sym-[5.5.5]Heterocyclophanes: structurally well-defined, mixed π/heteroatom-donor macrobicyclic cages

Abstract

Structural considerations for achieving conformational stability in cyclophanes are applied as design criteria in the synthesis of sym-[5.5.5]triaza- and sym-[5.5.5]trioxacyclophane macrobicycles. These compounds act as dynamic hosts in which the metal ion migrates between equivalent, C₃-related (η¹-C)₂N₂ coordination sites. The metal–arene interaction may alternatively be described as three centre, two-electron σ complexation to the C–H bond. Crystal structures of the copper(I) and silver(I) complexes show that little reorganization is required on the part of the ligand to accommodate the metal, and the former provides an unusual, structurally characterized example of eta-bonding of an arene to Cu^I.