New binuclear vanadium(III) and (IV) squarate species:: synthesis, structure and characterization of [V(OH)(H2O)2(C4O4)]2•2H2 and (NH4)[(VO) 2(OH)(C4O4)2(H2O)3]•3H2O

Two new vanadium squarates have been synthesized, characterized by infrared and thermal behavior and their structures determined by single crystal X-ray diffraction. Both structures are made of discrete, binuclear vanadium entity but in 1, [V(OH)(H2O)(2)(C4O4)](2)(.)2H(2)O the vanadium atom is trivalent and the entity is neutral while in 2, (NH4)[(VO)(2)(OH)(C4O4)(2) (H2O)(3)](.)3H(2)O, the vanadium atom is tetravalent and the entity is negatively charged, balanced by the presence of one ammonium ion. Both molecular anions are bridged by two terminal mu(2) squarate ligands. 1 crystallizes in the triclinic system, space group P-1, with lattice constants a = 7.5112(10) Angstrom, b = 7.5603(8) Angstrom, c = 8.2185(8) Angstrom, alpha = 106.904(8)degrees, beta = 94.510(10)degrees, gamma = 113.984(9)degrees while 2 crystallizes in the monoclinic system, space group C2/c, with a = 14.9340(15) Angstrom, b = 6.4900(9) Angstrom, c = 17.9590(19) Angstrom and beta = 97.927(12)degrees. From the magnetic point of view, V(III) binuclear species show ferromagnetic interactions at low temperatures. However, no anomalies pointing to magnetic ordering are observed down to 2K. (C) 2003 Elsevier Inc. All rights reserved.