Menshutkin Complexes: Influence of Pnictogen, Halide, and Arene on Pn···π_arene Interactions in [(PnX₃)₂{(2-R-C₆H₄)C₂H₄(2-R-C₆H₄)}]

More than 100 years ago, B. N. Menshutkin systematically studied phase diagrams of antimony(III) halides with aromatic hydrocarbons for the first time, leading to the discovery of what is known today as Menshutkin complexes. As an extension to the wide variety of these Pn···π_arene type complexes, which have been nicely reviewed by Schmidbaur and Schier in 2008, a series of isomorphous compounds with diphenylethane derivatives as organic linkers in supramolecular networks are reported. By setting up a library of complexes consisting of PnX₃ (Pn = Sb, Bi; X = Cl, Br) and (2-R-C₆H₄)C₂H₄(2-R-C₆H₄) (R = Me, Br, NH₂, NO₂), the structures of five new Menshutkin complexes and six additionally isolated Sb···R donor–acceptor type complexes are compared. Lewis basic R-groups favor the formation of donor–acceptor complexes whereas weaker ones lead to Pn···π_arene complexes. The influence of the pnictogen atom (Pn), the halide (X), and the substituent (R) concerning Pn···π_arene distances in the solid state of the isomorphous Menshutkin complexes is examined. The results are discussed in view of previous studies providing a deeper insight into the qualitative and quantitative nature of Pn···π_arene interactions.