A Cp* iridium complex containing a tricyclic, dianionic, tridentate, scorpionate (facial binding), mixed organic-inorganic ligand was synthesized and characterized by single-crystal X-ray crystallography, as well as polynuclear NMR, UV-vis, and IR spectroscopies. The central cycle of the tridentate ligand consists of a modified boroxine in which two of the boron centers are tetrahedral, anionic borates. The complex is stable to hydrolysis in aqueous solution for &gt;9 weeks at 25 °C but reacts with a 50 mM solution of sodium periodate within 12 seconds to form a periodate- driven oxygen evolution catalyst that has a turnover frequency of in excess of 15 per second. The active catalyst species is short-lived, achieving an average turnover number of ca. 2500 molecules of oxygen per atom of iridium, before reaching near-complete deactivation within 300 seconds. Nanoparticles were not observed on this time scale but did form within 4 h of catalyst activation under these experimental conditions. The parent complex was modeled using density functional theory, which accurately reflected the geometry of the complex and indicated significant interaction of iridium- and boracycle-centered orbitals.

Synthesis of an organometallic iridium complex containing a dianionic, tridentate, mixed organic−inorganic ligand: A fast-acting and short-lived oxygen evolving catalyst

254th National Meeting (2017)

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