AN X-RAY-DIFFRACTION STRUCTURAL INVESTIGATION OF ORGANIC COMPLEXONE LIGANDS .17. CRYSTAL AND MOLECULAR-STRUCTURE OF THE DIHYDRO-CHLORIDE SALTS OF ETHYLENE-DIAMINE-N,N'DI-3-PROPIONIC AND ETHYLENEDIAMINE-N,N,N',N'-TETRA-3-PROPIONIC ACIDS AND THE MONBOHYDROBROMIDE SALT OF ETHYLENEDIAMINE-N,N,N',N'-TETRAACETIC ACID MONOHYDRATE

An x-ray diffraction structural analysis was carried out on the cationic forms of three complexones: the dihydrochloride salts C8H18N2O4Cl2 (I) and C14H26N2O8Cl2 (II) and monohydrobromide salt C10H19N2O9Br (III). The data were collected on a diffractometer using lambda-Mo radiation. The structure was solved by the direct method and refined anisotropically for the nonhydrogen atoms and isotropically for the hydrogen atoms by the method of least squares, R = 0.026 (I), 0.040 (II), and 0.044 (III). The crystals of I and II are monoclinic, while the crystals of III are triclinic. I: a = 8.047(2), b = 10.542(2), c = 7.377 angstrom, beta = 95.10(2)-degrees, Z = 2, space group P2(1)/c. II: a = 6.894(2), b = 19.901(5), c = 7.738(3) angstrom, beta = 111.32(2)-degrees, Z = 2, space group P2(1)/c. III: a = 5.458(2), b = 6.889(1), c = 10.631(2) angstrom, alpha = 107.72(1), beta = 107.02(3), gamma = 77.93(2)-degrees, Z = 1, space group P1. Differences were found in the structures of the cationic forms and neutral molecules of these complexones in the crystalline state. Bis-zwitter-ionic structure is lacking in centrosymmetric doubly-charged cations I and II. A strong intermolecular hydrogen bond O(1)..O(1') (2.455(5) angstrom) was found in noncentrosymmetric singly-charged cation III with participation of the proton of dissociated HBr. The cations in the structures of I and II participate only in intermolecular hydrogen bonds, while intramolecular hydrogen bonding is also found in III with the formation of five-membered rings. The structure of these cations depends on the acid properties of the corresponding complexone and composition of the crystals.