Complexes of lanthanide(III) (La-Lu) and Y(III) with 4-methylphthalic acid were prepared and their IR spectra, solubility
in water at 295 K and thermal decomposition were investigated. Rare earth complexes were obtained as solids with a 2:3 ratio
of metal to organic ligand. COO– groups in the prepared complexes act as bidentate chelating and bidentate bridging. During heating they are dehydrated in
one (La-Tm) or twosteps (Yb, Lu and Y) and then decompose to the oxides Ln2O3, CeO2, Pr6O11 and Tb4O7.