Synthesis and Characteristics of Iridium Complexes Bearing N-Heterocyclic Nitrenium Cationic Ligands

Abstract

N-Heterocyclic nitrenium cations are isostructural and isoelectronic analogues of the ubiquitous N-heterocyclic carbene. We present the first examples of coordination of nitrenium ions to the Ir­(I) and Ir­(III) metal centers. This work includes rare complexes with cation–cation interactions between a positively charged ligand and an iridium ion. These species represent the first example of iridium complexes bearing any cationic ligand of group 15 elements analogous to the Arduengo carbene. These nitrenium-based monocationic and even dicationic Ir­(I) complexes can smoothly oxidatively activate H2 at room temperature and ambient pressure. Utilizing our system, we were able to observe an Ir–dihydrogen σ-complex, which undergoes oxidative addition to yield a well-defined Ir­(III) dihydride. Comparative studies of the analogous Rh­(I)–nitrenium species, which exhibit reversible dihydrogen activation, are presented. New Ir complexes were fully characterized by multinuclear nuclear magnetic resonance (including 15N labeling) and X-ray crystallography.

N-Heterocyclic Nitreniums Can Be Employed as Photoredox Catalysts for the Single-Electron Reduction of Aryl Halides

“…Their further application has been recently demonstrated in photo/NHC dual catalysis . However, being the isoelectronic and isostructural analogues of NHCs, the development of N-heterocyclic nitrenium (NHN) chemistry is still in its infancy . NHNs exhibit amphoteric behavior due to the copresence of a lone pair and a vacant p π orbital.…”

PSb+P Ligand: Platform for a Stibenium to Transition-Metal Interaction

“…In recent years, the PCP pincer ligands of benzannulated NHC and its isovalent p-block analogues have proven to be effective in achieving robust transition-metal catalysts. − The central coordinating sites of the PEP moiety ranging from group 13 boryl to group 14 tetrylene and to group 15 nitrenium , have been explored. To seek a molecular platform that allows the study of the stibenium–metal interaction, we have prepared the corresponding pincer-chlorostibine ligand P­(Sb-Cl)P ( 1 ) from the reaction of SbCl 3 and 1,2-bis­(diphenylphosphinomethylamino)­benzene (Scheme ).…”

Bidentate Triazolate-Based Ligand System: Synthesis, Coordination Modes, and Cooperative Bond Activation

“…Metal complexes based on such ligands have been employed in various structural, stoichiometric, and catalytic studies. , Most ligands in these studies bear a neutral triazole framework. We have recently introduced a positively charged derivative, triazolium cation, as a ligand for transition metals . While some examples of anionic triazolate ligands are known, all of them, to the best of our knowledge, have been exclusively used for the structural studies of metal complexes. , We envisioned that such triazolate ligands (namely, a corresponding triazolate/triazole couple), substituted with an additional anchor ligand, can represent an attractive system for cooperative metal–ligand (M–L) bond activation and catalysis (Scheme ).…”