K 4 Ni 3 O 6 and KNa 2 Ni 2 O 4 , New Quasi One‐Dimensional Oxonickelates(II, III)

Two new quasi one‐dimensional alkali metal oxonickelates, K 4 Ni 3 O 6 and KNa 2 Ni 2 O 4 , were obtained by the azide/nitrate route starting from respective stoichiometric mixtures of KN 3 , KNO 3 , NaN 3 , NaNO 3 , and NiO. According to the X‐ray analyses of the crystal structures [K 4 Ni 3 O 6 : C 2/ m , Z = 2, a = 899, 53(3), b = 610, 24(2), c = 778.75(2) pm, β = 91.665(2)°, R 1 = 0.030, w R 2 = 0.088; KNa 2 Ni 2 O 4 : P 2 1 / n , Z = 4, a = 573.70(2), b = 1072.89(3), c = 844.93(2) pm, β = 102.916(2)°, R 1 = 0.038, w R 2 = 0.108], the main feature common to both crystal structures are undulating 1 ∞ NiO 2 chains consisting of planar, edge‐sharing NiO 4 squares. The magnetic susceptibilities for both compounds indicate onset of antiferromagnetic ordering at about 5 K. Evaluations of the Curie‐Weiss fits result in calculated magnetic moments higher than expected for the respective spin only values, implying some orbital contribution. Below the Néel temperature spin flop or meta‐magnetism is observed for both compounds.