Cyanate Formation via Photolytic Splitting of Dinitrogen

Light-driven N2 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
N2 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 N2 and CO.