A Cyclic Silylone (“Siladicarbene”) with an Electron‐Rich Silicon(0) Atom

Xiong, Yun; Yao, Shenglai; Inoue, Shigeyoshi; Epping, Jan Dirk; Drieß, Matthias

doi:10.1002/anie.201302537

Cited by 253 publications

(202 citation statements)

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“…5 Approximately two decades after the first report 1 of silylene (R 2 Si:), the syntheses of silylones (cAAC) 2 Si with two-coordinate silicon were reported (cAAC = cyclic alkyl(amino) carbene, Scheme 1g). 6 Later on, a cyclic silylone (bNHC)Si (Scheme 1h) was prepared by Driess et al 7 Silylone features a silicon atom in the oxidation state zero which is stabilized by two carbene ligands. Consequently, this silicon atom contains two pairs of electrons.…”

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confidence: 99%

Electron-Induced Conversion of Silylones to Six-Membered Cyclic Silylenes

et al. 2014

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A silicon atom in the zero oxidation state stabilized by two carbene ligands is known as siladicarbene (silylone). There are two pairs of electrons on the silicon atom in silylone. This was recently confirmed by both experimental and theoretical charge density investigations. The silylone is stable up to 195°C in an inert atmosphere. However, a substoichiometric amount (33 mol%) of potassium metal triggers the activation of the unsaturated C:Si:C backbone, leading to a selective reaction with a tertiary C−H bond in an atom-economical approach to form a six-membered cyclic silylene with three-coordinate silicon atom. Cyclic voltammetry shows that this reaction proceeds via the formation of a silylone radical anion intermediate, which is further confirmed by EPR spectroscopy.

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confidence: 99%

Electron-Induced Conversion of Silylones to Six-Membered Cyclic Silylenes

et al. 2014

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“…Key to these developments have been the usage of suitable synthetic methodologies in combination with thermodynamic and kinetic stabilization by appropriately chosen ligands. In particular, for the heavier carbon analogue silicon, a plethora of studies reported new low-valent compounds in recent years [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] and the chemistry of silylene base adducts has already been carefully developed [14,[26][27][28][29][30][31][32][33][34][35][36]. Before these findings, silyliumylidene ions, cationic Si(II) species were found to be promising as similar versatile Lewis amphiphiles [37,38].…”

Section: Introductionmentioning

confidence: 99%

“…As NHCs are strong σ donors, donors, their application in main group chemistry enabled the isolation of a large variety of low coordinate and low-valent main group compounds [41,42]. The first NHC-stabilized silyliumylidenes, III and IV were synthesized by Filippou and coworkers via a three-step protocol from SiI4 [28], and by Driess and coworkers through the reaction of Roesky's NHC-stabilized dichlorosilylene with their bridged bis-carbene ligand [23].…”

Section: Introductionmentioning

confidence: 99%

“…Although a handful of silyliumylidenes have been reported in the last few years, reactivity studies are limited to the activation of elemental sulfur [24,48], the synthesis of a stable silylone from IV [23], and the catalytic application of I in the degradation of ethers [49]. For comparison, the neutral silylene derivative of silyliumylidene II (Figure 1) has been applied in the activation of several small molecules such as NH 3 , H 2 S, H 2 O, AsH 3 and PH 3 [50][51][52].…”

Section: Introductionmentioning

confidence: 99%

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S–H Bond Activation in Hydrogen Sulfide by NHC-Stabilized Silyliumylidene Ions

et al. 2018

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Reactivity studies of silyliumylidenes remain scarce with only a handful of publications to date. Herein we report the activation of S-H bonds in hydrogen sulfide by mTer-silyliumylidene ion A (mTer = 2,6-Mes 2 -C 6 H 3 , Mes = 2,4,6-Me 3 -C 6 H 2 ) to yield an NHC-stabilized thiosilaaldehyde B. The results of NBO and QTAIM analyses suggest a zwitterionic formulation of the product B as the most appropriate. Detailed mechanistic investigations are performed at the M06-L/6-311+G(d,p)(SMD: acetonitrile/benzene)//M06-L/6-311+G(d,p) level of density functional theory. Several pathways for the formation of thiosilaaldehyde B are examined. The energetically preferred route commences with a stepwise addition of H 2 S to the nucleophilic silicon center. Subsequent NHC dissociation and proton abstraction yields the thiosilaaldehyde in a strongly exergonic reaction. Intermediacy of a chlorosilylene or a thiosilylene is kinetically precluded. With an overall activation barrier of 15 kcal/mol, the resulting mechanistic picture is fully in line with the experimental observation of an instantaneous reaction at sub-zero temperatures.

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“…The generation of such a cation is easier in the gas phase, which provides an environment devoid of possible interfering solvents. However, their generation in the condensed phase is very difficult due to highly electrophilic 55 nature of R 3 E + and their propensity to react with any donor moiety, even with arenes. Therefore, bulky donor substituents are required to quench the electrophilicity of the cation as well as to shield the cationic center from any nucleophilic attack.…”

Section: Introductionmentioning

confidence: 99%

Cations and dications of heavier group 14 elements in low oxidation states

et al. 2015

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Cations and dications of heavier group 14 elements in their low oxidation state have received widespread attention in recent years. The journey started with the isolation of a series of cations of the composition [(C5Me5)E:](+) [E = Si-Pb], followed by the more recent isolation of a Ge(ii) dication encapsulated within a cryptand, a carbodiphosphorane stabilized [GeCl](+) monocation with a two coordinate Ge atom, Si(ii) cations and dications stabilized by N-heterocyclic carbenes (NHCs), which highlights the ongoing growth and interest in the chemistry of tetrel(ii) cations. This is presumably because the central atom (E) in these compounds contains two or three unoccupied valence orbitals as well as holds a lone pair of electrons. Such an electronic description represents ambiphilicity, which is of great interest for catalysis. The successful synthesis of divalent group 14 cations requires new synthetic strategies based on the sterically demanding neutral or monoanionic ligands, utilization of counter anions, and solvents with low nucleophilicity in order to minimize the degree of interactions with the cations. An alternative approach for the realization of divalent cations of group 14 elements is their coordination to the transition metals. This synthetic approach was successfully applied for the isolation of a range of transition metal coordinated divalent cations of group 14 elements. Apart from arousing academic interest some of these cations have found application as activators in the Ziegler-Natta polymerization of alkenes.

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A Cyclic Silylone (“Siladicarbene”) with an Electron‐Rich Silicon(0) Atom

Cited by 253 publications

References 47 publications

Electron-Induced Conversion of Silylones to Six-Membered Cyclic Silylenes

Electron-Induced Conversion of Silylones to Six-Membered Cyclic Silylenes

S–H Bond Activation in Hydrogen Sulfide by NHC-Stabilized Silyliumylidene Ions

Cations and dications of heavier group 14 elements in low oxidation states

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