An isolable NHC-coordinated disilenyl germylene RSi═SiR-GePh·NHC (5b: R = 2,4,6-triisopropylphenyl, NHC = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) is obtained from the reaction of the α-chloro silyl functionalized heavier vinylidene analogue R(Cl)Si-RSi═Ge·NHC with phenyllithium. The disilenyl germylene 5b isomerizes at 40 °C to the NHC-adduct of the corresponding heavier cyclopropylidene analogue 6b. Both 5b and 6b display near perfect regiodiscrimination in their reactions with phenylacetylene and xylyl isocyanide, affording in the case of each reagent two different regioisomers of NHC-coordinated cyclic germylenes. DFT calculations reveal that the Si═Si bond accounts for the high reactivity of 5b even at low temperature while in the case of cyclic 6b the low-valent germanium center requires a considerable thermal activation.
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Regiodiscriminating Reactivity of Isolable NHC-Coordinated Disilenyl Germylene and Its Cyclic Isomer.
J Am Chem Soc
October 2016
Krupp-Chair of General and Inorganic Chemistry, Saarland University, 66125 Saarbrücken, Germany.
An isolable NHC-coordinated disilenyl germylene RSi═SiR-GePh·NHC (5b: R = 2,4,6-triisopropylphenyl, NHC = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) is obtained from the reaction of the α-chloro silyl functionalized heavier vinylidene analogue R(Cl)Si-RSi═Ge·NHC with phenyllithium. The disilenyl germylene 5b isomerizes at 40 °C to the NHC-adduct of the corresponding heavier cyclopropylidene analogue 6b. Both 5b and 6b display near perfect regiodiscrimination in their reactions with phenylacetylene and xylyl isocyanide, affording in the case of each reagent two different regioisomers of NHC-coordinated cyclic germylenes.
View Article and Find Full Text PDFDimerization of a marginally stable disilenyl germylene to tricyclic systems: evidence for reversible NHC-coordination.
Chem Commun (Camb)
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Krupp-Chair of General and Inorganic Chemistry, Saarland University, 66125 Saarbrücken, Germany.
Tetrasiladigermatricyclohexanes in two isomeric forms (chair and doubly-bridged tetrahedron) are obtained by the reaction of MeLi with an α-chlorosilyl functionalized NHC-stabilized silagermenylidene. (29)Si 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.
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