Cyano‐Bridged Aqua(N,N‐Dimethylacetamide)(cyanoiron)lanthanides from Samarium,Gadolinium, or Holmium Nitrate and Potassium Hexacyanoferrate: Crystal Structures and Magnetochemistry

Three cyano‐bridged aqua(N,N‐dimethylacetamide)(cyanoiron)lanthanide complexes were synthesized by the reaction of K₃Fe(CN)₆, Ln(NO₃)₃?6 H₂O (Ln=Sm, Gd, Ho), and N,N‐dimethylacetamide (DMA). The obtained complexes 1 – 3 exhibit different coordination geometries and crystal structures. The polymeric {Sm(DMA)₂(H₂O)₄Fe(CN)₆?5 H₂O}_n (SmFe]_n; 1 ) has a one‐dimensional chain structure with approximately parallel trans‐positioned bridging CN ligands between the Sm‐ and Fe‐atoms. (Gd(DMA)₃(H₂O)₄)₂Fe(CN)₆]?Fe(CN)₆]?3 H₂O (Gd₂Fe; 2 ) is an isolated trinuclear Gd(1)?Fe?Gd(2) complex with two approximately perpendicular cis‐positioned bridging CN ligands between the two Gd‐atoms and the Fe‐atom. Ho(DMA)₃(H₂O)₃Fe(CN)₆]?3 H₂O (HoFe; 3 ) adopts a single dinuclear crystal structure with only one bridging CN between the Ho‐ and Fe‐atom. Magnetochemistry experiments establish weak antiferromagnetic interactions between Gd^III (and Ho^III) and Fe^III atoms. Especially the SmFe]_n complex 1 exhibits long‐range magnetic ordering, T_c=3.5 K, and a stronger coercive force, H_c=1400 Oe.