ion-like silylium compounds tBu 3 Si-F-Al[OC (CF 3 ] {1a(X): R = tBu, X = F, Cl; 1b(X): R = Me, X = F, Cl}, could not be generated under these conditions. Generally, at low temperatures (Ͻ -50°C) the halonium salts 1a(Br), 1a(I), 1b(Br), and 1b(I) are stable compounds. However, at higher temperatures 1a(Br), 1a(I), 1b(Br), and 1b(I) undergo R 3 SiX (R = Me, tBu; X = Br, I) elimination to form the highly reactive silyl cations [R 3 Si] + (R = Me, tBu). Two)

Silicon–Halogen Bond Activation in Mixed Si/Al Compounds and an Approach to Intramolecular Stabilized Silylium Ions

“…[34b], , Only those compounds were considered which have three alkyl or aryl groups attached to aluminium and are best suited for a comparison with the structures of 9 . Shorter Al–F distances of 184.1(2), 180.3(1) and 180(1) pm were also found in the closely related Lewis acid base adducts (F 5 C 6 ) 3 Al‐F–SiEt 3 and R 3 Si‐F‐Al[OC(CF 3 ) 3 ] 3 (R = Me,[15a], [15b] R = t Bu). The Si–F‐Al angles are about 160° and result in short F ··· F contacts of 284 ( 9a ) and 292 pm ( 9b ) that are just below the sum of the van der Waals radii (292 to 300 pm) .…”

“…The Si–F bond lengths are in a narrow range of 169.4(1) to 170.2(1) pm and approximately 10 pm longer than in the starting compounds 8 or related compounds with terminal Si–F bonds such as F–SiR 3 (R = alkyl, aryl) . They are in the typical range of Si–F distances with two‐coordinate, bridging F atoms in compounds of the type Li–F–Si or [Si–F–Si] +[47] and are slightly shorter than in typical ion‐like Si compounds including (F 5 C 6 ) 3 Al‐F–SiEt 3 (172.5(2) pm or R 3 Si‐F‐Al[OC(CF 3 ) 3 ] 3 [R = Me (174.4(1),[15a] R = t Bu (175.9(6) pm)]. The Al–F bond lengths show values of 194.3(1) to 197.5(1) pm and are comparable to those in adducts of organoaluminium compounds to F atoms of Aryl‐F groups or BF 3 molecules,[50b], [50i], [50l] a shorter one was detected for the adduct PhF · Al(OR F ) 3 [186.4(2) pm; R = C(CF 3 ) 3 ].…”

Depolymerization of Cellulose and Synthesis of Hexitols from Cellulose Using Heterogeneous Catalysts

“…As shown in Table 1, the sum of the C–Si–C bond angles is greater than those in the supersilylated oxo‐compounds t Bu 3 Si Y ( Y = OH 2 , OH, OM) and smaller than those in the ion‐like supersilylium compounds (e.g. Σ(C–Si–C) in t Bu 3 Si–F–Al(OC(CF 3 ) 3 ) 3 45 = 346.1°). The Si–C bonds of the supersilyl groups in the Brønsted acids [ t Bu 3 SiNH 3 ] + and [ t Bu 3 SiOH 1,5 ] 0.5+ are significantly longer than the related bond lengths of the ion‐like supersilylium compounds, which represent strong Lewis acids (typical Si–C bond length = 1.89 Å for ion‐like supersilylium compounds cf.…”

“…Ref. 45). Interestingly, due to incomplete protonation the structural parameters that were observed for the supersilyl group of [ t Bu 3 SiOH 1,5 ] 0.5+ in t Bu 3 SiOH · (HO 3 SCF 3 ) 0.5 · H 2 O46 lay between those of [ t Bu 3 SiNH 3 ]Cl and t Bu 3 SiOH47 (cf.…”

Unexpected Silaazetidine Formation in the Thermolysis of thf‐Supported Silanimine Et2Si=N–SitBu3·thf

“…Ref. [45]). Interestingly, due to incomplete protonation the structural parameters that were observed for the supersilyl group of [tBu 3 SiOH 1,5 ] 0.5+ in tBu 3 SiOH·(HO 3 SCF 3 ) 0.5 ·H 2 O [46] lay between those of [tBu 3 SiNH 3 ]Cl and tBu 3 SiOH [47] (cf.…”