Structures of sodium zinc nitrilotriacetate monohydrate (173 K) and disodium hydrogen nitrilotriacetate (293 K)

NaZn(C6H6NO6).H20: Mr =295"44, orthorhombic, P212121, a = 7.869 (4), b =9.783 (6), c = 12.292 (6) A,, V = 946-3 A, 3, Z = 4, Dx = 2.07 gcm -3, A (So Kc~) = 0.71073A,, /z=27.4cm -I Final R=0.052 for 859 unique reflections. The nitrilotriacetate ion is coordinated to the Zn 2+ ion in a tetradentate fashion. The remaining two octahedral sites about the Zn 2÷ ion are occupied by O atoms of different nitrilotriacetate ions. A comparison of the structure with other published structures identifies a common geometry, termed the 'butterfly' geometry, for transition-metal complexes with nitrilotriacetate ligands. The Na ÷ ions bridge the nitrilotriacetatozinc ions thereby holding the structure intact. The water molecule is coordinated to the five-coordinate Na ÷ ion. Na2(C6H7NO6): M, = 235-10, cubic, P213, a = 9-417 (2) ~, V = 835.1 A, 3, Z = 4, Dx = 1.87 g cm -3, A(Cu K6)= 1.54178 ~, p.=23.3 cm -l Final R = 0.034 for 208 unique reflections. The structure is the first observation of the zwitterionic form of the nitrilotriacetate ion as a tridentate chelating ion. The [C6H7NO6Na]- ions are linked together by a complex network of bridging Na ÷ ions. The differences in the coordination of the nitrilotriacetate ligand to the metal ions in these structures illustrate the versatile, multidentate chelating capabilities of the ligand.