Abstract: A four-coordinated CuII complex with a novel trimers of oxalate ligand(Cu(L)2(H2L)(C5H6)2,where H2L = oxalic acid) has been synthesized and characterized by elemental analyses and X-ray diffraction techniques.The crystal structure of this complex reveals that the CuII center has a CuO4 parallelogram plane environment and CuII locates in the center of the parallelogram.Furthermore,two Cu(L)22-layers adjacent to pyridine bridge form 3-D networks through intermolecular C—H…O hydrogen-bonded interactions.