Abstract: The preparation of a number of complexes of LnCl₃(Ln = Nd,Sm,Eu,Gd,Dy, Tb, Er and Yb) with dimethyl sulfoxide is reported.The structures of some of them have been elucidated on the basis of infrared spectra,nmr spectra, thermoana-lysis, X-ray diffraction and chemical analysis.It appears that sulfur is the donor atom in all cases reported.From the results of single crystal X-ray diffraction analysis,it shows that the cell parameters for the species of Nd and Tb are.α= 9.7998, b= 10.1458, C=14.7505 α = 93.0376, β= 100.2652, γ = 99.6542; α= 9.7083, b = 10.1216, c = 14.6725 α = 93.3927, β = 99.8257, γ = 100.1570 respectively.Both of them are triclinic.The structure for Nd species is proposed as a distorted triangle dodecahedron.There are two lanthanide ions, ten DMSO, eight water molecules and six chloride ions in each cell.All the DMSOare coplanar and coordinated with Ln ion through oxygen atom.Among the eight water molecules, six of them are coordinated with center ions, the other two and six chloride ions are in orderly state.