Novel complexes of Co2+, Ni2+, and Cu2+ with N-(phosphonomethyl)aminosuccinic acidSynthesis, thermal, spectroscopic, and coordination aspects

Complexes of Co2+, Ni2+, and Cu2+ with N-(phosphonomethyl)aminosuccinic acid (H4PMAS) of general formula Na2MPMAS·nH2O [M=Co(II), Ni(II), Cu(II), n—number of water molecules] were synthesized. Based on interpretation of diffusion reflectance spectroscopy, structure of all complexes is based on distorted octahedral. Analysis of IR spectra of Co(II), Ni(II), and Cu(II) N-(phosphonomethyl)aminosuccinates demonstrated that metal ions are coordinated to the ligand through nitrogen atom of the imino group, oxygen atoms of the α- and β-carboxyl groups as well as oxygen atom of the phosphonic group of the H4PMAS. We demonstrated that thermal stability of complexes increases in sequence Cu(II) < Ni(II) < Co(II), obviously as a result of change over from the dimeric to polymeric character of the initial complex. Complete decomposition of ligand occurs at these temperatures and is accompanied by release of H2O, CO2, and NO2. The final products of thermal decomposition of the complexes are mixtures of oxides and phosphates of respective metals.