Crystal structure of a low-spin poly[di-μ3-cyanido-di-μ2-cyanido-bis­­(μ2-2-ethyl­pyrazine)­dicopper(I)iron(II)]

In the title metal–organic framework, [Fe(C6H8N2)2{Cu(CN)2}2]n, the low-spin FeII ion lies at an inversion centre and displays an elongated octa­hedral [FeN6] coordination environment. The axial positions are occupied by two symmetry-related bridging 2-ethyl­pyrazine ligands, while the equatorial positions are occupied by four N atoms of two pairs of symmetry-related cyanide groups. The CuI centre is coordinated by three cyanide carbon atoms and one N atom of a bridging 2-ethyl­pyrazine mol­ecule, which form a tetra­hedral coordination environment. Two neighbouring Cu atoms have a short Cu⋯Cu contact [2.4662 (7) Å] and their coordination tetra­hedra are connected through a common edge between two C atoms of cyanide groups. Each Cu2(CN)2 unit, formed by two neighbouring Cu atoms bridged by two carbons from a pair of μ-CN groups, is connected to six FeII centres via two bridging 2-ethyl­pyrazine mol­ecules and four cyanide groups, resulting in the formation of a polymeric three-dimensional metal–organic coordination framework.