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(CH3CN)4PF6
and [Rh(COE)2Cl]x (COE = cyclooctene) to form metallomacrocycles. Upon reaction of the ligand with CuI, 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 RhI, 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 CuI complex causes the
weak thioether−Cu bonds to break, generating a large bimetallic open macrocycle. Upon reaction of the mixture
of RhI 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 RhI 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.