Synthesis, characterizations and crystal structures of antimony(III) complexes with nitrogen-containing ligands

Six antimony adducts with N-donor neutral ligands (1,10-phenanthroline, 4,4′-bipyridine) have been obtained following the reaction of antimony halides with phenanthroline and 4,4′-bipyridine. By changing the solvent and stoichiometry, we obtained six different complexes, Sb(phen)Cl3 (1), Sb(phen)Br3 (2), Sb2(phen)4Br8 (3) and Sb(bpy)Cl3 (4), Sb(bpy)2Cl3 (5), Sb(bpyH · bpyH2)Br6 (6) (where phen = 1,10-phenanthroline, bpy = 4,4′-bipyridine). All the complexes have been characterized via elemental analysis, FT-IR and NMR (1H, 13C) spectroscopy. The crystal structures of complexes 2, 3 and 6 have been determined by X-ray single crystal diffraction. The structural analysis show that the coordination sphere around antimony atom in complex 2 is a distorted square pyramid, coordinated by three bromine atoms and two nitrogen atoms from phen. In complex 3, the central antimony atom is six-coordinated through four bromine atoms and two nitrogen atoms forming a distorted octahedral geometry. Besides that, there are also uncoordinated 1,10-phenanthroline bonded by hydrogen bonds and π–π stacking interactions, which is rarely observed in previous reports. The crystal structure of complex 6 consists of bpyH · bpyH2 trications and hexabromoantimonate trianions. The antimony atom in the anion has a distorted octahedral environment. Additionally, all complexes present a 3D framework built up by N–H⋯Br, C–H⋯Br and C–H⋯Cl weak hydrogen bonds interactions.