Reaktionen des metalloiden Clusteranions {Ge9[Si(SiMe3)3]3}– in der Gasphase. Oxidations‐ und Reduktionsschritte geben Einblicke in den Bereich zwischen metalloiden Clustern und Zintl‐Ionen

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AbstractThe cluster anion {Ge9[Si(SiMe3)3]3}– (1) is transferred intact into the gas phase via the electro spray method. Subsequently the fragmentation of 1 after resonant excitation as well as the oxidation reaction with O2 and Cl2 are investigated in an FT‐ICR mass spectrometer (Fourier Transform Ion Cyclotron Resonance). Unlike former results with off‐resonant excitation the fragmentation leads mainly to the end‐product Ge9–. Moreover, applying an on‐resonant excitation the dissociation experiment can be quantified; 2.0 ± 0.15 eV (193 ± 15kJ·mol–1) for the elimination of the first two ligands and 2.7 ± 0.15 eV (261 ± 15 kJ·mol–1) for all ligands, respectively. Particular attention is turned on the first step, where sterically encumbered Si2(SiMe3)6 molecules are formed in a concerted reaction. This result, which is also important for elemental reactions on metal surfaces in catalyses, is based on experimentally determined threshold energies, DFT calculations and calculations on the lifetime of the involved species., In contrast to the high reactivity of crystalline 1·Li(THF)4, gaseous 1 is inert against oxygen. The analogy to recently published spin forbidden reactions of Al13– with O2 hints to a general importance of spin conversion during gas phase reactions of larger cluster molecules. The oxidation of 1 with Cl2 proceeds through different reaction channels. DFT calculations give a first insight on the complex primary oxidation steps. These calculations also reveal that the delocalized bonding situation in the Ge9 core is distorted upon oxidation. This result together with the dissociation experiments shed more light on differences and similarities between metalloid clusters and Zintl ions.