Proton-hydride tautomerism in hydrogen evolution catalysis

Proc Natl Acad Sci U S A. 2016 Jun 7;113(23):6409-14. doi: 10.1073/pnas.1606018113. Epub 2016 May 24.

Abstract

Efficient generation of hydrogen from renewable resources requires development of catalysts that avoid deep wells and high barriers. Information about the energy landscape for H2 production can be obtained by chemical characterization of catalytic intermediates, but few have been observed to date. We have isolated and characterized a key intermediate in 2e(-) + 2H(+) → H2 catalysis. This intermediate, obtained by treatment of Cp*Rh(bpy) (Cp*, η(5)-pentamethylcyclopentadienyl; bpy, κ(2)-2,2'-bipyridyl) with acid, is not a hydride species but rather, bears [η(4)-Cp*H] as a ligand. Delivery of a second proton to this species leads to evolution of H2 and reformation of η(5)-Cp* bound to rhodium(III). With suitable choices of acids and bases, the Cp*Rh(bpy) complex catalyzes facile and reversible interconversion of H(+) and H2.

Keywords: catalysis; hydrogen evolution; pentamethylcyclopentadienyl; proton reduction; rhodium.

Publication types

  • Research Support, Non-U.S. Gov't