Stable N‐Heterocyclic Carbene Adducts of Arylchlorosilylenes and Their Germanium Homologues

Filippou, Alexander C.; Chernov, Oleg; Blom, Burgert; Stumpf, Kai W.; Schnakenburg, Gregor

doi:10.1002/chem.200903019

Cited by 146 publications

(91 citation statements)

References 71 publications

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“…The most distinctive spectroscopic features of 2-Br are the low-field shifted The molecular structure of 2-Br reveals a trigonal-pyramidal-coordinated silicon center (sum of bond angles at Si = 290(1)8) that indicates the presence of a stereochemically active lone pair of electrons at the Si atom ( Figure 1). [7] The SiÀC carbene bond lengths of 2-Br (2.007(5) ), [7] SiX 2 A C H T U N G T R E N N U N G (Idipp) (X = Cl 1.985(4) , X = Br 1.989(3) ) [5] and SiCl(C 6 H 3 -2,6-Trip 2 )A C H T U N G T R E N N U N G (Im À Me 4 ) (1.963(2) ) [8] are similar, thereby indicating a strong C carbene !Si donor-acceptor single bond. The mean Si À Br bond length of 2-Br (2.335(6) ) [7] compares well with that of SiBr 2 A C H T U N G T R E N N U N G (Idipp) (2.349(11) ) [5b] but is considerably longer than that of SiBr 2 (r g A C H T U N G T R E N N U N G (SiÀBr) = 2.245(3) ) [9] due to the higher silicon coordination number.…”

Section: A C H T U N G T R E N N U N G (Sidipp) (2-br)mentioning

confidence: 98%

ChromiumSilicon Multiple Bonds: The Chemistry of Terminal N‐Heterocyclic‐Carbene‐Stabilized Halosilylidyne Ligands

Filippou

Chernov

Schnakenburg

2011

Chemistry A European J

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An efficient method for the synthesis of the first N-heterocyclic carbene (NHC)-stabilized halosilylidyne complexes is reported that starts from SiBr(4). In the first step, SiBr(4) was treated with one equivalent of the N-heterocyclic carbene 1,3-bis[2,6-bis(isopropyl)phenyl]imidazolidin-2-ylidene (SIdipp) to give the 4,5-dihydroimidazolium salt [SiBr(3)(SIdipp)]Br (1-Br), which then was reduced with potassium graphite to afford the silicon(II) dibromide-NHC adduct SiBr(2)(SIdipp)(2-Br) in good yields. Heating 2-Br with Li[CpCr(CO)(3)] afforded the complex [Cp(CO)(2)Cr=SiBr(SIdipp)] (3-Br) upon elimination of CO. Complex 3-Br features a trigonal-planar-coordinated silicon center and a very short CrSi double bond. Similarly, the reaction of SiCl(2)(SIdipp) (2-Cl) with Li[CpCr(CO)(3)] gave the analogous chloro derivative [Cp(CO)(2)Cr=SiCl(SIdipp)] (3-Cl). Complex 3-Br undergoes an NHC exchange with 1,3-dihydro-4,5-dimethyl-1,3-bis(isopropyl)-2H-imidazol-2-ylidene (IMe(2)iPr(2)) to give the complex [Cp(CO)(2)CrSiBr(IMe(2)iPr(2))(2)] (4-Br). Compound 4-Br features a distorted-tetrahedral four-coordinate silicon center. Bromide abstraction occurs readily from 4-Br with Li[B(C(6)F(5))(4)] to give the putative silylidene complex salt [Cp(CO)(2)Cr=Si(IMe(2)iPr(2))(2)][B(C(6)F(5))(4)], which irreversibly dimerizes by means of an Si-promoted electrophilic activation of one carbonyl oxygen atom to yield the dinuclear siloxycarbyne complex [Cp(CO)Cr{(μ-CO)Si(IMe(2)iPr(2))(2)}(2-)Cr(CO)Cp][B(C(6)F(5))(4)](2) (5). All compounds were fully characterized, and the molecular structures of 2-Br-5-Br were determined by single-crystal X-ray diffraction. DFT calculations of 3-Br and 3-Cl and their carbene dissociation products [Cp(CO)(2)Cr=Si-X] (X=Cl, Br) were carried out, and the electronic structures of 3-Br, 3-Cl and [Cp(CO)(2)Cr=Si-X] were analyzed by the natural bond orbital method in combination with natural resonance theory.

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Section: A C H T U N G T R E N N U N G (Sidipp) (2-br)mentioning

confidence: 98%

ChromiumSilicon Multiple Bonds: The Chemistry of Terminal N‐Heterocyclic‐Carbene‐Stabilized Halosilylidyne Ligands

Filippou

Chernov

Schnakenburg

2011

Chemistry A European J

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“…Ther eaction of the NHC adduct of arylchlorosilylene [34] 1 with one molar equiv of LiPH 2 . dme (dme = 1,2-dimethoxyethane) at room temperature in THF afforded, after 18 h, the 1,2-dihydrophosphasilene 2,p resumably through tautomerization of its elusive phosphanylsilylene isomer (Scheme 2).…”

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confidence: 99%

A Persistent 1,2‐Dihydrophosphasilene Adduct

et al. 2015

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The reaction of the arylchlorosilylene-NHC adduct ArSi(NHC)Cl [Ar=2,6-Trip2 -C6 H3 ; NHC=(MeC)2 (NMe)2 C] 1 with one molar equiv of LiPH2 (.) dme (dme=1,2-dimethoxyethane) affords the first 1,2-dihydrophosphasilene adduct 2 (ArSi(NHC)(H)PH). The latter is labile in solution and can undergo head-to-tail dimerization to give [ArSi(H)PH]2 3 and "free" NHC. Further stabilization of 2 by complexation with {W(CO)5 } affords the isolable 1,2-dihydrophosphasilene-tungsten complex 4 [ArSi(NHC)(H)P(H)W(CO)5 ]. Additionally, the new 1-silyl-2-hydrophosphasilene ArSi(NHC)(H)PSiMe3 5 could be synthesized and structurally characterized. DFT studies confirmed that the SiP bond in 2 and 4 is mostly zwitterionic with drastically decreased double-bond character.

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“…Young PTFE tubes. mTerSiHCl 2 , chlorosilylene C and ImMe 4 were synthesized according to procedures described in literature [54,73,74]. NMR spectra were recorded on Bruker AV-400 spectrometer (Rheinstetten, Germany) at ambient temperature (300 K).…”

Section: General Methods and Instrumentsmentioning

confidence: 99%

“…A theoretical assessment of the observed divergent reactivity was provided by Szilvási and coworkers, revealing a unique insertion step to form the 1,4 adducts, followed by varying pathways towards the products [53]. The NHC-stabilized arylchlorosilylene corresponding to A has already been published by Filippou and coworkers in 2010, as well as the chlorosilylene with sterically more demanding mTer iPr ligand (mTer iPr = 2,6-Tipp 2 C 6 H 3 ) [54]. Subsequently, the mTer iPr -chlorosilylene was employed as the precursor for the preparation of a silylidyne complex Cp(CO) 2 Mo≡Si(mTer iPr ) [55].…”

Section: Introductionmentioning

confidence: 96%

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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Stable N‐Heterocyclic Carbene Adducts of Arylchlorosilylenes and Their Germanium Homologues

Cited by 146 publications

References 71 publications

ChromiumSilicon Multiple Bonds: The Chemistry of Terminal N‐Heterocyclic‐Carbene‐Stabilized Halosilylidyne Ligands

ChromiumSilicon Multiple Bonds: The Chemistry of Terminal N‐Heterocyclic‐Carbene‐Stabilized Halosilylidyne Ligands

A Persistent 1,2‐Dihydrophosphasilene Adduct

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

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