Photoinduced Metallonitrene Formation by N<sub>2</sub> Elimination from Azide Diradical Ligands
Luis I. Domenianni, Markus Bauer, Till Schmidt‐Räntsch, Jörg Lindner, Sven Schneider, Peter Vöhringer
Abstract
Abstract Transition‐metal nitrides/nitrenes are highly promising reagents for catalytic nitrogen‐atom‐transfer reactivity. They are typically prepared in situ upon optically induced N 2 elimination from azido precursors. A full exploitation of their catalytic potential, however, requires in‐depth knowledge of the primary photo‐induced processes and the structural/electronic factors mediating the N 2 loss with birth of the terminal metal‐nitrogen core. Using femtosecond infrared spectroscopy, we elucidate here the primary molecular‐level mechanisms responsible for the formation of a unique platinum(II) nitrene with a triplet ground state from a closed‐shell platinum(II) azide precursor. The spectroscopic data in combination with quantum‐chemical calculations provide compelling evidence that product formation requires the initial occupation of a singlet excited state with an anionic azide diradical ligand that is bound to a low‐spin d 8 ‐configured Pt II ion. Subsequent intersystem crossing generates the Pt‐bound triplet azide diradical, which smoothly evolves into the triplet nitrene via N 2 loss in a near barrierless adiabatic dissociation. Our data highlight the importance of the productive, N 2 ‐releasing state possessing azide ππ* character as a design principle for accessing efficient N‐atom‐transfer catalysts.