Metallomacrocycles incorporating a hemilabile Tröger's base derived ligand

Tröger's base, a chiral molecule with a rigid 90° backbone, has been incorporated into a novel hemilabile phosphinoalkyl thioether ligand. Using the Weak Link Approach, this ligand has been reacted with Cu(CH ₃CN)₄PF₆ and [Rh(COE)₂Cl] _x (COE = cyclooctene) to form metallomacrocycles. Upon reaction of the ligand with Cu^I, which prefers a tetrahedral coordination geometry, a bimetallic macrocycle was formed. Alternatively, owing to the steric restrictions imposed by the 90° backbone of the ligand and the square-planar geometry of Rh^I, when the ligand was reacted with [Rh(COE)₂Cl]_x, the formation of bimetallic closed macrocycles was not observed, and instead a mixture of tri- and tetrametallic closed macrocycles is formed. Introducing pyridine to the Cu^I complex causes the weak thioether-Cu bonds to break, generating a large bimetallic open macrocycle. Upon reaction of the mixture of Rh^I metallomacrocycles with CO and Cl^-, the cyclic structure of these complexes becomes flexible enough that the dimeric bimetallic macrocycle forms, along with tri- and tetrameric open complexes. The mixture of differently sized Rh^I macrocyclic complexes has been analyzed using gel permeation chromatography, and the tetramer has been characterized by a single-crystal X-ray diffraction study. These are the first examples of metallomacrocycles containing a Tröger's base derivative.