Hybrid materials containing organometallic cations and 3-D anionic metal dicyanamide networks of type [Cp*2M][M′(dca)3]

Abstract

A new series of hybrid materials of type [Cp*₂M][M′(dca)₃] has been prepared by cation templation and structurally characterised (M = Fe(III), Co(III); M′ = Mn(II), Fe(II), Co(II), Ni(II), Cd(II); dca⁻ = N(CN)₂⁻). The crystallographic analysis of [Cp*₂Fe][Cd(dca)₃] showed that the [Cd(dca)₃]⁻ anionic framework is of a symmetrical 3-D α-polonium type, containing octahedral Cd nodes and μ_1,5-dca bridging ligands. The [Cp*₂Fe]⁺ cations occupy the cube-like cavities within the framework. The cationic and anionic-framework sublattices remain magnetically independent and display susceptibilities, over the range 300 to 2 K, of a Curie–Weiss nature obtained by adding a S = 1/2 (Cp*₂Fe⁺) or a S = 0 (Cp*₂Co⁺) contribution to those of the weakly antiferromagnetically coupled frameworks of M′. These hybrid species do not show any intrinsic long-range magnetic order. The present [Cp*₂Fe][M′(dca)₃] series display the characteristic, unusually shaped [Cp*₂Fe]⁺ Mössbauer line, in the range 295–5 K, assigned (below 101 K) as the sum of a narrow and a broad line. Relaxation effects were evident. The [Fe(dca)₃]⁻ compound showed superimposed low-spin Fe(III) and high-spin Fe(II) lines, the latter giving relaxation broadening effects.