Homo- und heteronukleare Bindungen bei schweren Elementen der 15. und 16. Gruppe

Abstract

Binuclear molecules R 2 E-ER 2 or R-Y-Y-R, formed by the heavier pnicogen (E) or chalkogen atoms (Y), respectively, tend to align in homonuclear linear chains in the solid state, if steric requirements introduced by the substituents R do not prevent this association. Going from the third period elements phosphorus or sulfur to their higher homologues, the longer intermolecular distances within these chains gradually change in nature from normal van der Waals contacts to secondary bonds. For distibanes and dibismuthanes the differing bonding situations between the solid and liquid states are reflected in a bathochromic colour shift upon crystallization. Mononuclear halogenostibanes and -bismuthanes with aromatic groups are subject to intermolecular association, too, if there are enough electronegative substituents to invoke a sufficient Lewis acidity at the pnicogen atom. Non-classical pnicogen-arene interactions are found together with asymmetrie halogeno bridges for aryl-substituted stibanes. Only one of the corresponding bismuthanes has been investigated up to now; it shows symmetrie halogeno bridges, but no bismuth-arene coordination.