π‐Complexes of p‐Block Elements: Planar Dihydroanthracene in a Menshutkin Complex. Crystal Structure of Br₃Sb · C₆H₄(CH₂)₂C₆H₄ · SbBr₃

Crystals of a 1:2 complex of 9,10‐dihydroanthracene and antimony tribromide are obtained from toluene solutions of the components. In the crystal the complex forms corrugated sheets of an inorganic (SbBr 3 ) n coordination polymer, which are cross‐linked by antimony coordination to the benzene rings of the dihydroanthracene molecules are also arranged in folded layers. The dihydroanthracene molecules reside on centers of inversion and their carbon skeleton is planar within the limits of the experiment. With contacts from opposite sides of the molecular plane, the dihydroanthracene is η 6 ,(η 6 )'‐coordinated to the Sb(III) centers at distances of 3.25 Å. In a very irregular geometry the coordination sphere of the crystallographically equivalent antimony atoms contains bromine neighbours at different distances. – Antimony trichloride and dihydroanthracene form a complex of ambiguous stoichiometry, while bismuth trichloride again gives a 2;1 complex, the structure of which has not yet been determined.