Abstract: In this paper, the metathetical reaction involving rare earth carbonates and propenoic acid has been successful in the preparation of Ln(C₃H₃O₂)₃·H₂O(Ln = La, Ce,……Yb and Y). With the composition determined by chemicalanalysis, the experimental data obtained from a number of modern physical and spectroscopic studies of IR, UV, and 1HNMRprovided powerful evidence for the synthesis of new complexes. Their properties and structure have been discussed as well.