Crystal structure of poly[bis-(μ-2-bromo-pyrazine)-tetra-μ2-cyanido-dicopper(I)iron(II)]: a bimetallic metal-organic framework.

Abstract

In the title metal-organic framework, [Fe(C4H3BrN2)2{Cu(CN)2}2] n , the FeII cation is located on an inversion center and has a slightly elongated octa-hedral coordination environment [FeN6], ligated by two pyrazine N atoms of symmetry-related bridging 2-bromo-pyrazine mol-ecules in the axial positions and by four N atoms of pairs of symmetry-related cyanido groups in the equatorial positions. The CuI center has a fourfold coordination environment [CuC3N], with an almost perfect trigonal-pyramidal geometry, formed by three cyanido C atoms and an N atom of a bridging 2-bromo-pyrazine mol-ecule. Copper(I) centers related by a twofold rotation axis are bridged by two carbon atoms from a pair of μ-CN groups, resulting in Cu2(CN)2 units. Each Cu2(CN)2 unit is linked to six FeII cations via a pair of linear CN units, the pair of μ-CN groups and two bridging 2-bromo-pyrazine ligands, resulting in the formation of a metal-organic framework, which is additionally stabilized by the short Cu⋯Cu contacts of 2.4450 (7) Å.