[en] Two layered indium oxalates, In(C₂O₄)_2.5(C₃N₂H₁₂)(H₂O)₃, I, and In(C₂O₄)_1.5(H₂O)₃, II, have been hydrothermally synthesized. In I, the linkage between indium and oxalate units gives rise to a sheet with a rectangular 12-membered aperture (six indium atoms and six oxalate units). Indium atom of II has an unusual pentagonal bipyramidal coordination arrangement. The connectivity between indium and oxalate units forms a neutral puckered layer with 12- (along a-axis) and eight-membered (along b-axis) apertures. Crystal data for these two indium oxalates are as follows: I, triclinic, space group: P-1 (No. 2), a=8.725(3) A, b=9.170(3) A, c=9.901(3) A, α=98.101(4) deg. , β=97.068(4) deg. , γ=102.403(4) deg. , V=756.3(4) A³, Z=2, M=463.0(5), ρ_calc=2.042 g/cm³, R₁=0.0377, wR₂=0.0834. II, monoclinic, space group: P2₁/c (No. 14), a=10.203(5) A, b=6.638(1) A, c=11.152(7) A, β=95.649(4) deg. , V=751.7(4)A³, Z=4, M=300.9(0), ρ_calc=2.659 g/cm³, R₁=0.0229, wR₂=0.0488. TG analyses indicate the water molecules of I can be removed at 150 deg. C. The dehydrated product retains structural integrity