Silver-Free Synthesis of Iridium-Aqua Complexes by Heterogeneous Solid-Phase Ion-Exchange
Presentation Type
Poster
Presentation Type
Submission
Keywords
photocatalyst, electrocatalyst, solid-phase ion exchange, iridium halide, iridium-aqua
Department
Chemistry
Major
Chemistry
Abstract
Pentamethylcyclopentadienyl iridium-aqua complexes are utilized as catalysts for a variety of transformations in aqueous and organic solvents. Traditional methods to access the aqua complexes from their chloride precursors rely on solubility-driven chloride removal by silver salts, where an excess of the silver salt is typically required for complete conversion from the iridium chloride complex to the iridium-aqua complex. This residual, redox active, silver frequently interferes in electrochemical experiments. To avoid this interference, we developed a new solid-phase synthetic approach to synthesize the iridium-aqua complexes directly from the iridium halide precursor, completely bypassing the use of silver. This new pathway is less expensive than the use of silver salts and does not compromise yields of, or conversions to, the iridium-aqua complexes. We have optimized and expanded the versatility of this method by substantially reducing the volume of the conversion reagent needed. Our method results in successful conversion of the halide ligand (bromide or iodide) to aqua with only slight variations in procedure. Density Functional Theory calculations are used to compare theoretical Ir-X bond strengths across the series and used to justify the varied synthesis parameters. Product characterization by 1 H NMR spectroscopy, UV-Visible spectroscopy, and cyclic voltammetry confirms successful conversion of the iridium halide to the desired iridium-aqua complex and the absence of any adventitious silver.
Faculty Mentor
Kelsey Brereton
Funding Source or Research Program
Summer Undergraduate Research Program
Location
Waves Cafeteria
Start Date
24-3-2023 2:00 PM
End Date
24-3-2023 4:00 PM
Silver-Free Synthesis of Iridium-Aqua Complexes by Heterogeneous Solid-Phase Ion-Exchange
Waves Cafeteria
Pentamethylcyclopentadienyl iridium-aqua complexes are utilized as catalysts for a variety of transformations in aqueous and organic solvents. Traditional methods to access the aqua complexes from their chloride precursors rely on solubility-driven chloride removal by silver salts, where an excess of the silver salt is typically required for complete conversion from the iridium chloride complex to the iridium-aqua complex. This residual, redox active, silver frequently interferes in electrochemical experiments. To avoid this interference, we developed a new solid-phase synthetic approach to synthesize the iridium-aqua complexes directly from the iridium halide precursor, completely bypassing the use of silver. This new pathway is less expensive than the use of silver salts and does not compromise yields of, or conversions to, the iridium-aqua complexes. We have optimized and expanded the versatility of this method by substantially reducing the volume of the conversion reagent needed. Our method results in successful conversion of the halide ligand (bromide or iodide) to aqua with only slight variations in procedure. Density Functional Theory calculations are used to compare theoretical Ir-X bond strengths across the series and used to justify the varied synthesis parameters. Product characterization by 1 H NMR spectroscopy, UV-Visible spectroscopy, and cyclic voltammetry confirms successful conversion of the iridium halide to the desired iridium-aqua complex and the absence of any adventitious silver.