Crystal structure of iodanilic acid

C6I2O4H2, iodanilic acid, Mr = 391.89, monoclinic, P21/c, a = 1477.5(3), b = 493.6(2), c = 1339.5(2) pm, β = 113.53(1)°, V = 895.66 · 106 pm3, Z = 4, Dx = 2.91 g/cm3, Dm = 2.87 g/cm3, MoKα, γ = 71.07 pm, μ = 68.95 cm−1, F(000) = 704, T = 293 K, R = 3.64%, Rw = 2.8%, Rg = 2.5% for 1601 used unique reflections. The structure was refined by least-squares methods using single crystal X-ray diffractometer data. The molecules of C6I2O4H2 are interlinked by intermolecular hydrogen bonds to form layers. Intramolecular hydrogen bonding has to be taken into account as well.