The syntheses of the octadentate ligand DOTAM (1,4,7,10-tetrakis(acetamido)-1,4,7,10-cyclododecane) and its complexes with Zn(II), Cd(II), and Ca(II) are described. Crystal structures of [Cd(DOTAM)](ClO4)(2) . 1.5H(2)O (1), [Ca(DOTAM)](ClO4)(2) . 2.5H(2)O (2), and [Zn(DOTAM)](ClO4)(2) . H2O (3) are reported. Crystal data : (1) monoclinic, space group Cc, a = 11.908(2) Angstrom, b = 21.237(3) Angstrom, c = 11.445(2) Angstrom, beta = 102.15(1)degrees; (2) monoclinic, P2(1)/c, a = 14.031(9) Angstrom, b = 11.469(8) Angstrom, c = 17.448 Angstrom, beta = 92.10(1)degrees (3) triclinic, space group , a = 9.490(1) Angstrom, b = 12.464(2) Angstrom, c = 12.998(2) Angstrom, alpha = 99.070(1)degrees, beta = 107.67(1)degrees, and gamma = 108.24(1)degrees. There is an unusual distortion in the coordination geometry of the complexes. There are two sets of metal-to-oxygen bond lengths for each complex; Zn(II) has two oxygens, placed opposite each other in the approximately square arrangement defined by the four oxygen donor atoms at about 2.19 Angstrom and two at 3.23 Angstrom, Cd(II) has two at 2.34 and two at 2.64 Angstrom, and Ca(II) has two at 2.40 Angstrom and two at 2.42 Angstrom.