“Tamed” Silylium Ions: Versatile in Catalysis

Abstract

Cations for all seasons: Silylium cations, because of their high Lewis acidity, are suitable for catalysis like almost no other class of reactive cations. Starting from a new, elegant synthetic route to triarylsilylium ions and their application in hydrogen activation, the general potential of silylium ions in synthesis is discussed.

B(C6F5)3 catalysis accelerates the hydrosilane chlorination by Ph3CCl

“…Based on the above results we propose, that the mechanism of hydrosilane chlorination (Scheme ) is very similar to the one published previously for hydrosilane hydroxylation . A reaction of B(C 6 F 5 ) 3 with Ph 3 CCl generates the key catalytic species [Ph 3 C] + [ClB(C 6 F 5 ) 3 ] − , which in turn reacts with the hydrosilane to form a corresponding silylium species [R 3 Si] + [ClB(C 6 F 5 ) 3 ] − as was previously demonstrated for an analogous reaction of hydrosilanes with [Ph 3 C] + [B(C 6 F 5 ) 4 ] − . However, the species [R 3 Si] + [ClB(C 6 F 5 ) 3 ] − is proposed to be unstable as it consists of a strongly electrophilic silylium cation in combination with nucleophilic chlorine atom.…”

“…Similarly, the 11 B NMR spectrum showed a disappearance Based on the above results we propose, that the mechanism of hydrosilane chlorination (Scheme 3) is very similar to the one published previously for hydrosilane hydroxylation. [15] A reaction of B(C 6 F 5 ) 3 [20,21] However, the species [R 3 Si] + [ClB(C 6 F 5 ) 3 ] − is proposed to be unstable as it consists of a strongly electrophilic silylium cation in combination with nucleophilic chlorine atom. Therefore we propose its immediate decomposition into the corresponding chlorosilane and recuperation of B(C 6 F 5 ) 3 .…”

Benzhydrylium and tritylium ions: complementary probes for examining ambident nucleophiles

“…These carbocation-induced oxidations have been used, for example, for the preparation of metalcomplexed cationic π-systems [41][42][43][44][45][46][47], silylium ions [48,49], polycyclic aromatic compounds [50], and the Fig. 5: Oxidations of silyl enol ethers and enamines through hydride abstraction by tritylium ions [15,16].…”

Reversible Alkene Binding and Allylic C–H Activation with an Aluminum(I) Complex

“…Since the turn of the 21 st century, there has been a growing realisation that main group compounds can imitate the behaviour of transition metal complexes. [1][2][3][4] The identication of reversible redox processes involving substrate activation is now widely believed to be the most important bottleneck for developing transition-metal-like catalytic cycles. While examples of the oxidative addition of substrates to low-valent main group complexes are rife in the literature, reversible behaviour involving reductive elimination is far less common.…”