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.
Bibliographical noteFunding Information:
The authors acknowledge financial support by the German-Israeli Foundation for Scientific Research and Development (GIF, Research Agreement Project I-1369-302.5/2016). A fellowship for H.L.V. from the Ministry of Science and Technology is gratefully acknowledged. The authors thank Dr. L. J. W. Shimon for assistance with the X-ray structure of 8.
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