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Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Regiodiscriminating Reactivity of Isolable NHC-Coordinated Disilenyl Germylene and Its Cyclic Isomer
David Nieder1, Volker Huch1, Cem B Yildiz2
1Krupp-Chair of General and Inorganic Chemistry, Saarland University , 66125 Saarbrücken, Germany.
Abstract:
An isolable NHC-coordinated disilenyl germylene R2Si═SiR-GePh·NHCiPrMe (5b: R = 2,4,6-triisopropylphenyl, NHCiPrMe = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) is obtained from the reaction of the α-chloro silyl functionalized heavier vinylidene analogue R2(Cl)Si-RSi═Ge·NHCiPrMe 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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