Two new layered vanadium phosphates, (H2NC4H8NH2)[(VO)(PO4)]2 (1) and (H2NC4H8NH2)2[(VO)3(HPO4)2(PO4)2].H2O(2), have been hydrothermally synthesized under similiar conditions. Compound 2 is synthesized from VCl4, H3PO4, piperazine, (n-C4H9)4NOH, and H2O in the mole ratio 1:2.7:2.1:1.2:350 at 200-degrees-C for 70 h and autogeneous pressure. In contrast, the preparation of 2 required the presence of (CH3)PO3H2, such that reaction of VCl4, H3PO4, (CH3)PO3H2, piperazine (n-C4H9)4NOH, and H2O in the mole ratio 1:3.5:1.2:3.3:1.2:390 at 200-degrees-C for 70 h yields 2 in 50% yield, with 1 as the other component. Green plates of compound 1 crystallize in the monoclinic space group P2(1)/c with a = 8.786(2) angstrom, b = 8.257(2) angstrom, c = 8.566(2) angstrom, beta = 11 1.07(3)degrees, V = 579.9(3) angstrom-3, Z = 2, and R = 0.0298 whereas blue plates of 2 crystallize in the noncentrosymmetric orthorhombic space group Pna2(1) with a = 14.631(3) angstrom, b = 8.706(2) angstrom, c = 17.635(4) angstrom, V = 2246.3(1) angstrom-3, Z = 4, and R = 0.0363. Compound 1 has puckered layers containing triangular bipyramidal vanadium(IV) centers. Phosphate 2 has VOPO4-like layers with 1/4 of the V(IV) octahedral sites missing which results in unusual edge-sharing involving half the phosphate tetrahedral with the vanadium octahedra and protonation of the remaining phosphate groups to give HPO4(2-) residues.