Metallomacrocycles incorporating a hemilabile Tröger's base derived ligand

Tröger's base, a chiral molecule with a rigid 90 degrees backbone, has been incorporated into a novel hemilabile phosphinoalkyl thioether ligand. Using the Weak Link Approach, this ligand has been reacted with Cu(CH3CN)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 degrees 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.