Jahn‐Teller‐Ordnung in pipzH 2 [Mn 2 F 8 ], einem Fluoromanganat(III) mit neuer Schichtstruktur

Jahn‐Teller Ordering in pipzH 2 [Mn 2 F 8 ], a Fluoromanganate(III) with a New Layer Structure From a solution of (pipzH 2 )[MnF 2 (HPO 4 )(H 2 O)]·(H 2 PO 4 ) in concentrated hydrofluoric acid the title compound could be crystallized and was characterized by X‐ray crystallography: monoclinic, space group P 2 1 / n , Z = 8, a = 13.275(1), 10.400(1), c = 14.928(1) Å, β = 112.337(8), R = 0.0265. The structure shows a new type of anionic layers [Mn 2 F 8 ] built of dimers of edge‐sharing [MnF 6 ] octahedra linked via common vertices, alternating with layers of piperazinium(2+) cations. A dense network of hydrogen bonds N–H···F achieves a strong 3D interconnection. Strong elongation of the [MnF 6 ] octahedra is observed due to the Jahn‐Teller effect.The long axes show parallel (ferrodistortive) orientation within the dimers, but the ordering between the dimers is antiferrodistorive. A possible mechanism of formation is discussed on the basis of precursor structures.