The new high-pressure borate hydrate Cu3B6O12 · H2O

The new compound Cu3B6O12 · H2O, synthesized under high-pressure/high-temperature conditions of 7.5 GPa and 700 °C in a Walker-type multianvil apparatus, possesses a structure similar to CuB2O4 (3 × CuB2O4 = Cu3B6O12). Via the high-pressure technique, it was possible to incorporate water molecules into the structure, leading to a symmetry reduction compared to the water free compound (I  4¯2d → Fdd2). Cu3B6O12 · H2O crystallizes in the orthorhombic space group Fdd2 (Z = 8) with the lattice parameters a = 1620.4(3), b = 1657.6(3), c = 564.2(2) pm, V = 1.5154(5) nm3, R1 = 0.0375, wR2 = 0.0640 (all data). The crystal structure of Cu3B6O12 · H2O is built up from corner-sharing BO4 tetrahedra forming a three-dimensional network with channels along the c-axis. Inside these channels, the water molecules and a part of the copper ions are arranged.

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► High-pressure/high-temperature synthesis of the new borate hydrate Cu3B6O12 · H2O.
► Cu3B6O12 · H2O exhibits a structure similar to CuB2O4 (3 × CuB2O4 = Cu3B6O12).
► Analysis of the symmetry relations between CuB2O4 and Cu3B6O12 · H2O with a Bärnighausen tree.