A novel germanium(IV) oxalate complex: [Ge(OH)2(C2O4)2]2−

Two crystalline compounds, X · [Ge(OH)2(C2O4)2]· n(H2O) [where image and n = 1 for compound I, and image and n = 2 for II], were synthesised using hydrothermal synthetic approach and characterised structurally using single-crystal X-ray diffraction, vibrational spectroscopy (FT-IR and FT-Raman), thermogravimetric analysis (TGA) and CHN elemental composition. The crystalline compounds contain a novel anionic complex [Ge(OH)2(C2O4)2]2−, which co-crystallises with organic cations (piperazinium in I, and 4,4′-bipyridinium in II) and water molecules of crystallisation. These chemical moieties are involved in extensive three-dimensional (3D) hydrogen bonding networks composed of strong and highly directional O–H⋯O and N–H⋯O interactions.