Dinitrogen dissociation on an isolated surface tantalum atom

Area of Science:

• Heterogeneous catalysis
• Inorganic chemistry
• Materials science

Background:

• Industrial and biochemical ammonia synthesis typically require multi-metallic cooperation for dinitrogen (N2) bond cleavage.
• This principle of multimetallic cooperation extends to molecular systems and surfaces for dinitrogen reductive cleavage.

Purpose of the Study:

• To investigate the possibility of dinitrogen cleavage using isolated, single-site metal complexes.
• To explore a novel catalytic system for nitrogen fixation under mild conditions.

Main Methods:

• Synthesis of silica surface-supported tantalum(III) and tantalum(V) hydride centers.
• Reaction of these centers with dihydrogen (H2) at 250°C and atmospheric pressure.
• Characterization using infrared (IR) spectroscopy, solid-state nuclear magnetic resonance (NMR) spectroscopy, isotopic labeling, X-ray absorption spectroscopy, and theoretical simulations.
• In situ IR spectroscopy for monitoring reaction intermediates.

Main Results:

• Observed cleavage of dinitrogen at 250°C and atmospheric pressure by dihydrogen on isolated tantalum hydride sites.
• Formation of a tantalum(V) amido imido product, [(identical with SiO)2Ta(=NH)(NH2)].
• Identification of reaction intermediates suggesting a mechanism distinct from known N2 activation systems.

Conclusions:

• Single-site tantalum hydride complexes on silica can cleave dinitrogen under relatively mild conditions.
• The observed mechanism for N2 cleavage is novel and differs significantly from established pathways in enzymatic, organometallic, and heterogeneous systems.
• This finding opens new avenues for developing catalysts for ammonia synthesis and nitrogen fixation.