The Assembly of Macrocyclic Bis- and Tetra-beta-lactams with Embedded Platinum or Palladium Square-Planar Centers

The synthesis, isolation, and full characterization of different types of stable, metal-assembled macrocyclic beta-lactams are reported. By using adequately functionalized bis-beta-lactams with defined stereochemistry as building blocks, a series of mono- and bimetallic Pd and Pt macrocycles has been prepared in good to quantitative yields. These novel structures combine the beta-lactam moiety with transition-metal fragments with cis-square-planar geometry and constitute a new class of metal-assembled cavities involving molecules with biological relevance as building blocks. By combining the adequate ligands, metallic fragments, and tuning the reaction conditions, different mono- and bimetallic macrocyclic beta-lactam cavities can be selectively obtained. Macrocycles with Pt-ethynyl groups are suitable to form host-silver triflate guest complexes in a tweezer fashion.