Crystal structure of cyanometallates Me ₃ [ Co ( CN ) ₆ ] ₂ and KMe [ Fe ( CN ) ₆ ] with Me = Mn ²⁺ , Ni ²⁺ , Cu ²⁺

The crystal structure of four cyanometallates has been determined from X-ray powder diffraction data using the Rietveld method. The variously hydrated compounds Cu 3 [ Co ( CN ) 6 ] 2 , Mn 3 [ Co ( CN ) 6 ] 2 and KNi [ Fe ( CN ) 6 ] crystallize at cubic symmetry ( Fm 3 m ) with lattice parameters 10.032(2), 10.413(3) and 10.234(5) Å, respectively. The crystal of KMn [ Fe ( CN ) 6 ]·2 H 2 O shows a monoclinic structure ( P 2 1 / c ) with the lattice parameters a =10.108(2) Å, b =10.104(3) Å, c =10.114(3) Å, β=92°, 93°. The starting model was based on an isomorphic Mn 3 [ Co ( CN ) 6 ] 2 single crystal structure, where Co and Mn ions are octahedrally coordinated by C and N atoms, respectively, forming three-dimensional bimetallic networks with the C ≡ N groups as bridging ligands.