Structures and magnetic behaviour of hydroxo-bridged CrIII aggregates: [Cr4(μ-OH)4(hpdta)2]2− and [Cr6(μ-OH)8(hpdta)2(en)2]

The syntheses and crystal structures of the tetra- and hexanuclear CrIII aggregates (enH2)[Cr4(μ-OH)4(hpdta)2]·512H2O(1a), [Ba(OH2)5{Cr4(μ-OH)4(hpdta)2}] · 13H2O (1b) [Cr6(μ-OH)8(hpdta)2(en)2] · 10H2O (2a) and [Cr6(μ-OH)8(hpdta)2(en)2] · 14H2O (2b) (H5hpdta = 2-hydroxypropane-1,3-diaminetetraacetic acid) are reported and discussed. The antiferromagnetic interactions mediated by the bridging hydroxo ligands have been quantified. The fact that there are only a few such examples in the literature with similar bridges leads to the conclusion that a meaningful magnetostructural correlation, such as that recently proposed for oxo- and hydroxo-bridged FeIII aggregates, is not yet possible in the case of CrIII.

Hydroxo-bridged Cr(III) tetranuclear and hexanuclear aggregates show antiferromagnetic coupling which can be modelled relatively easily. The parallels to the structures and properties of the related Fe(III) and Al(III) compounds are discussed.Figure optionsDownload as PowerPoint slide