Synthesis, structure and magnetic properties of copper(II) complexes of 2-amino-5-trifluoromethylpyridine (5-TFMAP): (5-TFMAP)2CuX2 (X = Cl or Br), (5-TFMAP)3CuBr2 and [(5-TFMAP)2CuBr2](5-TFMAPH)Br

Abstract

Reaction of 2-amino-5-trifluoromethylpyridine (5-TFMAP) with copper halides in water or alcohol solvents produced four coordination complexes: (5-TFMAP)2CuX2, (X=Cl (1) or Br (2)), (5-TFMAP)3CuBr2 (3) and [(5-TFMAP)2CuBr2](5-TFMAPH)Br (4). In all compounds, the 5-TFMAP ligands are coordinated to the Cu(II) ion through the pyridine nitrogen atom in a trans-geometry and a nearly square planar environment is observed in 1, 2 and 4. In 3, coordination of an additional 5-TFMAP ligand results in a distorted trigonal bipyramidal complex. All complexes are characterized by single-crystal X-ray diffraction. Compound 1 crystalizes as a chain structure via pairs of long Cl…Cu contacts between molecules and the temperature dependent magnetic susceptibility data has been fit to an alternating chain model, resulting in J=−5.97(1)K and J′=−0.95(4)K. Compound 2 exhibits weaker antiferromagnetic interactions, also via the bihalide superexchange pathway, resulting in J=−3.02(2)K from a fit to the uniform chain model. The structure of compound 3 also exhibits a uniform antiferromagnetic chain, but via the two-halide pathway (short Br…Br contacts) and susceptibility data exhibit significantly stronger interactions (J=−31.05(5)K). Compound 4 is not stable in air and loses a molecule of 5-TFMAP from the crystal lattice upon standing.