Magnetic Characteristics of Tetrabutylammonium Tetrahalogenoferrates(III): X-ray Crystal Structure of Tetrabutylammonium Tetrabromoferrate(III)

The crystal and molecular structure of tetrabutylammonium tetrabromoferrate(III) was determined. The iron cation is surrounded by four bromide anions, and it adopts a slightly distorted tetrahedral coordination with two angles larger than tetrahedral, one equal to tetrahedral and one smaller than tetrahedral. In the structure there are no hydrogen bonds nor any unusual short intermolecular interactions. The compound is isostructural with its [FeBr4−nCln]− (n = 0, 1, 3, 4) analogues. Magnetic measurements of the powdered samples of [(C4H9)4N][FeBr4−nCln] gave negative values of the Weiss constants that suggest antiferromagnetic interactions transmitted within the crystal lattice.