MII(C4H12N2)[B2P3O12(OH)] (MII = Co,Zn): Synthesis and Crystal Structure of Novel Open Framework Borophosphates

Two novel borophosphates, M^II(C₄H₁₂N₂)B₂P₃O₁₂(OH)] (M^II = Co, Zn), exhibiting open frameworks, have been synthesized by hydrothermal reactions (T = 165 °C). The crystal structures of the isotypic compounds have been determined both at 293 K (orthorhombic, Ima2 (no. 46), Z = 4; M^II = Co: a = 12.4635(4) Å, b = 9.4021(4) Å, c = 11.4513(5) Å, V = 1341.90 ų, R₁ = 0.0202, wR₂ = 0.0452, 2225 observed reflections with I > 2σ(I); M^II = Zn: a = 12.4110(9) Å, b = 9.4550(5) Å, c = 11.4592(4) Å, V = 1344.69 ų, R₁ = 0.0621, wR₂ = 0.0926, 1497 observed reflections with I > 2σ(I)). Distorted CoO₆‐octahedra and ZnO₅‐square‐pyramids, respectively, share common oxygen‐corners with BO₄‐, PO₄‐ and (HO)PO₃‐tetrahedra. The tetrahedral groups are linked via common corners to form infinite loop‐branched borophosphate chains B₂P₃O₁₂(OH)^4–]. The open framework of M^II‐coordination polyhedra and tetrahedral borophosphate chains contains a three‐dimensional system of interconnected structural channels running along 100], 011] and 011], respectively, which are occupied by di‐protonated piperazinium ions.