This work comprehensively investigated the coordination chemistry of a -dentate neutral amine ligand, namely, --(2--diethylaminoethyl)-1,4,7-triaza-cyclononane (DETAN), with group-1 metal cations (Li, Na, K, Rb, Cs). Versatile coordination modes were observed, from four-coordinate trigonal pyramidal to six-coordinate trigonal prismatic, depending on the metal ionic radii and metal's substituent. For comparison, the coordination chemistry of a -dentate -[2-(dimethylamino)ethyl]amine (MeTren) ligand was also studied. This work defines the available coordination modes of two multidentate amine ligands (DETAN and MeTren), guiding future applications of these ligands for pursuing highly reactive and elusive s-block and rare-earth metal complexes.