K3FeSe3 und K3Fe2Se4, zwei neue Verbindungen im System K/Fe/Se

K₃FeSe₃ and K₃Fe₂Se₄, Two New Compounds in the System K/Fe/Se The two selenides K₃FeSe₃ and K₃Fe₂Se₄ were synthesised by fusion reactions of potassium carbonate with iron and selenium in a stream of hydrogen charged with selenium at 695 °C and 710–730 °C, respectively. The crystal structures were determined by single‐crystal X‐ray diffractometer data. The atomic arrangement of K₃FeSe₃ is characterised by edge sharing Fe₂Se₆] double tetrahedra separated by potassium ions (space group P2₁/c, Z = 4). The characteristic structural unit of the mixed‐valent compound K₃Fe₂Se₄ is a zig‐zag chain of edge‐sharing, iron‐centred selenium tetrahedra, again separated by potassium ions (space group Pnma, Z = 4).