Yb3CoSn6 and Yb4Mn2Sn5: New polar intermetallics with 3D open-framework structures

Two new ternary ytterbium transition metal stannides, namely, Yb3CoSn6 and Yb4Mn2Sn5, have been obtained by solid-state reactions of the corresponding pure elements in welded tantalum tubes at high temperature. Their crystal structures have been established by single-crystal X-ray diffraction studies. Yb3CoSn6 crystallizes in the orthorhombic space group Cmcm (no. 63) with cell parameters of a=4.662(2), b=15.964(6), c=13.140(5) Å, V=978.0(6) Å3, and Z=4. Its structure features a three-dimensional (3D) open-framework composed of unusual [CoSn3] layers interconnected by zigzag Sn chains, forming large tunnels along the c-axis which are occupied by the ytterbium cations. Yb4Mn2Sn5 is monoclinic space group C2/m (no. 12) with cell parameters of a=16.937(2), b=4.5949(3), c=7.6489(7) Å, β=106.176(4)°, V=571.70(8) Å3, and Z=2. It belongs to the Mg5Si6 structure type and its anionic substructure is composed of parallel [Mn2Sn2] ladders interconnected by unusual zigzag [Sn3] chains, forming large tunnels along the c-axis, which are filled by the ytterbium cations. Band structure calculations based on density function theory methods were also made for both compounds.