The Elusive Silyliumylidene [ClSi:]⁺ and Silathionium [ClSiS]⁺ Cations Stabilized by Bis(Iminophosphorane) Chelate Ligand

Abstract

Donor‐Akzeptor‐Trümpfe: Das Chlorsilyliumyliden‐Salz 2 mit dreifach koordiniertem Silicium(II)‐Atom ist über einen Ligandenaustausch zwischen NHCSiCl2 und dem elektronenreichen Bis(ylid)‐Liganden 1 zugänglich. Das Kation in 2 repräsentiert eine donorstabilisierte Form des [ClSi:]‐Kations und konnte vollständig charakterisiert werden, einschließlich Röntgenstrukturanalyse. Oxidation von 2 mit elementarem Schwefel ergibt 3 als einziges Produkt.

Recent Advances in Silylene Chemistry: Small Molecule Activation En-Route Towards Metal-Free Catalysis

“…The cation in 107 can be thought of as a stable derivative of the parent silyliumylidene SiH + , an extremely reactive species first observed in the 1970s by Douglas and Lutz [94] and later identified in the solar spectrum, and postulated to be an intermediate in space [95]; (For a recent example of a silyliumylidene [ClSi:] + stabilised by a Bis(iminophosphorane) chelate ligand, see: [96]). This makes the isolation of 107 even more remarkable.…”

An isolable, crystalline complex of square-planar silicon(IV)

“…Silicon is the second most abundant element in the Earth's crust, constituting 28 wt % as tetrahedral silicon(IV). 1 During past decades, groundbreaking low-valent states of silicon, such as silylium ions, 2 , 3 silylenes, 4 , 5 , 6 silylium ylidenes, 7 , 8 , 9 , 10 disilenes, 11 disilynes, 12 trisilaallene, 13 or silylones, 14 , 15 have been isolated ( Figure 1 A). 16 The modified electronic structure in those compounds compared with normal-valent silicon(IV) evolved into a linchpin for unique reactivities and catalytic applications.…”

The Pentamethylcyclopentadienylsilicon(II) Cation: Synthesis, Characterization, and Reactivity

“…This is due to the considerable progress made in the chemistry of divalent silicon. Using the concept of kinetic and/or thermodynamic stabilization, several novel classes of compounds have been discovered; the most important ones are presented with their typical structural framework in Scheme 7–29. Their thermodynamic stabilization is realized 1) by electron delocalization from a substituent to the central silicon atom, 2) by the use of chelating or π‐bonded substituents and/or 3) by the complexation with strong σ‐donor ligands L. In the neutral compounds, both di‐coordinate (silylenes) and higher coordinate silicon atoms (silicon(II) species) are present.…”

“…Rather surprisingly, even highly reactive [HalSi : ] + ions can be stabilized in this manner, as documented by the very recent synthesis of salts containing cationic adducts with NHCs of the type [(NHC) 2 →Si : Hal] + (Hal=I,26 Cl;28 S and T in Scheme , respectively). Interestingly, not only NHC molecules, but also a chelating bis(iminophosphorane) ligand can stabilize a [HalSi : ] + cation, as shown by the isolation of a compound containing the [ClSi : ] + species ( U in Scheme ) 29. Rather unexpectedly, NHC molecules can stabilize even the elusive [Si : ] 2+ unit, as documentted by the very recently described dication of the type [(NHC) 3 →Si : ] 2+ ( V in Scheme ) 26.…”