The novel complex [ Cu (Phen) ( C2O4 ) H2O ]·H2O has been synthesized by K2 [ Cu ( C2O4 )2 ]· 2 H2O and Phen, where Phen = 1,10 -phenanthroline. The crystal structure of the complex has been determined by X - ray diffraction. The crystal belongs to monoclinic system,space group P2(1)/n. The cell parameters are:a =0. 8524(13) nm,b =0. 9764(14) nm,c = 1. 766(3)nm,V = 1. 427(4) nm^3 ,z = 4 ,Dx = 1. 712g. cm^-3 ,μ(MoKa) = 15. 65cm^-1, F(000) = 1268 ,R1= 0. 0435 ,wR2 = 0. 0985. The bend distances of Cu - O and Cu - N are 0. 1...