Crystal structure of poly[bis(l-2-bromopyrazine)- tetra-l2-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 octahedral coordination environment [FeN6], ligated by two pyrazine N atoms of symmetry-related bridging 2-bromopyrazine molecules 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-bromopyrazine molecule. Copper(I) centers related by a twofold rotation axis are bridged by two carbon atoms from a pair of -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 -CN groups and two bridging 2-bromopyrazine ligands, resulting in the formation of a metal–organic framework, which is additionally stabilized by the short Cu Cu contacts of 2.4450 (7) A˚.