Rubidium‐Pentafluoromanganat(III) und dessen Monohydrat, strukturelle Daten und Topotaxiebeziehungen

Rubidiumpentafluoromanganate (III) and its monohydrate, crystal data and topotaxy The unit cells and most probable space groups of the new compounds Rb 2 MnF 5 · H 2 O and Rb 2 MnF 5 have been determined from single crystal X‐ray diffraction data and the powder diffraction patterns indexed.\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Rb}_{\rm 2} {\rm MnF}_{\rm 5} {\rm } \cdot {\rm H}_{\rm 2} {\rm O: orthorhombic, } \,a = {\rm 9}{\rm .407(2) } {\AA}, b = 8.202(2){\AA}, c = 8.344(2) {\AA}, {\rm D}_{2{\rm h}}^{17} - {\rm Cmcm;} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Rb}_{\rm 2} {\rm MnF}_{\rm 5} {\rm : tetragonal, }\,a = {\rm 6}{\rm .103(1) }{\AA},\, c = 4.140(1) {\AA}, {\rm C}_{4{\rm h}}^1 - {\rm P4/m \,or }{\rm D}_{4{\rm h}}^1 - {\rm P4/mmm}{\rm} $$\end{document} . By analogy to the stoichiometrically similar phases high temperature K 2 MnF 5 · H 2 O, the unit cell of which has also been determined and its powder diffraction pattern indexed, and (NH 4 ) 2 MnF 5 , model structures for the rubidium salts are proposed. Both structures consist of infinite chains of corner sharing coordination octahedra [MnF 6 ], between which the rubidium ions and in the case of the hydrate additional water molecules are located. X‐ray diffraction and scanning electron microscopical investigations of the dehydration of the hydrate clearly point to a chain controlled topotactic reaction mechnism. This supports the proposed model structures and confirms the possibility of predicting topotactic reaction mechanisms.