Organometallic Half-Sandwich Complexes: Rational Design, Synthesis And Applications

Supramolecular chemistry with organometallic half-sandwich complexes based on Ir, Rh, Ru fragments has received considerable attention over recent years. In this dissertation, some results in the rational design and synthesis of organometallic half-sandwich complexes and their potential applications are presented.(1) The binuclear complexes with two parallel coordination sites, such as oxalate (A), chloranilate (B), 1,4-dihydroxyanthraquinone (C) and 6,11-dihydroxy-5,12-naphthacenedione (D) bridging irdium, rhodium and ruthenium complexes can be served as precursors, which can be interlinked by pyridyl-based ligands.Following the general design strategy, many supramolecular rectangles, prisms and cages have been synthesized in high yields and characterized structurally. Efforts were paid to the functional properties and applications of these supramolecular structures, such as template-controlled topochemical photodimerization based on "organometallic macrocycles" through single-crystal-to-single-crystal transformation (SCSC), selectively recognize CH₂Cl₂ and ClCH₂CH₂Cl molecules with retention of single crystallinity in "organometallic molecular splints", and a simple, straightforward access to the preparation of metallo-prismatic cages able to encapsulate aromatic molecules was included. (2) The reactions of [Cp^*IrCl₂]₂ with a flexible pyridine-4-thiolate ligand are explored. We have synthesized mono-, tri- and tetra-iridium complexes containing pyridine-4-thiolato ligand and revealed their novel skeletal transformations from mono-iridium complex to tetra-iridium complex via using base. In addition, two new half-sandwich trinuclear complexes in which the bridging unit [L]^3- ([L]^3- = 1,3,5-triazine-2,4,6-trithiolato) functions as a tris-bidentate [N,S]^- donor ligand have been synthesized via the reactions of the bridging oxalato complexes with the trisodium salt of 1,3,5-triazine-2,4,6-trithiol, respectively. The reactions of half-sandwich iridium and rhodium complexes with 2-pyridinethione gave the corresponding mononuclear complexes also be studied.(3) By introducing additional nonlinear spacers between the two pyridine rings of bipyridine, such as the hindered rotation seen in the S-S bond of 4,4'-dipyridyldisulfide (4-DPDS) generates 2:2 M:L macrocyclic compounds. When the bidentate organochalcogen (S,Se) ligands bearing N-methylimidazole groups were used, we assembled several binuclear macrocycles rather than tetranuclear complexes.(4) Base on the rule of addition reaction at the metal center of [Cp^*Ir[E₂C₂(B₁₀H₁₀)] (E=S,Se), both of cluster-based carboranyl complexes and 2,6(7)-bis(4-pyridyl)-1,4,5,8-tetrathiafulvalene or Schiff-based bipyridyl ligands, have been proved to be versatile precursors to accomplish diverse architectures.(5) Aromatic C-H activation in a series of phenyl dimines was promoted by sodium acetate with [Cp^*MCl₂]₂ (M=Ir,Rh) at room temperature to form dicyclometalated compounds. The unsaturated molecule, dimethylacetylenedicarboxylate, was employed insert into the metal-carbon bonds of the cyclometalated compounds in order to expand the metallocycles. These compounds can be used as "clips", which can be interlinked by pyrazine to build supramolecular rectangles.