title: 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.
authors.affiliation: State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian, 361005, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Kartik Chandra
authors.initials: KC
authors.lastname: Mondal
authors.forename: Herbert W
authors.initials: HW
authors.lastname: Roesky
authors.forename: Hongping
authors.initials: H
authors.lastname: Zhu
authors.forename: Peter
authors.initials: P
authors.lastname: Stollberg
authors.forename: Regine
authors.initials: R
authors.lastname: Herbst-Irmer
authors.forename: Dietmar
authors.initials: D
authors.lastname: Stalke
authors.forename: Diego M
authors.initials: DM
authors.lastname: Andrada