A coordinatively unsaturated iridium complex with an unsymmetrical redox-active ligand: (spectro)electrochemical and reactivity studies

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 48; no. 37; pp. 13931 - 13942
• Main Authors: Sobottka, Sebastian, van der Meer, Margarethe Behr, Glais, Estelle, Albold, Uta, Suhr, Simon, Su, Cheng-Yong, Sarkar, Biprajit
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 24.09.2019
• Subjects: Activation; Coordination compounds; Crystallography; Infrared spectroscopy; Iridium compounds; Ligands; Methylation; NMR; Nuclear magnetic resonance; Phenylenediamine; Spectra; Substrates
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c9dt01597c

Redox-active ligands, owing to their electron reservoir capability, are well suited for the generation of coordinatively unsaturated metal complexes. We present here iridium complexes with an unsymmetrically substituted o -phenylenediamine ligand. A coordinatively unsaturated, formally iridium( iii ) complex with the fully reduced o -phenylenediamide (or o -diamidobenzene) ligand was isolated and structurally characterized. This coordinatively unsaturated metal complex undergoes methylation reactions with a CH 3 + source to form a new species with an Ir-CH 3 bond. The redox-active Ir-CH 3 complex performs the activation of CDCl 3 . The same activation reaction was also tested for other haloforms. In all types of reactions, the masked coordination site at the metal center and the electron reservoir behavior of the redox-active ligand are used for reactivity. Furthermore, we show that the aforementioned iridium( iii ) complex performs redox-induced dihydrogen activation. This activation process was used to catalytically transfer the electrons and protons of dihydrogen to a substrate molecule. Crystallographic, spectroscopic, electrochemical, spectroelectrochemical and DFT methods were used to elucidate the geometric and the electronic structures of the metal complex in the various redox forms and to probe the mechanism of the investigated reactions. We demonstrate here how the cooperative behavior between a catalytically active metal center and a redox non-innocent ligand can be utilized to perform substrate bond activation and transformation. Metal-ligand cooperativity can be used in iridium complexes with an unsymmetrically substituted redox-active diamidobenzene ligand for bond activation reactions.