Proton-hydride tautomerism in hydrogen evolution catalysis.

Area of Science:

• Catalysis
• Renewable Energy
• Hydrogen Production

Background:

• Efficient hydrogen generation is crucial for renewable energy.
• Understanding catalytic intermediates is key to optimizing H2 production.
• Few intermediates in 2e(-) + 2H(+) → H2 catalysis have been observed.

Purpose of the Study:

• To isolate and characterize a key intermediate in 2e(-) + 2H(+) → H2 catalysis.
• To elucidate the mechanism of hydrogen production using Cp*Rh(bpy) complex.
• To explore facile and reversible interconversion of H(+) and H2.

Main Methods:

• Treatment of Cp*Rh(bpy) (Cp*, η(5)-pentamethylcyclopentadienyl; bpy, κ(2)-2,2'-bipyridyl) with acid.
• Chemical characterization of the resulting intermediate.
• Protonation studies to observe H2 evolution.

Main Results:

• Isolation and characterization of a novel catalytic intermediate.
• The intermediate was identified as a species with [η(4)-Cp*H] as a ligand, not a hydride.
• Delivery of a second proton led to H2 evolution and reformation of η(5)-Cp* bound to rhodium(III).

Conclusions:

• The Cp*Rh(bpy) complex catalyzes facile and reversible interconversion of H(+) and H2.
• The identified intermediate is crucial for understanding the catalytic cycle.
• This work provides insights for developing more efficient catalysts for hydrogen production.