Oxorhenium(V) complexes with a benzyldithiocarbazate ligand: synthesis, crystal structure, spectroscopic and DFT analyses

Abstract

Three new neutral oxorhenium(V) complexes were prepared with a 5-hydroxy-3-methyl-5-phenyl-pyrazoline-1-(S-benzyldithiocarbazate) ligand (H2bdtc): [ReOCl(bdtc)(PPh3)] (1), [ReOBr(bdtc)(PPh3)] (2) and [ReO(bdtc)(cysteamine)] (3). These rhenium complexes were characterized based on elemental, ESI(+)-MS, IR, NMR (1H and 31P), and X-ray diffraction analyses. The bdtc2- ligand took on different coordination arrangements in the rhenium complexes, including a planar equatorial coordination in 1 and a facial coordination in complex 3. Complexes 1 and 3 crystallize in monoclinic space groups P21/n and P21/c, respectively. The conformational stability caused by the unimolecular arrangement of the ligands was evaluated by the Density Functional Theory (DFT) calculation with the purpose of determining the balance involving the equilibrium among the possible stereoisomers in isolated phase and solvent. Moreover, frontier molecular orbitals, Natural Bond Orbital (NBO), Quantum Theory of Atoms in Molecules (QTAIM), bond order indices and molecular electrostatic potential analysis were performed to understand the electronic properties.