A new series of chromium(II)-alkylphosphonates, Cr[RPO3]·H2O (R = CH3, C2H5), and chromium(II) ethylenebis(phosphonate), Cr2[O3P−(CH2)2−PO3]·3H2O, have been synthesized by reaction of CrCl2 and the corresponding phosphonic acid in water in the presence of urea. The (2-aminoethyl)phosphonic acid reacts with CrCl2 to give an unexpected compound of formula Cr[H3N−(CH2)2−PO3(Cl)]. All the compounds are sensitive to the air, except for the latter one. They were characterized by X-ray powder diffraction, thermogravimetry, and UV−visible and infrared spectroscopy, and their magnetic properties were studied by a SQUID magnetometer. The metal ion is in the high-spin d4 configuration, and it appears to have an octahedral coordination. Cr[CH3PO3]·H2O behaves as a “weak” ferromagnet, with a Nèel temperature of TN = 35 K, and it represents an example of an unusual kind of molecular-based magnetic material, having a finite zero-field magnetization. The thermal variation of the magnetic susceptibility of Cr2[O3P−(CH2)2−PO3]·3H2O follows the Curie−Weiss law, with a large negative Weiss constant of θ = −73 K. Below 100 K, the susceptibility increases until a peak at TN = 15 K is observed, and this is associated to the three-dimensional antiferromagnetic order. Cr[H3N−(CH2)2PO3(Cl)] is paramagnetic down to 5 K.

The formation constants of the binary and ternary complexes formed in solution of Pb2+, Co2+, Ni2+, Cu2+, Cd2+, Ce3+ and UO22+ with N-(2-acetamido)-iminodiacetic acid (H2ADA) and salicylic acid derivatives [thiosalicylic (TSA) and 3,5-dinitrosalicylic acid (DNSA)] have been determined pH-metrically at t = 25 ± 0.1 °C and ionic strength μ = 0.1 mol dm-3 (KNO3) The stability of the different complexes formed are discussed in terms of the nature of the ligands and metalions. The mixed ligand complexes of the type [M2+(ADA)(TSA)] (M2+ = Co2+, Ni2+, Cu2+) were synthesized and characterized.