Facile synthesis of a rare example of an iron(III) iodide complex, [FeI3(AsMe3)2], from the reaction of Me3AsI2 with unactivated iron powder

Abstract

The reaction of Me3AsI2 with unactivated iron powder provides a synthetic entry into the coordination chemistry of iron(III) iodide, which is inaccessible by traditional routes due to the low stability of the parent halide FeI3. The reaction of iron powder with Me3AsI2 results in the formation of a trigonal bipyramidal complex, [FeI3(AsMe3)2], which features the iodide ligands in the equatorial positions, and the Me3As groups occupying the axial positions. This complex is a rare example of an iron(III) iodide complex, and is the first iron(III) complex of a monodentate tertiary arsine ligand. The preparation of [FeI3(AsMe3)2] via the direct oxidation of iron powder further demonstrates that complexes of “soft” donor ligands can be prepared with “hard” transition metal centres, such as iron(III), in direct contravention of the HSAB principle. The structure of [FeI3(AsMe3)2] is isomorphous with all previously reported [MX3(EMe3)2] (M=main group or transition metal, X=halide, E=N, P, As) trigonal bipyramidal structures.