On the Nature of Arene η6 Interactions in the Solid State and the Use of Cylindrophanes as Ligands for Sandwich Complexation of Metals with Longer-Range Interactions with the Benzene Ring

Abstract

A novel mode of containment for metal ions which participate in longer-range interactions with aryl rings (≥ 2.5 Å) is demonstrated in the preorganized cylindrical host 1. Three equatorial sulfur atoms in 1 hold metals in a trigonal planar ligand field between two apical benzene centroids at an M–Ar distance of about 3 Å. Evidence of an interaction between the π electrons and the metals is gained by 1H NMR spectroscopy of the complexes, and support for the general description of metal–arene contacts in the 2.5–3.5 Å range as ‘‘bonds’’ is derived from a statistical study of η6-coordination in the solid state. Crystal structures of [Ag(1)]BF4 and [Cu(1)]BF4 confirm the first examples of arene AgI and CuI sandwich complexation and indeed the only structurally characterized CuI-aryl centroid interaction. The two isomeric tris-sulfoxides derived from 1 show less tendency to interact with metals ions.