Crystal structures of tetra­methyl­ammonium (2,2′-bi­pyridine)­tetra­cyanidoferrate(III) trihydrate and poly[(2,2′-bi­pyridine-κ2N,N′)di-μ2-cyanido-dicyanido(μ-ethyl­enedi­amine)(ethyl­enedi­amine-κ2N,N′)­cadmium(II)iron(II)] monohydrate]

The crystal structures of the building block tetra­methyl­ammonium (2,2′-bi­pyridine-κ2N,N′)tetra­cyanidoferrate(III) trihydrate, [N(CH3)4][Fe(CN)4(C10H8N2)]·3H2O, (I), and a new two-dimensional cyanide-bridged bimetallic coordination polymer, poly[(2,2′-bi­pyridine-κ2N,N′)di-μ2-cyanido-dicyanido(μ-ethyl­enedi­amine-κ2N:N′)(ethyl­enedi­amine-κ2N,N′)cadmium(II)iron(II)] monohydrate], [CdFe(CN)4(C10H8N2)(C2H8N2)2]·H2O, (II), are reported. In the crystal of (I), pairs of [Fe(2,2′-bipy)(CN)4]− units (2,2′-bipy is 2,2′-bi­pyri­dine) are linked together through π–π stacking between the pyridyl rings of the 2,2′-bipy ligands to form a graphite-like structure parallel to the ab plane. The three independent water mol­ecules are hydrogen-bonded alternately with each other, forming a ladder chain structure with R44(8) and R66(12) graph-set ring motifs, while the disordered [N(CH3)4]+ cations lie above and below the water chains, and the packing is stabilized by weak C—H⋯O hydrogen bonds. The water chains are further linked with adjacent sheets into a three-dimensional network via O—H⋯O hydrogen bonds involving the lattice water mol­ecules and the N atoms of terminal cyanide groups of the [Fe(2,2′-bipy)(CN)4]− building blocks, forming an R44(12) ring motif. Compound (II) features a two-dimensional {[Fe(2,2′-bipy)(CN)4Cd(en)2]}n layer structure (en is ethyl­enedi­amine) extending parallel to (010) and constructed from {[Fe(2,2′-bipy)(CN)4Cd(en)]}n chains inter­linked by bridging en ligands at the Cd atoms. Classical O—H⋯N and N—H⋯O hydrogen bonds involving the lattice water mol­ecule and N atoms of terminal cyanide groups and the N—H groups of the en ligands are observed within the layers. The layers are further connected via π–π stacking inter­actions between adjacent pyridine rings of the 2,2′-bipy ligands, completing a three-dimensional supra­molecular structure.