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

In the title metal-organic framework, [Fe(C₆H₈N₂)₂{Cu(CN)₂}₂] , the low-spin Fe^II ion lies at an inversion centre and displays an elongated octa-hedral [FeN₆] coordination environment. The axial positions are occupied by two symmetry-related bridging 2-ethyl-pyrazine ligands, while the equatorial positions are occupied by four N atoms of two pairs of symmetry-related cyanide groups. The Cu^I centre is coordinated by three cyanide carbon atoms and one N atom of a bridging 2-ethyl-pyrazine mol-ecule, which form a tetra-hedral coordination environment. Two neighbouring Cu atoms have a short Cu⋯Cu contact [2.4662 (7) Å] and their coordination tetra-hedra 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 Fe^II centres via two bridging 2-ethyl-pyrazine mol-ecules and four cyanide groups, resulting in the formation of a polymeric three-dimensional metal-organic coordination framework.