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    Bildung Stabiler All-Silicium Varianten von 1,3-Cyclobutandiyl im Gleichgewicht
    (Wiley-Blackwell, 2020) Yıldız, Cem Burak; Leszczyñska, Kinga I.; González-Gallardo, Sandra; Zimmer, Michael; Azizoğlu, Akın; Biskup, Till; Kay, Christopher W.M.; Hüch, Volker; Rzepa, Henry S.; Scheschkewitz, David
    Hauptgruppenanaloga von 1,3-Cyclobutandiylen faszinieren mit ihrer einzigartigen Reaktivitt und ihren elektronischen Eigenschaften. Bisher sind allerdings nur heteronukleare Vertreter isoliert worden. Wir berichten hier ber die Isolierung und Charakterisierung von All-Silicium-1,3-Cyclobutandiylen als stabile Singulettspezies mit geschlossenschaliger Konfiguration aus den reversiblen Reaktionen von Cyclotrisilen c-Si3Tip4 (Tip = 2,4,6-Triisopropylphenyl) mit den N-heterocyclischen Silylenen c-[(CR2CH2)(NtBu)2]Si: (R = H oder Methyl) mit gesttigten Grundger sten. Bei erhçhten Temperaturen werden aus diesen Gleichgewichtsmischungen Tetrasilacyclobutene erhalten. Die analoge Reaktion mit dem ungesttigten N-heterocyclischen Silylen c-(CH)2- (NtBu)2Si: verluft direkt zum entsprechenden Tetrasilacyclobuten ohne Nachweis des angenommenen 1,3-Cyclobutandiyl-Zwischenprodukts
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    Dimerization of a marginally stable disilenyl germylene to tricyclic systems: evidence for reversible NHC-coordination
    (Royal Soc Chemistry, 2016) Nieder, David; Yıldız, Cem Burak; Jana, Anukul; Zimmer, Michael; Huch, Volker; Scheschkewitz, David
    Tetrasiladigermatricyclohexanes in two isomeric forms (chair and doubly-bridged tetrahedron) are obtained by the reaction of MeLi with an alpha-chlorosilyl functionalized NHC-stabilized silagermenylidene. Si-29 NMR at low temperature proves the initial formation of a monomeric NHC-adduct of a disilenyl germylene followed by cyclisation to the isomeric heavy cyclopropene. Addition of an excess of NHC stabilizes the both intermediates and demonstrates the reversibility of rate-determining initial equilibria involving NHC dissociation. Finally, a mixture of two isomeric tricyclic Si4Ge2 species is obtained: at elevated temperature the chair isomer converts to the doubly edge-bridged tetrahedron.
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    Equilibrium Formation of Stable All-Silicon Versions of 1,3-Cyclobutanediyl
    (Wiley-VCH Verlag, 2020) Yıldız, Cem Burak; Leszczyñska, Kinga I.; González-Gallardo, Sandra; Zimmer, Michael; Azizoğlu, Akın; Biskup, Till; Kay, Christopher; Hüch, Volker; Rzepa, Henry S.; Scheschkewitz, David
    Main group analogues of cyclobutane-1,3-diyls are fascinating due to their unique reactivity and electronic properties. So far only heteronuclear examples have been isolated. Here we report the isolation and characterization of all-silicon 1,3-cyclobutanediyls as stable closed-shell singlet species from the reversible reactions of cyclotrisilene c-Si3Tip4 (Tip=2,4,6-triisopropylphenyl) with the N-heterocyclic silylenes c-[(CR2CH2)(NtBu)2]Si: (R=H or methyl) with saturated backbones. At elevated temperatures, tetrasilacyclobutenes are obtained from these equilibrium mixtures. The corresponding reaction with the unsaturated N-heterocyclic silylene c-(CH)2(NtBu)2Si: proceeds directly to the corresponding tetrasilacyclobutene without detection of the assumed 1,3-cyclobutanediyl intermediate.
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    Reactivity enhancement of a diphosphene by reversible N-heterocyclic carbene coordination
    (Royal Society of Chemistry, 2018) Dhara, Debabrata; Kalita, Pankaj; Mondal, Subhadip; Narayanan, Ramakirushnan Suriya; Mote, Kaustubh R.; Huch, Volker; Zimmer, Michael; Yıldız, Cem Burak; Scheschkewitz, David; Chandrasekhar, Vadapalli; Jana, Ankul
    Diphosphene TerMesP = PTerMes (1; TerMes = 2,6-Mes2C6H3; Mes = 2,4,6-Me3C6H2) and NHCMe42 (NHCMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene) exist in an equilibrium mixture with the NHCMe4-coordinated diphosphene 3. While uncoordinated 1 is inert to hydrolysis, the NHC adduct 3 readily undergoes hydrolysis to afford a phosphino-substituted phosphine oxide with the liberation of NHCMe4. On this basis, conditions suitable for the catalytic use of NHCMe4 were identified. Similarly, while the hydrogenation of free diphosphene 1 with H3N·BH3 is very slow, 3 reacts instantaneously with H3N·BH3 at room temperature to afford a dihydrodiphosphane. © 2018 The Royal Society of Chemistry.