Alkali-metal trifluoromonosulphatomanganates (III) A<SUB>2</SUB>[MnF<SUB>3</SUB>(SO<SUB>4</SUB>)] (A = NH<SUB>4</SUB>, Li, Na or K)

Pink-brown crystalline alkali-metal trifluoromonosulphatomanganates(III), A2[MnF3(SO4)] (A = NH4, Li, Na or K), have been synthesised in high yields by reacting KMnO4 or MnO(OH) with 40% HF and A2SO4 or by the reaction of MnO(OH) with 40% HF and A2S2O8 (A = NH4 or K). The chemicallly estimated oxidation state of manganese occurs between 2.9 and 3.1, and the room temperature magnetic moments lie in the range 4.0-4.2 BM. (NH4)2[MnF3(SO4)] on being pyrolysed at 340&#176;C yields MnSO4