Synthesis and magnetic characteristics of new tetrachloroferrates(III) with 2-methylpyridinium, 3-methylpyridinium and 4-methylpyridinium cations: X-ray crystal structure of 4-methylpyridinium tetrachloroferrate(III)

The crystal and molecular structure of a new 4-methylpyridinium tetrachloroferrate(III) of molecular formula [4-Me(Py)H][FeCl4] was determined. The iron cation is four coordinated by chlorine anions, and it adopts a slightly distorted tetrahedral coordination. with two angles smaller, three equal and one larger than tetrahedral one. The compound is isostructural with its 2- and 3-methylpyridinium analogues. Magnetic measurements of the powdered samples gave negative values of the Weiss constants equal -7.3 K, -6.6 K and -6.2 K for [2-Me(Py)H][FeCl4], [3-Me(Py)H][FeCl4] and [4-Me(Py)H][FeCl4], respectively, which suggest antiferromagnetic coupling. The susceptibility curves of all complexes exhibit maxima indicating the presence of antiferromagnetic ordering with a Neel temperature of approximately 7 K. (C) 2007 Elsevier B.V. All rights reserved.