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Transition‐metal nitrides/nitrenes are highly promising reagents for catalytic nitrogen‐atom‐transfer reactivity. They are typically prepared in situ upon optically induced N2 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 N2 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 d8‐configured PtII ion. Subsequent intersystem crossing generates the Pt‐bound triplet azide diradical, which smoothly evolves into the triplet nitrene via N2 loss in a near barrierless adiabatic dissociation. Our data highlight the importance of the productive, N2‐releasing state possessing azide ππ* character as a design principle for accessing efficient N‐atom‐transfer catalysts. [ABSTRACT FROM AUTHOR]

The reaction of TaMe3Cl2 with the rigid acridane‐derived trisamine H3NNN yields the tantalum(V) complex [TaCl2(NNNcat)]. Subsequent reaction with dioxygen results in the full four‐electron reduction of O2 yielding the oxido‐bridged bimetallic complex [{TaCl2(NNNsq)}2O]. This dinuclear complex features an open‐shell ground state due to partial ligand oxidation and was comprehensively characterized by single crystal X‐ray diffraction, LIFDI mass spectrometry, NMR, EPR, IR and UV/VIS/NIR spectroscopy. The mechanism of O2 activation was investigated by DFT calculations revealing initial binding of O2 to the tantalum(V) center followed by complete O2 scission to produce a terminal oxido‐complex. [ABSTRACT FROM AUTHOR]

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., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The reaction of TaMe 3 Cl 2 with the rigid acridane-derived trisamine H 3 NNN yields the tantalum(V) complex [TaCl 2 (NNN cat )]. Subsequent reaction with dioxygen results in the full four-electron reduction of O 2 yielding the oxido-bridged bimetallic complex [{TaCl 2 (NNN sq )} 2 O]. This dinuclear complex features an open-shell ground state due to partial ligand oxidation and was comprehensively characterized by single crystal X-ray diffraction, LIFDI mass spectrometry, NMR, EPR, IR and UV/VIS/NIR spectroscopy. The mechanism of O 2 activation was investigated by DFT calculations revealing initial binding of O 2 to the tantalum(V) center followed by complete O 2 scission to produce a terminal oxido-complex., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

C-H amination and amidation by catalytic nitrene transfer are well-established and typically proceed via electrophilic attack of nitrenoid intermediates. In contrast, the insertion of (formal) terminal nitride ligands into C-H bonds is much less developed and catalytic nitrogen atom transfer remains unknown. We here report the synthesis of a formal terminal nitride complex of palladium. Photocrystallographic, magnetic, and computational characterization support the assignment as an authentic metallonitrene (Pd-N) with a diradical nitrogen ligand that is singly bonded to Pd II . Despite the subvalent nitrene character, selective C-H insertion with aldehydes follows nucleophilic selectivity. Transamidation of the benzamide product is enabled by reaction with N 3 SiMe 3 . Based on these results, a photocatalytic protocol for aldehyde C-H trimethylsilylamidation was developed that exhibits inverted, nucleophilic selectivity as compared to typical nitrene transfer catalysis. This first example of catalytic C-H nitrogen atom transfer offers facile access to primary amides after deprotection., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)