Restricted accessResearch articleFirst published online 2005-10
Understanding of the Structure,Bonding,Formation and Decomposition of Metalloid Aluminum Clusters—A Fourier Transform Ion Cyclotron Resonance Study of Solid AlCp*
The investigation of the tetrahedral Al4Cp*4 cluster with a Fourier transform ion cyclotron resonance mass spectrometry using laser desorption/ionization as the ionization method results in a couple of aluminum cluster compounds AlxCp*+y (x>y) with up to eight aluminum atoms. MSn experiments are performed in order to understand the formation and reactivity of the different species. Quantum chemical calculations of the structure and energy for all compounds identified complete this study.
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From the quantum chemical calculation results, that the isomer with the aluminum atoms on each side of the Cp* group, Al-Cp*-Al+, is slightly lower in energy than the one with the aluminum atoms on one side of the Cp* group, Al-Al-Cp*+, i.e. 30 kJ mol−1. However, concerning the uncertainties in quantum chemical calculations, the latter is presented in Figure 2 because the formation of Al-Cp*-Al+, starting from Al4Cp*+4 with its central Al4 tetramer, is hard to explain.
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The resolution and accuracy of spectra obtained in FT-ICR mass spectrometry are good enough to decide between a cation AlxCp*+y and one being comparable in mass with a corresponding formula, Alx+5Cp*+y-1. For example, the cation Alx+5Cp*+y-1 exhibits a mass of 351.179 au whereas the cation Al8Cp*+ with 350.969 au is just slightly lower in mass. During the experiments, both compounds could be identified and properly attributed.
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