Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

The interaction of phosphinetriacetic acid (H₃X) with nickel(II) was examined under various conditions using potentiometric study of solution equilibria, preparation of solid complexes, spectra (electronic and IR) and other methods. In aqueous solutions, the ligand acts as tridentate through the phosphorus atom and two carboxylic groups to form hexacoordinate complexes, NiX^-, NiHX and NiX^4-₂. At 0.8 X/Ni 1.7 and pH 6-8, these complexes are slowly transformed to Ni₃X₂, an insoluble polymeric compound. In non-aqueous solvents, trans-square planar complexes Ni(hal)₂(H₃X₂) (hal = Cl, Br, I) are formed, which contain the ligand coordinated through the phosphorus atom alone. While the solid iodocomplex is also planar, the solid chlorocomplex is hexacoordinated with carbonyl oxygens in axial sites. Both isomeric forms of the bromocomplex were isolated in the solid state.