Light-driven N 2 cleavage into molecular nitrides is an attractive strategy for synthetic nitrogen fixation. However, suitable platforms are rare. Furthermore, the development of catalytic protocols via this elementary step suffers from poor understanding of N–N photosplitting within dinitrogen complexes, as well as of the thermochemical and kinetic framework for coupled follow-up chemistry. We here present a tungsten pincer platform, which undergoes fully reversible, thermal N 2 splitting and reverse nitride coupling, allowing for experimental derivation of thermodynamic and kinetic parameters of the N–N cleavage step. Selective N–N splitting was also obtained photolytically. DFT computations allocate the productive excitations within the {WNNW} core. Transient absorption spectroscopy shows ultrafast repopulation of the electronic ground state. Comparison with ground-state kinetics and resonance Raman data support a pathway for N–N photosplitting via a nonstatistically vibrationally excited ground state that benefits from vibronically coupled structural distortion of the core. Nitride carbonylation and release are demonstrated within a full synthetic cycle for trimethylsilylcyanate formation directly from N 2 and CO.

A novel operando spectroscopic approach combining multiwavelength and time-resolved Raman spectroscopy with gasphase Fourier transform infrared (FTIR) spectroscopy is presented, supported by in situ UV−vis diffuse reflectance (DR) spectroscopy. The potential of this approach is demonstrated in a case study of the oxidative dehydrogenation (ODH) of ethanol over a silica-supported vanadia catalyst. The structural dynamics of the catalyst upon switching from oxidative to reactive conditions was extensively studied by Raman spectroscopy with different excitation wavelengths in the visible and UV, exploiting resonance effects in a targeted manner. Time-dependent correlation of Raman and IR spectra over several reaction cycles allows identification of active vanadia surface structures. Detailed Raman spectroscopic analysis reveals that the adsorption of ethoxy species onto dispersed VO x structures occurs via opening of both V−O−Si and V−O−V bonds. During reaction, large oligomeric VO x structures are decomposed into smaller units. Combined Raman and UV−vis results show that these structural changes cannot be completely regenerated.

Nitride complexes are key species in homogeneous nitrogen fixation to NH 3 via stepwise protoncoupled electron transfer (PCET). In contrast, direct generation of nitrogenous organic products from N 2derived nitrides requires new strategies to enable efficient reductive nitride transfer in the presence of organic electrophiles. We here present a 2-step protocol for the conversion of dinitrogen to benzonitrile. Photoelectrochemical, reductive N 2 splitting produces a rhenium(V) nitride with unfavorable PCET thermochemistry towards ammonia generation. However, Nbenzoylation stabilizes subsequent reduction as a basis for selective nitrogen transfer in the presence of the organic electrophile and Brønsted acid at mild reduction potentials. This work offers a new strategy for photoelectrosynthetic nitrogen fixation beyond ammonia-to yield nitrogenous organic products.

An emerging approach for the activation of the nitrogen molecule is the light‐driven splitting of the N–N bond. Less than ten examples for complexes capable of N2 photoactivation are currently known, and the underlying photophysical and photochemical processes after light absorption are largely unresolved. All complexes have a central [M(µ‐η1:η1‐N2)M] unit with equivalent ligand spheres around each metal. For several of these complexes, small modifications of the ligand sphere result in thermal rather than photochemical activity. Herein, we analyse the electronic structures and computed UV/Vis spectra of four complexes: two thermally and two photochemically active complexes, each either involving molybdenum or tungsten. The analysis of electronic structures and spectra is based on the molecular orbitals, difference densities and the charge‐transfer numbers provided by TheoDORE. We find that the spectra of the photochemically active complexes contain excitations with more ligand‐to‐metal charge‐transfer character and higher intensity, providing a plausible explanation for light‐induced nitrogen splitting.

Nitride complexes are key species in homogeneous nitrogen fixation to NH 3 via stepwise protoncoupled electron transfer (PCET). In contrast, direct generation of nitrogenous organic products from N 2derived nitrides requires new strategies to enable efficient reductive nitride transfer in the presence of organic electrophiles. We here present a 2-step protocol for the conversion of dinitrogen to benzonitrile. Photoelectrochemical, reductive N 2 splitting produces a rhenium(V) nitride with unfavorable PCET thermochemistry towards ammonia generation. However, Nbenzoylation stabilizes subsequent reduction as a basis for selective nitrogen transfer in the presence of the organic electrophile and Brønsted acid at mild reduction potentials. This work offers a new strategy for photoelectrosynthetic nitrogen fixation beyond ammonia-to yield nitrogenous organic products.