Microwave-assisted Synthesis of Pentamethylcyclopentadienyl Iridium Dihalide Dimers

• Published in: Polyhedron 2022-11, Vol.226, p.116089, Article 116089
• Main Authors: Chang, Elizabeth T., Green, David B., Brereton, Kelsey R.
• Format: Article
• Language: English
• Subjects: electrochemistry; iridium; microwave-assisted synthesis; spectroscopy
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2022.116089

Microwave-assisted synthetic (MAS) preparation of cyclopentadienyl iridium halide dimers. Complexes can be access directly through the iridium halide salts and pentamethylcyclopentadiene as well as through halide metathesis from the iridium chloride dimer and a potassium halide salt. All complexes can be accessed using MAS in less than fifteen minutes without loss of yield or purity. [Display omitted] [Cp*IrCl2]2 is a common precursor used to synthesize a large family of organometallic catalysts. While [Cp*IrCl2]2 is commercially available, dimers featuring other halides are not, although they can be accessed through [Cp*IrCl2]2. Published synthetic methods for the preparation of these halide dimers are time consuming, requiring reflux for 48 hours. We have developed a new synthetic approach utilizing microwave-assisted synthesis (MAS) that significantly decreases the time required to prepare [Cp*IrX2]2 (X = Cl, Br, I). Reagents were heated beyond their normal boiling point in sealed reactors for 15 min at 120°C and products were isolated using traditional methods with yields comparable or exceeding literature methods. [Cp*IrX2]2 dimers synthesized using MAS were characterized by NMR spectroscopy, UV-Visible spectroscopy, and elemental analysis. These dimers were then used to synthesize a series of mononuclear iridium bipyridyl complexes, [Cp*Ir(bpy)X]X. This series of complexes was explored spectroscopically and electrochemically to identify potential electrocatalysts for future studies.