Synthesis and magnetic characteristic of new tetrabromo- and tetrachloroferrates(III) with 2-methylquinolinium cation: X-ray crystal structure of bis(2-methylquinolinium) bromide tetrabromoferrate(III)

The crystal and molecular structure of a new 2-methylquinolinium [2-Me(QH)] salt of stoichiometry (2-Me(QH))2FeBr5 was determined. The iron cation is four coordinated by bromine anions, and it adopts a slightly distorted tetrahedral coordination with two angles smaller than tetrahedral, two equal to tetrahedral and two larger than tetrahedral. In the structure two intermolecular N–H⋯Br hydrogen bonds link the 2-MeQH+ cations to dimers via a Br− bridge. The compound is isostructural with its chloride analog, (2-Me(QH))2FeCl5. Magnetic measurements of the powdered samples gave negative values of Weiss constants equal −3.1 K for (2-Me(QH))2FeCl5 and −10.2 K for (2-Me(QH))2FeBr5 that suggest antiferromagnetic coupling. The susceptibility curves for (2-Me(QH))2FeBr5 exhibit a maximum at 6 K indicating the presence of antiferromagnetic interactions transmitted in the crystal lattice.