Synthesis, properties and crystal structures of benzene-1,2-dithiolato complexes of antimony-(III) and -(V)

Abstract

Anaerobic treatment of SbCl₃ with 1,2-(LiS)₂C₆H₄ provided a reliable route to [Sb(1,2-S₂C₆H₄)₂]^– which in turn produced [Sb(1,2-S₂C₆H₄)₃]^– on reaction with 1,2-(HS)₂C₆H₄ and O₂ in very good yields ([NEt₄]⁺ salt, ca. 82%). Tetraalkylammonium salts of [Sb(1,2-S₂C₆H₄)₂]^– were isolated after metathesis with either [NEt₄]Br ([NEt₄]⁺ salt, ca. 72%) or [NBuⁿ₄]l ([NBuⁿ₄]⁺ salt, ca. 90%). Slowly cooling hot MeCN solutions of [Net₄][Sb(1,2-S₂C₆H₄)₂] gave yellow single crystals. This compound is the first structurally characterized anionic thiolate complex of Sb^III. In its structure the stereochemical influence of the lone pair of electrons leads to a distorted Ψ-trigonal-bipyramidal environment [S_ax–Sb–S_ax 158.95(3), S_eq–Sb–S_eq 105.08(3)°], however, the degree of distortion is less severe than expected for a complex with a normalized bite (b) of 1.31. Dark purple single crystals of [NEt₄][Sb(1,2-S₂C₆H₄)₃] were obtained by slowly cooling hot MeCN–MeOH solutions. The co-ordination geometry about Sb is slightly distorted from octahedral with a twist angle of 49.22(3)° and most structural parameters are within 10% of octahedral values.