Fine-Tuning the Weak-Link Approach: Effect of Ligand Electron Density on the Formation of Rhodium(I) and Iridium(I) Metallomacrocycles

A novel bis(phosphinoalkyl-thioether)arene ligand with a fluorinated aryl group (1,4-(Ph(2)PCH(2)CH(2)S)(2)C(6)F(4)) has been synthesized. This ligand has been used to prepare symmetric bimetallic structures with Rh(I) and Ir(I) metal centers in high yield. Unlike their nonfluorinated counterparts, these complexes can be opened into large macrocyclic structures through straightforward ligand (i.e., carbon monoxide, nitriles, and isocyanides) substitution reactions at the metal-thioether linkage. In addition, the symmetric bimetallic structures have been shown to react with appropriately sized bifunctional aromatic molecules to form three-tiered host-guest structures.