AbstractWe have investigated the coordination of alkanide and alkynide anions to the coordinatively unsaturated aluminium atoms of the methylene‐bridged dialuminium compound R2Al‐CH2‐AlR2 [1, R = CH(SiMe3)2]. Treatment of 1 with the corresponding lithium derivatives in the presence of a small excess of TMEN (TMEN = tetramethylethylenediamine) yielded mono‐adducts [M]+[R2Al‐CH2‐AlR2R']– [2a, M = Li(TMEN)2, R' = Me; 2b, M = Li(TMEN)2, R' = n‐Bu; 3a, M = Li(TMEN)2, R' = C≡C‐SiMe3; 3b, M = Li(TMEN)2, R' = C≡C‐t‐Bu; 3d, M = Li(DME)3, R' = C≡C‐Ph; 3e, M = Li(TMEN)2, R' = C≡C‐PPh2)] and bis‐adducts [Li(TMEN)2]+[LiCH2(AlR2R')2]– [4a, R' = C≡C‐CH2‐NEt2; 4b, R' = C≡C‐t‐Bu]. In the solid state the mono‐adducts have clearly separated coordinatively saturated (coordination number four) and unsaturated aluminium atoms (coordination number three). In solution the groups R' show a fast exchange between both aluminium atoms as evident from the room temperature NMR spectra that showed in most cases equivalent CH(SiMe3)2 groups despite different coordination spheres of the metal atoms. Only 2b gave the expected splitting of resonances at ambient temperature, while cooling was required to prevent the dynamic process for 3a. The dialkynide 4a has a unique molecular structure with one of the lithium cations bonded to the α‐carbon atoms of the alkynido ligands and to the carbon atom of the methylene bridge which is five‐coordinate with a distorted trigonal bipyramidal coordination sphere.