A large, X-shaped polyoxometalate [As6Fe7Mo22O98]25− assembled from [AsMo7O27]9− and [FeMo4O19]11− moieties

Abstract

A large X-shaped polyoxometalate, [As₆Fe₇Mo₂₂O₉₈]²⁵⁻ (1), has been synthesized and structurally characterized. The skeleton of 1 is composed of two monocapped hexavacant Keggin [AsMo₇O₂₇]⁹⁻ units and two divacant Anderson [FeMo₄O₁₉]¹¹⁻ units fused together through a central Fe₅O₄ core and two μ₄-As₂O bridging units, resulting in a unique tetramer with C_2h symmetry. The polyanion represents the largest iron-containing arsenomolybdate to date and it contains an unprecedented heptanuclear iron(III) cluster. The investigation of the magnetic properties shows that the Fe₇ cluster exhibits an overall ferromagnetic interaction with a spin ground state of S = 7.5.