Das erste Oxoferrat(I): Zur Konstitution von K3[FeO2] und K3[NiO2]

The First Oxoferrate(I): On the Constitution of K₃[FeO₂] and K₃[NiO₂] Garnet-red single crystals of K₃[FeO₂] were obtained for the first time by heating intimate mixtures of K₆[CdO₄] and CdO (molar ratio 1:1.16) in closed Fe-cylinders at 450°C during 40 d. The same way of preparation via “reaction with the cylinder surface” was applied to prepare similarly coloured single crystals of K₃[NiO₂] (K₆CdO₄ in closed Ni-cylinders at 500°C during 49 d). The structure determination by four circle diffractometer data (MoKα , K₃[FeO₂]: 731 out of 731 I_o(hkl), R = 5.76%, R_w = 5.33%, K₃[NiO₂]: 755 out of 755 I_o(hkl), R = 8.70%, R_w = 4.25%) confirms the space groups P 4₁2₁2 and P 4₃2₁2, respectively. K₃[FeO₂]: a = 604.2(2) pm, c = 1 402.7(3) pm, Z = 4 K₃[NiO₂]: a = 603.6(1) pm, c = 1 405.2(2) pm, Z = 4. (powder data, standard deviations in parentheses) Essential feature of the structure are the dumb-bell-like anions [O? M? O]^3? (M = Fe, Ni). Their arrangement corresponds to a stuffed derivative of the KrF₂-type. Magnetic properties of K₃[FeO₂] were determined and cover the monovalence of Fe. MAPLE-calculations reveal the strong coincidence of monovalent VIIIb-cations.