Transition metal
complexes with a doubly deprotonated diazomethane
(CNN2–) ligand have been proposed as fleeting intermediates
in nitrogen transfer reactions. However, in contrast to isoelectronic
azide (N3
–), well-defined examples are
unknown. We here report the synthesis and characterization of isolable
complexes with terminal and bridging CNN2– ligands,
stabilized by platinum(II) pincer fragments. Bonding within the allenic
dimetallanitrilimine core (Pt–NNC–Pt)
was probed by oxidation of the bridging ligand. Enhanced reactivity
toward [3 + 2]-cycloaddition with CO2 was obtained. Photofragmentation
favors N–NC over NN–C bond cleavage as a route to cyanide
and a transient metallonitrene complex.
We report a detailed computational and experimental study
of the
fixation and reductive coupling of dinitrogen with low-valent boron
compounds. Consistent with our mechanistic findings, the selectivity
toward nitrogen fixation or coupling can be controlled through either
steric bulk or the reaction conditions, allowing for the on-demand
synthesis of nitrogen chains. The electronic structure and intriguing
magnetic properties of intermediates and products of the reaction
of dinitrogen with borylenes are also elucidated using high-level
computational approaches.
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