Copper(II) halide complexes of aminopyridines: Syntheses, structures and magnetic properties of [(5CAP)2CuX2] and [(5BAP)nCuX2] (X = Cl, Br)

Abstract

Reaction of 2-amino-5-halopyridine molecules with Cu(II) halides in the solid state via mechanochemical techniques produced four coordination complexes, (5BAP)2CuBr2 (2a), (5BAP)2CuCl2 (3), (5CAP)2CuCl2 (4), (5CAP)2CuBr2 (5) [5BAP = 2-amino-5-bromopyridine; 5CAP = 2-amino-5-chloropyridine]. In all compounds, the 5BAP or 5CAP ligands are coordinated to the Cu(II) ion through the pyridine N atom along with two halide ions. Compounds 2 and 3 crystallized in the P-1 and P21/c space groups, respectively. Temperature dependent magnetic susceptibility data for 2 were fit to the antiferromagnetic rectangle model (J = –4.5(2) K; α = 0.89(17)), while the data for 3 were fit to the uniform chain model (J = –4.20(6) K), indicating a significant difference in the interchain interactions. Both 4 and 5 crystallize with the 5CAP ligands in the syn-conformation in the space groups I2/a and P21/n, respectively. Compound 4 formed the expected dimeric structure via bridging chloride ions and the magnetic data were successfully fit to the dimer model (J = –2.57(5) K), while 5 unexpectedly formed a structural chain via Br…Br contacts which exhibits very weak antiferromagnetic interactions. An intermediate structure, (5BAP)(H2O)CuBr2 (1), was prepared and characterized via mechanochemical methods along with an isomer of (5BAP)2CuBr2 (2b).