Ga 19(C(SiMe 3) 3) 6− as a precursor for pure and silicon-doped gallium clusters: a mass spectrometric study of a Ga 13− and a Ga 12Si − anion

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The metalloid cluster [Ga 19(C(SiMe 3) 3) 6][Li 2Br(THF) 6] was studied by Fourier-transform ion cyclotron resonance-mass spectrometry (FT/ICR-MS). The spectrum obtained by laser desorption ionization (LDI) is dominated by pure gallium cluster anions Ga n − with n ranging up to 50 and mixed gallium–silicon cluster anions Ga n Si −, Ga n Si 2 −, and Ga n Si 3 − with n ranging up to 43. A maximum of the cluster abundance is observed for Ga 13 − and Ga 12Si −. These experimental results exhibit for the first time the formation of large pure and silicon-doped gallium clusters starting from a molecular compound. They are discussed in terms of the precursor’s structure and the simplified predictions of the jellium model. DFT calculations were employed to further evaluate the electronic properties of these anionic clusters, the results of which show that Ga 13 − favors a regular bicapped pentagonal prism (D 5h) as well as Ga 12Si −, Si being located in the center of the cluster.