Browsing by Subject "Ligands -- Synthesis."
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Item Chemistry of picolyl substituted phosphines.(2009-08-26T11:03:14Z) Low, Fernando Hung.; Klausmeyer, Kevin Kenneth, 1969-; Chemistry and Biochemistry.; Baylor University. Dept. of Chemistry and Biochemistry.The study and understanding of the coordination behavior of functional ligands with d¹⁰ "closed shell" metals has been active for many years, as it will continue to expand along with advances in characterization techniques such as X-ray crystallography. Interactions present in these metal complexes are typically associated with hydrogenbonding, π-π stacking effects, electrostatic and van der Waals interactions, of which none could be observed without an X-ray examination of the structure. As a result, design and synthesis of discrete and multi-dimensional coordinative structures have been made possible by understanding the binding behavior of the ligand and the different factors (anion, solvent, temperature, metal/ligand ratio) involved in the formation of the organic coordination architectures. In this work several multidentate pyridyl-phosphine ligands and their corresponding oxides have been used to construct a family of novel compounds, and bipyridine type molecules to synthesize mixed ligand complexes that vary from discrete molecules to polymeric arrays depending on the binding sites of the bipyridine. The luminescence, UV-visible, and electrochemical properties of these complexes were also studied, and seen to be dependent on the changes in structure and metal environment.Item Tridentate nitrogen ligands derived from 2,6-bis-hydrazinopyridine (BHP) : preparation and study of the 2,6-bis-hydrasonopyridines, 2, 6-bis-pyrazolylpytidines, and 2,6-bis-indazolylpyridines.(2009-06-02T17:55:17Z) Duncan, Nathan C.; Garner, Charles M. (Charles Manley), 1957-; Chemistry and Biochemistry.; Baylor University. Dept. of Chemistry and Biochemistry.The development of ligands for asymmetric catalysis has been a focal point in our research group. Tridentate nitrogen ligands have been used in a variety of asymmetric catalytic reactions. Of these, the 2,6-bis-pyrazolylpyridine class of ligands has found only limited use, due to difficulties in the normal synthetic route that limit the synthesis of ligands with bulky chiral groups attached to the pyrazole rings. The chiral derivatives that have been used in catalysis have shown modest to poor results, due in part to limitations in the synthesis of these ligands that prevent the development of bulky, chiral ligands. A new synthetic route has been developed using 2,6-bis-hydrazinopyridine (BHP). This route allows for a facile, one-pot synthesis of 2,6-bis-pyrazolylpyridines that is not limited by the bulkiness of the groups that become attached to the pyrazole ring. The primary focus of this research has been the development of new chiral 2,6-bis-pyrazolylpyridines and an investigation into the limitations of steric bulk on chelation ability in this class of ligands. For this purpose, several novel chiral ligands have been synthesized. The effect of sterics and electronics on the regioselectivity of the formation of the pyrazole ring was also studied in order to develop more regioselective routes to this class of ligands. The new bulky pyrazolylpyridine ligands that have been synthesized using this route have also been tested for the ability to sucessfully coordinate a transition metal. This study lead to a better understanding of the limitations the size of the substitutents attached to pyrazole ring have on the ligands’ ability to chelate metals. While BHP was developed primarily for the synthesis of the 2,6-bis-pyrazolylpyridine class of ligands, its use has now been expanded to the synthesis of other classes of tridentate-nitrogen ligands, many of which would be diffiuclt or impossible to synthesize through any other route. Using this new methodolgy, the syntheses of two novel classes of ligands, each with unique properties, the 2,6-bis-hydrazonopyridines and 2,6-bis-indazolylpyridines, have now been accomplished. The previously unknown 2,6-bis-indazolylpyridine class of ligands is offers the possibility to synthesize more robust catalysts than is possible using the bis-pyrazole ligands because of the electronic nature of the indazole ring.