Synthesis, Raman, X-ray diffraction, and density functional studies of antimony(III) heterotetracycles displaying intramolecular transannular interactions O--- Sb.

A set of compounds of general formula [{S(C6H3S)2O}SbHal] [Hal = Cl (1), Br (2), I (3)] has been synthesized and studied by Raman and NMR spectroscopy as well as quantum chemical DFT calculations. X-ray diffraction studies of compound 2 revealed that the oxygen atom participates as donor and the antimony atom plays the role of acceptor, adopting a ?-distorted trigonal bi-pyramidal geometry, where the eight-membered central ring displays a boat?boat conformation. Furthermore, a series of DFT calculations was performed on compounds 1?3 as well as calculations on the non-synthesized heterotetracyclic systems [{S(C6H3S)2O}SbF] (4a) and the cation [{S(C6H3S)2O}Sb]+ (5a). The theoretic study at DFT level indicates as the electronegativity increases at exocyclic substituent along the set of compounds, the interaction is stronger. Moreover, the topological analysis of electronic density showed the existence of critical points along the O ? Sb direction which prompted us to suggest the existence of a dative bond.