A Free Silanide from Nucleophilic Substitution at Silicon(II)

Witteman, Léon; Evers, Tim; Lutz, Martin; Moret, Marc‐Etienne

doi:10.1002/chem.201801435

Cited by 8 publications

(24 citation statements)

References 72 publications

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“…The experimental methods and parameters of the X-ray crystal structure determinations are detailed in the Supporting Information. The compounds (tmim)H 3 , 32 (tmim)Na 3 , 23 (tmim)K 3 , 23 and (tmim)Si – 23 were prepared according to reported procedures.…”

Section: Experimental Sectionmentioning

confidence: 99%

Synthesis and Complexation of a Free Germanide Bearing a Tridentate N-Heterocyclic Substituent

et al. 2019

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The tris-N-heterocycle germanide (tmim)Ge– (1) (tmimH3 = tris(3-methylindol-2-yl)methane) was synthesized by nucleophilic substitution for the tmim3– trianion on GeCl2·dioxane. In combination with the previously reported (tmim)Si– and (tmim)P analogues, it provides a convenient model for investigating the influence of the central atom on the properties of isoelectronic ligands. Complexation of the germanide (tmim)Ge– to CuCl resulted in the dimeric chloro cuprate [(tmim)GeCu(μ-Cl)]22–, which is prone to dissociation in MeCN to form the neutral, solvated germylcopper (tmim)GeCu(NCMe)3. The reaction of 1 with Fe2(CO)9 afforded the germyl iron tetracarbonyl [(tmim)GeFe(CO)4]−. Analysis of the ν̃(CO) infrared absorption bands in this complex indicates that the combined electron donating and accepting properties of 1 are found in between those of (tmim)P and (tmim)Si–. In contrast to (tmim)Si–, (tmim)Ge– is reluctant to coordinate to FeCl2, likely because of its softer Lewis base character. Key structural features of the ligands and complexes reflect changes in their electronic properties. In particular, the N–Ge–N angles increase upon coordination to a metal fragment, suggesting increasing hybridization of the Ge s- and p-orbitals. These findings will be useful in further understanding low-valent heavier group 14 complexes in organometallic chemistry.

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Section: Experimental Sectionmentioning

confidence: 99%

Synthesis and Complexation of a Free Germanide Bearing a Tridentate N-Heterocyclic Substituent

et al. 2019

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“…Constraining N ‐skatyl moieties into the cage structure B (p K a MP2 =234.5) decreases the sum of N^Si^N angles (Σ N^Si^N ) from 324.7° in A to 311.6° B , while reducing the p K a MP2 by an additional 7.1 units, which is about one fourth of the electron withdrawal contribution. This trend is continued by the more constrained C‐tethered analogue C , which has not been observed experimentally, but its conjugate base has been isolated [17, 44] . With a Σ N^Si^N of 300.5°, its gas‐phase p K a MP2 equals 229.6.…”

Section: Resultsmentioning

confidence: 91%

“…Zwitterionic Si II silanide TSMPSi ( 1 ) was isolated from the reaction of the tris‐indolide salt TSMPK 2 ( 3 ) [16] with Idipp→SiCl 2 used as a Si II source (Scheme 1). [17] The corresponding cationic Si IV silane, [TSMPSiH] + BAr F 4 − ( 2 BARF ), was synthesized by protonation with an equimolar amount of Brookhart's acid (HBAr F 4 ⋅2 Et 2 O). Attempted protonation with HCl led to an intractable mixture of insoluble products, highlighting the importance of a non‐coordinating anion in this reaction (Section S5.1.1).…”

Section: Resultsmentioning

confidence: 99%

Strain‐Modulated Reactivity: An Acidic Silane

et al. 2021

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Compounds of main‐group elements such as silicon are attractive candidates for green and inexpensive catalysts. For them to compete with state‐of‐the‐art transition‐metal complexes, new reactivity modes must be unlocked and controlled, which can be achieved through strain. Using a tris(2‐skatyl)methylphosphonium ([TSMPH3]+) scaffold, we prepared the strained cationic silane [TSMPSiH]+. In stark contrast with the generally hydridic Si−H bond character, it is acidic with an experimental pKaDMSO within 4.7–8.1, lower than in phenol, benzoic acid, and the few hydrosilanes with reported pKa values. We show that ring strain significantly contributes to this unusual acidity along with inductive and electrostatic effects. The conjugate base, TSMPSi, activates a THF molecule in the presence of CH‐acids to generate a highly fluxional alkoxysilane via trace amounts of [TSMPSiH]+ functioning as a strain‐release Lewis acid. This reaction involves a formal oxidation‐state change from SiII to SiIV, presenting intriguing similarities with transition‐metal‐mediated processes.

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“…73 Additionally, we recently showed that the tmim 3– trianion can fully substitute the Si(II) center in (Idipp)SiCl 2 (Idipp = 2,3-dihydro-1,3-bis(2,6-diisopropylphenyl)-1H-imidazol-2-ylidene) to form the naked silanide (tmim)Si – . 33 Scaffold tmimH 3 was synthesized according to the literature procedure, 101 followed by deprotonation using NaH. The reaction of 8 with NEt 4 - 2 was initially conducted in THF at 60 °C.…”

Section: Multidentate N-donorsmentioning

confidence: 99%

“… 32 In this context, silyl ligands bearing electron-withdrawing N-heterocyclic substituents such as N-pyrrolyl or N-indolyl represent an attractive yet underexplored ligand class, with only a handful of representatives known to date. 33 …”

Section: Introductionmentioning

confidence: 99%

Synthesis of N-Heterocycle Substituted Silyl Ligands within the Coordination Sphere of Iron

2018

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N-Heterocycle-substituted silyl iron complexes have been synthesized by nucleophilic substitution at trichlorosilyl ligands bound to iron. The homoleptic (tripyrrolyl)- and tris(3-methylindolyl)silyl groups were accessed from (Cl3Si)CpFe(CO)2 (Cl3SiFp) by substitution of chloride with pyrrolide or 3-methylindolide, respectively. Analogously, nucleophilic substitution of Cl with pyrrolide on the anionic Fe(0) synthon Cl3SiFe(CO)4– generates the (tripyrrolyl)silyl ligand, bound to the iron tetracarbonyl fragment. The bulkier 2-mesitylpyrrolide substitutes a maximum of 2 chlorides on Cl3SiFp under the same conditions. The tridentate, trianionic nucleophile tmim (tmimH3 = tris(3-methylindol-2-yl)methane) proves reluctant to perform the substitution in a straightforward manner; instead, ring-opening and incorporation of THF occurs to form the tris-THF adduct tmim(C4H8O)3SiFe(CO)4–. The bidentate, monoanionic nucleophile 2-(dipp-iminomethyl)pyrrolide (DippIMP, dipp = 2,6-diisopropylphenyl) shows chloride displacement and addition of a second DippIMP moiety on the imine backbone. The heterocycle-based silyl ligands were shown to be sterically and electronically tunable, moderately electron-donating ligands. The presented approach to new silyl ligands avoids strongly reducing conditions and potentially reactive hydrosilane intermediates.

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A Free Silanide from Nucleophilic Substitution at Silicon(II)

Cited by 8 publications

References 72 publications

Synthesis and Complexation of a Free Germanide Bearing a Tridentate N-Heterocyclic Substituent

Synthesis and Complexation of a Free Germanide Bearing a Tridentate N-Heterocyclic Substituent

Strain‐Modulated Reactivity: An Acidic Silane

Synthesis of N-Heterocycle Substituted Silyl Ligands within the Coordination Sphere of Iron

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