(Chemical Equation Presented) The beauty of symmetry: The Si 2(CH3)7+ ion can be observed under the low pressures used in Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. The optimized geometry of the ion, as determined from theoretical calculations and FT-ICR experimental results, reveals a C 3h-symmetric structure, in which a planar CH3 group is symmetrically bonded to two eclipsed Si(CH3)3 moieties (see picture; Si blue, C dark gray, H pale gray). © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.