Unusual molecular complexes of antimony fluoride dimers with acetonitrile and pyridine: structures and bonding

The structures of two new molecular complexes of antimony pentafluoride with pyridine (Py) and acetonitrile (AN), SbF₅·Py and Sb₂F₁₀·AN, and a molecular complex of antimony trifluoride Sb₂F₆·Py and its ionic derivative [HPy]⁺[Sb₂F₇]^- in the solid state have been determined by single crystal X-ray structural analysis. The complexes Sb₂F₁₀·AN and Sb₂F₆·Py are the first structurally characterized compounds of dimeric antimony fluorides. To reveal the nature of bonding in the complexes and their stability, DFT computations of the electronic structure and thermodynamic characteristics were performed, in particular the analysis of the electrostatic potentials, the orbital interactions and the topology. The results indicate that the intermolecular Sb⋯F interactions can be described as a network of pnictogen bonds.

Nmr study of the solution structures of TcO(2)F(3) and ReO(2)F(3)

Both TcO(2)F(3) and ReO(2)F(3) are infinite chain, fluorine-bridged polymers in the solid state. Their solution structures have been studied by (19)F and (99)Tc NMR spectroscopy in SO(2)ClF solution and shown to exhibit cyclic (MO(2)F(3))(3) (M = Tc, Re) and (ReO(2)F(3))(4) structures that have been confirmed by simulation of the (19)F NMR spectra. The trimers dominate in both the technetium and rhenium systems, with both the tetramer and trimer existing in equilibrium in the rhenium system. A low concentration of a higher, possibly pentameric, cyclic rhenium polymorph is also present in equilibrium with the trimer and tetramer.