Nitrenium-Based Iridium Complexes: Stabilization of a Dihydrogen σ-Complex

N-heterocyclic carbenes are well known and commonly used as ligands in organometallic chemistry. However, the analogue ligands based on isoelectronic nitrogen cation has only recently been disclosed by our group. A new type of cationic nitrenium-based PNP pincer ligands, bearing two phosphine arms, successfully coordinate to neutral, cationic and dicationic late transition metal centers (Scheme).^[[i]]

Scheme. Pincer type nitrenium ligands coordinate to a variety of late transition metals in different oxidation states.

We extend our studies to the catalytically important Ir species.

Here we present the mono- and di-cationic Ir(III) complexes coordinated to the N-heterocyclic nitrenium. The formation of the nitrenium-metal bond is confirmed in solution, by selective ¹⁵N-labelling experiments, and/or in the solid state, by X-ray crystallography.

Utilizing our system, we were able to isolate an Ir-dihydrogen σ-complex at room temperature and ambient pressure. This species undergoes oxidative addition to yield a well-define Ir(III)-dihydride. A comparison to the analog Rh(I) complex is also presented.^[[ii]]

[[i]] (a) Tulchinsky, Y.; Iron, M. A.; Botoshansky, M.; Gandelman, M. Nature Chem. 2011, 3, 525-531. (b) Tulchinsky, Y.; Kozuch, S.; Saha, P.; Botoshansky, M.; Shimon, L.; Gandelman, M. Chem. Sci. 2014, 5, 1305-1311. (c) Tulchinsky, Y.; Kozuch, S.; Saha, P.; Mauda, A.; Nisnevich, G.; Botoshansky, M.; Shimon, L. J. W.; Gandelman, M. Chem. Eur. J. 2015, 21, 7099−7110.

[[ii]] Unpublished results.