Abstract: The title complex was synthesized and characterized by elemental analysis and FT-IR spectrometry. The crystal of the complex, determined by X-ray diffraction method, belongsto monoclinic with space group C2/c and cell parameters a=19.358(8)Å b=11.841(4)Å,c=21.272(8)Å, β=100.55(3) and Z=4.Dimethyl phosphates coordinate with lanthanums for-ming a special structure of alternate two-four O-P-O bridges. Trimethyl phosphates arearranged on tho two sides of the eight-membered rings of the double bridges.

Key words: Lanthanum complex, Tris-(dimethyl phosphate), Trimethyl phosphate, Crystal structure, Vibration spectrum