Acyclic Germylones: Congeners of Allenes with a Central Germanium Atom

Abstract

The cyclic alkyl(amino) carbene (cAAC:)-stabilized acyclic germylones (Me2-cAAC:)2Ge (1) and (Cy2-cAAC:)2Ge (2) were prepared utilizing a one-pot synthesis of GeCl2(dioxane), cAAC:, and KC8 in a 1:2:2.1 molar ratio. Dark green crystals of compounds 1 and 2 were produced in 75 and 70% yields, respectively. The reported methods for the preparation of the corresponding silicon compounds turned out to be not applicable in the case of germanium. The single-crystal X-ray structures of 1 and 2 feature the C-Ge-C bent backbone, which possesses a three-center two-electron π-bond system. Compounds 1 and 2 are the first acyclic germylones containing each one germanium atom and two cAAC: molecules. EPR measurements on compounds 1 and 2 confirmed the singlet spin ground state. DFT calculations on 1/2 revealed that the singlet ground state is more stable by ~16 to 18 kcal mol(-1) than that of the triplet state. First and second proton affinity values were theoretically calculated to be of 265.8 (1)/267.1 (2) and 180.4 (1)/183.8 (2) kcal mol(-1), respectively. Further calculations, which were performed at different levels suggest a singlet diradicaloid character of 1 and 2. The TD-DFT calculations exhibit an absorption band at ~655 nm in n-hexane solution that originates from the diradicaloid character of germylones 1 and 2.

Experimental Charge Density Study of a Silylone

“…There are small but significant differences in the bond lengths of Si1 À C1 (1.8454 (2) Figure 5). [23,12] Thus this might be attributed to packing effects. [23] However, compounds with dimethyl groups instead of the cyclohexyl group do not show significant differences in these values, both in the silylone and the germylone.…”

Stabile Heterocyclopentan‐1,3‐diyle

“…[(m-NTer)P] 2 (1) 25 %). [18,19,[31][32][33][34] Weiterhin belegen die Besetzungszahlen der natürlichen Orbitale (HOMO: 1.44 e, LUMO: 0.56 e) deutlich den offenschaligen Singulett-Biradikalcharakter. [35] Als Beispiel für die Reaktivität des neuen Cyclopentandiyls wurde die Reaktion mit einem Phosphaalkin untersucht (Schema 3).…”

Anorganische Chemie 2013

“…Das Homo ist hingegen ein π‐Orbital mit dem ebenfalls größten Koeffizienten am zentralen Siliciumatom 49. Ähnliches findet man auch für die homologe Germaniumverbindung, wobei das Homo allerdings stärker am Germanium zentriert ist 50. Cyclische Sila‐51 und Germadicarbene52 wie (19) lassen sich basierend auf einem methylenverbrückten, N‐heterocyclischen Dicarben darstellen.…”