Hydrothermal synthesis of transition metal oxide containing organic-inorganic hybrid materials has attracted great attention recently. Two novel organic-inorganic hybrid materials (4,4ʼ-bipy)3[HPW12O39] and [Cu(4,4ʼ-bipy)4][HPW12O40] were hydrothermally synthesized as green and purple crystals respectively, from the reaction of Na6[H2W12O40], CuCl2.2H2O, 4,4ʼ- bipyridine and H3PO4 in a 23 ml autoclave at 170°C for 72 hours. The compound (4,4ʼ-bipy)3[HPW12O39] crystallizes in the space group P21/n of the monoclinic system with four formula units in a cell with dimensions a = 13.503(3) Å, b = 26.726(5) Å, c =15.169(3) Å and V = 5397.3(19) Å3. [Cu(4,4ʼ-bipy)4][HPW12O40] crystallizes in the space group Pbcn of the tetragonal system with eight formula units in a cell of dimensions a = 20.236(4) Å, b = 25.635(5) Å, c = 20.236(4) Å; V = 10497(4) Å3 . Both of the compounds are Keggin polyoxometalate structures. (4,4ʼ-bipy)3[HPW12O39] contains free 4,4ʼ-bipy groups among the clusters while in [Cu(4,4ʼ-bipy)4][HPW12O40] 4,4ʼ-bipy ligands are coordinated to Cu2+ ions. A novel compound (H2NC4H8NH2)[(VO)2(PO4)2] was synthesized hydrothermally from the reaction of NaVO3, V2O5, ethylenediamine and H3PO4 at 170 C for 72 hours. The compound crystallizes in the space group P-1 of the trigonal system with five formula units in a cell of dimensions a= 6.3345(13) Å, b= 6.3353(13) Å, c= 15.940(3) Å, V=639.6(2) Å3. (H2NC4H8NH2)[(VO)2(PO4)2] displays a layered structure with protonated piperazine groups between layers. In addition to the novel compounds, several known compounds were synthesized as well. Blue crystals of (VO)(H2PO4)2 were obtained hydrothermally from the reaction of NaVO3, ethylenediamine and H3PO4 at 170C for 72 hours (C5NH6)4.5(H3O)1.5[P2W18O62] , a known compound also, was synthesized from the reaction of Na2WO4 .2H2O, CuCl2.2H2O, pyridine and H3PO4 at 170C for 72 hours.