Crystal structure of BaMnB2O5 containing structurally isolated manganese oxide sheets

In an attempt to search for mixed alkaline-earth and transition metal pyroborates, the title compound, barium manganese(II) pyroborate, has been synthesized by employing a flux method. The structure of BaMnB2O5 is composed of MnO5 square pyramids that form Mn2O8 dimers by edge-sharing and of pyroborate units ([B2O5]4-) that are composed of two corner-sharing trigonal-planar BO3 units. These building blocks share corners to form ∞2[MnB2O5]2- layers extending parallel to (100). The Ba2+ cations reside in the gap between two manganese pyroborate slabs with a coordination number of nine. The title compound forms an inter-esting spiral framework propagating along the 21 screw axis. The structure is characterized by two alternating layers, which is relatively rare among known transition-metal-based pyroborate compounds.