Flux growth and structure of two compounds with the EuIn 2 P 2 structure type, A In 2 P 2 ( A = Ca and Sr), and a new structure type, BaIn 2 P 2

Single crystals of the new Zintl phases A In 2 P 2 [ A = Ca (calcium indium phosphide), Sr (strontium indium phosphide) and Ba (barium indium phosphide)] have been synthesized from a reactive indium flux. CaIn 2 P 2 and SrIn 2 P 2 are isostructural with EuIn 2 P 2 and crystallize in the space group P 6 3 / mmc . The alkaline earth cations A are located at a site with m symmetry; In and P are located at sites with 3 m symmetry. The structure type consists of layers of A 2+ cations separated by [In 2 P 2 ] 2− anions that contain [In 2 P 6 ] eclipsed ethane‐like units that are further connected by shared P atoms. This yields a double layer of six‐membered rings in which the In—In bonds are parallel to the c axis and to one another. BaIn 2 P 2 crystallizes in a new structure type in the space group P 2 1 / m with Z = 4, with all atoms residing on sites of mirror symmetry. The structure contains layers of Ba 2+ cations separated by [In 2 P 2 ] 2− layers of staggered [In 2 P 6 ] units that form a mixture of four‐, five‐ and six‐membered rings. As a consequence of this more complicated layered structure, both the steric and electronic requirements of the large Ba 2+ cation are met.