Rb2Co3(H2O)2[B4P6O24(OH)2]: Ein Borophosphat mit ‐Tetraeder‐Anionenteilstruktur und Oktaeder‐Trimeren (CoO12(H2O)2)

Rb₂Co₃(H₂O)₂B₄P₆O₂₄(OH)₂]: A Borophosphate with ‐Tetrahedral Anionic Partial Structure and Trimers of Octahedra (Co O₁₂(H₂O)₂) Rb₂Co₃(H₂O)₂B₄P₆O₂₄(OH)₂] is formed under mild hydrothermal conditions (T = 165 °C) from mixtures of RbOH_(aq), CoCl₂, H₃BO₃, and H₃PO₄ (molar ratio 1 : 1 : 1 : 2). The crystal structure (orthorhombic system) was solved by X‐ray single crystal methods (space group Pbca, No. 61; R‐values (all data): R1 = 0.0699, wR2 = 0.0878): a = 950.1(1) pm, b = 1227.2(2) pm, c = 2007.4(2) pm; Z = 4. The anionic partial structure consists of tetrahedral B₄P₆O₂₄(OH)₂^8–] layers, which contain three‐ and nine‐membered rings. Co^II is octahedrally coordinated by oxygen and oxygen and H₂O ligands, respectively (coordination octahedra CoO₆ and CoO₄(H₂O)₂). Three adjacent coordination octahedra are condensed via common edges to form trimeric units (CoO₁₂(H₂O)₂). The oxidation state +2 of cobalt was confirmed by magnetic measurements. The octahedral trimers are quasi‐isolated. No long‐range magnetic ordering occurs down to 2 K. Rb⁺ is disordered over three crystallographically independent sites within channels of the structure running parallel 010]; the coordination sphere of Rb⁺ is formed by nine oxygen species of the tetrahedral layers, one OH group and one H₂O molecule.