| This dissertation describes the synthesis, characterization, and reactivity of mono- and binuclear macrocycles and two-legged piano-stool monomers constructed from symmetric and dissymmetric hemilabile ligands via the weak-link approach. The symmetric thioether ligand, 1,4-bis[2-(diphenylphosphino)ethylthio]benzene, was synthesized and reacts with Rh(I), Pd(II), and Ir(I) to form a series of condensed intermediate macrocycles. The substitutionally robust Rh(I) and Pd(II) structures can be opened in the presence of a halide source and CO or KCN to form 26-membered neutral macrocycles via the weak-link approach. The generality of these reactions is demonstrated by the formation of analogous ether based neutral macrocycles from their condensed intermediate structures. This synthetic strategy allows one to easily tailor the properties of transition metals and macrocycle cavities.; Studies aimed at stabilizing mononuclear two-legged piano stool Rh(II) complexes resulted in the synthesis of ligands 1,4-bis[4-(diphenylphosphino)butyl]-2,3,5,6-tetramethylbenzene, 1,4-bis[2-(diphenylphosphino)pro-poxy]-2,3,5,6-tetramethylbenzene, and 1,4-bis[2-(diphenylphosphino)ethoxy]-2,3,5,6-tetramethylbenzene. Electrochemical studies determined that symmetric chelation, electron rich arene rings, and phosphine moieties that are connected through a four unit spacer group increase the stability of Rh(II) complexes in a two-legged piano-stool geometry. The stabilizing effects of the symmetrically substituted arene rings, when coordinated to the rhodium metal centers, led to the isolation of the first two mononuclear Rh(II) complexes in a two-legged piano-stool geometry. In fact, the Rh(II) monomer, [(η6-1,4-bis[4-(diphenylphosphino)butyl]-2,3,5,6-tetramethylbenzene)Rh][PF 6]2, was structurally characterized by single-crystal X-ray diffraction methods, making it one of only 15 structurally characterized Rh(II) monomers.; Finally, chiral condensed intermediate structures have been synthesized via the weak-link approach using hemilabile ligands that incorporate C 2 symmetric chiral auxiliaries. The weak links in these structures can be broken in the presence of σ-donating and π-accepting small molecules like CO, nitriles, and isonitriles. The resulting chiral macrocycles have potential as chiral molecular recognition agents. |
