Anomalous Stoichiometry and Antiferromagnetic Ordering for the Extended Hydroxymanganese(II) Cubes/Hexacyanometalate‐Based 3D‐Structured [MnII4(OH)4][MnII(CN)6](OH2)6⋅H2O

The reaction of MnII(O2CMe)2 and NaCN or LiCN in water forms a light green insoluble material. Structural solution and Rietveld refinement of high‐resolution synchrotron powder diffraction data for this unprecedented, complicated compound of previously unknown composition revealed a new alkali‐free ordered structural motif with [MnII4(μ3‐OH)4]4+ cubes and octahedral [MnII(CN)6]4− ions interconnected in 3D by MnII‐N≡C‐MnII linkages. The composition is {[MnII(OH2)3][MnII(OH2)]3}(μ3‐OH)4][MnII(μ‐CN)2(CN)4]⋅H2O=[MnII4(μ3‐OH)4(OH2)6][MnII(μ‐CN)2(CN)4]⋅H2O, which is further simplified to [Mn4(OH)4][Mn(CN)6](OH2)7 (1). 1 has four high‐spin (S=5/2) MnII sites that are antiferromagnetically coupled within the cube and are antiferromagnetically coupled to six low‐spin (S=1/2) octahedral [MnII(CN)6]4− ions. Above 40 K the magnetic susceptibility, χ(T), can be fitted to the Curie–Weiss expression, χ ∝(T−θ)−1, with θ=−13.4 K, indicative of significant antiferromagnetic coupling and 1 orders as an antiferromagnet at Tc=7.8 K. Structural solution and Rietveld refinement of high‐resolution diffraction data for an unprecedented, complicated compound of previously unknown composition revealed a new alkali‐free ordered structural motif with [MnII4(μ3‐OH)4]4+ cubes and octahedral [MnII(CN)6]4− ions interconnected in 3D. [ABSTRACT FROM AUTHOR]