Alkali Metal Carbenoids: A Case of Higher Stability of the Heavier Congeners

Molitor, Sebastian; Gessner, Viktoria H.

doi:10.1002/ange.201601356

Cited by 17 publications

(4 citation statements)

References 84 publications

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“…The same compound can be obtained via the "deprotonation−oxidation with C 2 Cl 6 −deprotonation" sequence mentioned above, giving the possibility to obtain carbenoid compounds for which the corresponding geminal dianion are not stable. 47 The formation of related carbenoids from several stable dianions of bis-iminophosphoranes was attempted. With the bulky alkyl adamantyl group, the carbenoid is not stable.…”

Section: Reactivity Of Geminal-dilithio Derivativesmentioning

confidence: 99%

Geminal Dianions Stabilized by Main Group Elements

2019

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This review is dedicated to the chemistry of stable and isolable species that bear two lone pairs at the same C center, i.e. geminal dianions, stabilized by main group elements. Three cases can thus be considered: the gem dilithio derivative, for which the two substituents at C are neutral, the ylidiide derivatives, for which one substituent is neutral while the other is charged, and finally the geminal bisylides, for which the two substituents are positively charged. In this review the syntheses and electronic structures of the geminal dianions are presented, followed by the studies dedicated to their reactivity toward organic substrates and finally to their coordination chemistry and applications. Reactivity of doubleylides towards organic compounds. 4.4. Coordination chemistry of double ylides to metallic species. 4.4.1. Coordination to Group 2 Metals. 4.4.2. Coordination to Actinides: Uranium Complexes 4.4.3. Coordination to Group 4 Metals: Zirconium Complexes 4.4.4. Coordination to Group 6 Metals: Tungsten Complexes 4.4.5. Coordination to Group 7 Metals: Manganese and Rhenium Complexes 4.4.6. Coordination to Group 8 Metals: Iron Complexes 4.4.7. Coordination to Group 9 Metals: Rhodium and Iridium Complexes 4.4.8. Coordination to Group 10 Metals 4.4.9. Coordination to Group 11 (Coinage) Metals 4.4.10. Coordination to Group 12 Metals 4.5. Reactivity of double ylides towards main group elements. 4.5.1. Group 13 4.5.2. Group 14 4.5.3. Group 15 4.5.4. Group 16 4.5.5. Group 17 4.6. Carbodicarbenes 4.6.1. Synthesis 4.6.2. Reactivity 4.6.3. Coordination chemistry 4.6.4. Reactivity with main group elements 5. Conclusion 6. Acknowledgements 7. References lengths in complexes [(7)Mg(THF)] 2 and [(14)Mg(THF) 3 ] at 2.156(5)Å and 2.113(4)Å resp. are as expectedly significantly shorter than the ones measured in the dimers [(6a)Mg] 2 and [(10)Mg] 2 at 2.225(2)Å (av.) and 2.267(3)Å (av.). Electronic structureThe question of the nature of the bond between the AE metal and C was addressed. Harder et al.performed a DFT study first on models of [(6a)Ca] 2 and [(6f)Ca] where H atoms were considered in place of the real phenyl groups at P and groups (SiMe 3 and Ar resp.) at N. 49 In the case of the monomeric complex [(6f)Ca], the solvent molecules were not taken into account. Not surprising in light of the difference of electronegativity of the elements, the charge at C varied between -1.623 (monomer) and -1.847 (dimer) whereas charge at Ca varied between +1.760 (monomer) and +1.821 (dimer). The Ca-C bond was thus described as highly ionic. The calculations with the full dimeric system were carried out, and a slightly reduced charge was calculated at C (-1.778). The NPA charges were also compared to the ones in neutral 6aH 2 and the [Ca(6aH) 2 ] complex. Expectedly the charge at C goes from -1.079 to -1.409 to -1.778 (in 6aH2, [Ca(6aH) 2 ], [Ca(6a)] 2 resp.). The charge at N also increases (-1.474 to -1.580 to -1.665 resp.) upon deprotonation at C. Conversely, the charge at P varies but to a small extent (+1.747 to +1.727 to +1.7...

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Section: Reactivity Of Geminal-dilithio Derivativesmentioning

confidence: 99%

Geminal Dianions Stabilized by Main Group Elements

2019

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“…um and quinolinium rings stabilized through intramolecular NÀSi interaction (Figure 1b). [21b] Silyl-substituted phosphine sulfides have recently been used for generating alkali metal carbenoids (Figure 1c), [22] but the stereochemical implications of a P=Sm oiety on the stabilization of silylium ions have not yet been reported. Eventually,w eg ot inspired by the idea to disclose an ew class of small cationic heterocyclicr ings having a Lewis acidic, chiral, and configurationally stable silicon atom for potentialu se in asymmetric cation-directed or Lewis acidcatalyzed reactions (Figure 1d).…”

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Easy Access to Enantiomerically Pure Heterocyclic Silicon‐Chiral Phosphonium Cations and the Matched/Mismatched Case of Dihydrogen Release

Fontana

Espinosa‐Jalapa

Seidl

et al. 2021

Chemistry A European J

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Phosphonium ions are widely used in preparative organic synthesis and catalysis. The provision of new types of cations that contain both functional and chiral information is a major synthetic challenge and can open up new horizons in asymmetric cation‐directed and Lewis acid catalysis. We discovered an efficient methodology towards new Si‐chiral four‐membered CPSSi* heterocyclic cations. Three synthetic approaches are presented. The stereochemical sequence of anchimerically assisted cation formation with B(C6F5)3 and subsequent hydride addition was fully elucidated and proceeds with excellent preservation of the chiral information at the stereogenic silicon atom. Also the mechanism of dihydrogen release from a protonated hydrosilane was studied in detail by the help of Si‐centered chirality as stereochemical probe. Chemoselectivity switch (dihydrogen release vs. protodesilylation) can easily be achieved through slight modifications of the solvent. A matched/mismatched case was identified and the intermolecularity of this reaction supported by spectroscopic, kinetic, deuterium‐labeling experiments, and quantum chemical calculations.

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“…In case of M/Cl compounds, we were able to showt hat replacemento fL ib yi ts heavier congeners,N aa nd K, resultedi nadistinct stabilization, which allowed selectivity control in carbene-transfer reactions. [16] Given the increased research interest in fluorine chemistry, [17,18] we became interested in the stabilization of M/ Fc arbenoids to pave wayf or further applications of these systems.H erein, we show that even room-temperature-stable systems can be realized employing different stabilizatione ffects.…”

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Taming Metal/Fluorine Carbenoids

Molitor

Feichtner

Gessner

2017

Chemistry A European J

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Although Li/Cl carbenoids are versatile reagents in organic synthesis, the controlled handling of the extremely reactive and labile M/F carbenoids remains a challenge. We now show that even these compounds can be stabilized and isolated in solid state, as well as in solution. Particularly the sodium and potassium compounds exhibit a remarkable stability, thus allowing the first isolation of a room-temperature-stable fluorine carbenoid. Spectroscopic, as well as DFT studies confirmed the pronounced carbenoid character, showing M-F-C interactions with elongated C-F bonds. The different stabilities of the carbenoids was found to originate from the different strength of the M-F interaction. Hence, the lithium compounds are considerably more reactive than their heavier congeners. Reactivity studies showed that the nature of the metal also influences the reactivity, resulting in different selectivity in the addition to thioketones.

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Alkali Metal Carbenoids: A Case of Higher Stability of the Heavier Congeners

Cited by 17 publications

References 84 publications

Geminal Dianions Stabilized by Main Group Elements

Geminal Dianions Stabilized by Main Group Elements

Easy Access to Enantiomerically Pure Heterocyclic Silicon‐Chiral Phosphonium Cations and the Matched/Mismatched Case of Dihydrogen Release

Taming Metal/Fluorine Carbenoids

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