Two-dimensional coordination compounds based on Fe(II) and Co(III) hexacyanometallates with Cu(II)(dien) groups: Structures and magnetic properties

The crystal structures of two copper(II)(dien) coordination compounds with diamagnetic [Fe(II)(CN)6]4− or [Co(III)(CN)6]3− bridges were determined from single crystal X-ray diffraction and their magnetic properties investigated by SQUID measurements. The first, {[Cu(dien)]2[Fe(CN)6]}n·4n H2O (1), where dien is diethylenetriamine, consists of linear Cu(II)–Fe(II)–Cu(II) trimers. The Cu2+ ions are equatorially coordinated by dien and bridged by a hexacyanoferrate anion. A two-dimensional network is formed through longer axial Cu⋯NC–Fe bonds. The second, {{[(Cu(dien))2(pz)]2[Co(CN)6]}[Co(CN)6]}n·6n H2O (2), where pz− is pyrazolate, contains butterfly-shaped Cu(II)2–Co(III)–Cu(II)2 pentamers. The Cu2+ ions are again equatorially coordinated by dien and bridged by pz− to form a dimer. Two dimers are linked through a [Co(III)(CN)6]3− anion to pentanuclear clusters, which are further connected into a layer via the second site of [Co(III)(CN)6]3− anions. Cu2+ has distorted square–pyramidal and octahedral coordination for 1 and 2, respectively, with elongated axial ligand distances due to the Jahn–Teller effect. The magnetic behavior of both compounds is consistent with Cu2+ S = ½ dimers, although with different bridging groups to give g = 2.157(2) and 2J/kB = −1.14(1) K for 1 and g = 2.15(1) and 2J/kB = −37.5(2) K for 2.