The reactivity of aluminum cluster anions with tetrakis(dimethylamino)ethylene (TDMAE) has been studied using mass spectrometry. All aluminum cluster anions, regardless of their size, disappeared from the mass spectrum upon introduction of TDMAE, leaving behind the single anionic reaction product, [Al(TDMAE)]. The combination of anionic photoelectron spectroscopy and density functional theory was then employed to probe the structure of this anion. Contrary to the pi-complex structure known in Al-alkene systems, [Al(TDMAE)] was found to prefer a 2 eV more stable geometry in which Al inserted into one of the C-N bonds in TDMAE. (C) 2009 Elsevier B.V. All rights reserved.