| This dissertation explores the design and synthesis of several new ligands of the general class 1,4-(Ph2PCH2CH 2X)2R {lcub}X = O, S, CH2, or O/S; R = C6H 4 or C6(CH3)4; Ph = phenyl{rcub} and their products with Rh(I) and Pd(II) metals. The “Weak-Link” approach to supramolecular complexes utilizes condensed intermediates that contain both strong and weak metal-ligand bonds to form target compounds. The weak bonds in these intermediates can be broken through straightforward ligand substitution reactions to yield larger open, bimetallic macrocycles in high yield. The research described here demonstrates how the electronic and steric properties, as well as charge, of the resulting macrocycles synthesized via this approach can be tailored through judicious choice of transition metal, hemilabile ligands, and ancillary ligands. Homobimetallic products result when symmetric ligands {lcub}X = S or O, R = C6H4 or C 6(CH3)4{rcub} that contain a weak bonding group, such as an ether or thioether, are reacted with Rh(I) or Pd(II). In the case of Rh(I), these dimeric products are kinetic products that can be converted, when heated, to monomeric products that are the thermodynamic products. An unsymmetric ligand {lcub}X = O/S, R = C6H4{rcub} that contains both ether and thioether moieties as weak bonding groups has been used to synthesize Rh(I) and Pd(II) heterobimetallic macrocycles. A phosphinoalkylarene ligand {lcub}X = CH2, R = C6H4{rcub} that does not contain the appropriate weakly bonding heteroatoms necessary for the “Weak-Link” reaction manifold has been synthesized, and its reactivity with Rh(I) has been explored. This ligand yields a mixture of monomeric, dimeric, and oligomeric products rather than a single dimeric product, which demonstrates the importance of the heteroatoms for the “Weak-Link” approach. Finally, the weak metal-ligand bonds of the dimeric products can be broken with neutral and anionic ligands to yield cationic, neutral, and anionic open macrocycles. The compounds have been characterized by 1H and 31P{lcub} 1H{rcub} NMR spectroscopies, combustion analysis, and mass spectrometry. Several complexes have been characterized by single crystal X-ray diffraction studies. |
