Novel zwitterionic oxorhenium(V) complexes:: Synthesis, characterization and crystal structure of [ReOX2(Hdhp)(PPh3)] (X = Cl, Br; H2dhp=2,3-dihydroxypyridine)

Two novel zwitterionic oxorhenium(V) complexes, [ReOCl2(Hdhp)(PPh3)] (1) and [ReOBr2(Hdhp)(PPh3)] (2) (H-2 dhp = 2,3-dihydroxypyridine), were synthesized and characterized by infrared spectroscopy, H-1 and P-31 nuclear magnetic resonance, elemental analysis and crystal and molecular structure determination by X-ray diffraction on single crystals. Both complexes show distorted octahedral coordination geometry, with the halide ligands arranged in equatorial cis positions, the triphenylphosphine ligand in a trans position to one of the halides and the Hdhp(-) ligand coordinated in a bidentate form through its oxygen atoms, one in trans position to the oxo-ligand and the other in trans position to the second halide. The nitrogen atom of this ligand is protonated. Compounds 1 and 2 show quite different crystal packing, both influenced by hydrogen bonds of the types N-H center dot center dot center dot X (X = Cl, Br) and N-H center dot center dot center dot O.