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

Abstract

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 ·4 n H 2O ( 1), where dien is diethylenetriamine, consists of linear Cu(II)–Fe(II)–Cu(II) trimers. The Cu 2+ 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 ·6 n H 2O ( 2), where pz − is pyrazolate, contains butterfly-shaped Cu(II) 2–Co(III)–Cu(II) 2 pentamers. The Cu 2+ 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. Cu 2+ 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 Cu 2+ S = ½ dimers, although with different bridging groups to give g = 2.157(2) and 2 J/ k B = −1.14(1) K for 1 and g = 2.15(1) and 2 J/ k B = −37.5(2) K for 2.