2 research outputs found
Proposed Ligand-Centered Electrocatalytic Hydrogen Evolution and Hydrogen Oxidation at a Noninnocent Mononuclear Metal–Thiolate
The
noninnocent coordinatively saturated mononuclear metal–thiolate
complex ReL<sub>3</sub> (L = diphenylphosphinobenzenethiolate) serves
as an electrocatalyst for hydrogen evolution or hydrogen oxidation
dependent on the presence of acid or base and the applied potential.
ReL<sub>3</sub> reduces acids to H<sub>2</sub> in dichloromethane
with an overpotential of 380 mV and a turnover frequency of 32 ±
3 s<sup>–1</sup>. The rate law displays a second-order dependence
on acid concentration and a first-order dependence on catalyst concentration
with an overall third-order rate constant (<i>k</i>) of
184 ± 2 M<sup>–2</sup> s<sup>–1</sup>. Reactions
with deuterated acid display a kinetic isotope effect of 9 ±
1. In the presence of base, ReL<sub>3</sub> oxidizes H<sub>2</sub> with a turnover frequency of 4 ± 1 s<sup>–1</sup>. The
X-ray crystal structure of the monoprotonated species [ReÂ(LH)ÂL<sub>2</sub>]<sup>+</sup>, an intermediate in both catalytic H<sub>2</sub> evolution and oxidation, has been determined. A ligand-centered
mechanism, which does not require metal hydride intermediates, is
suggested based on similarities to the redox-regulated, ligand-centered
binding of ethylene to ReL<sub>3</sub>
Proposed Ligand-Centered Electrocatalytic Hydrogen Evolution and Hydrogen Oxidation at a Noninnocent Mononuclear Metal–Thiolate
The
noninnocent coordinatively saturated mononuclear metal–thiolate
complex ReL<sub>3</sub> (L = diphenylphosphinobenzenethiolate) serves
as an electrocatalyst for hydrogen evolution or hydrogen oxidation
dependent on the presence of acid or base and the applied potential.
ReL<sub>3</sub> reduces acids to H<sub>2</sub> in dichloromethane
with an overpotential of 380 mV and a turnover frequency of 32 ±
3 s<sup>–1</sup>. The rate law displays a second-order dependence
on acid concentration and a first-order dependence on catalyst concentration
with an overall third-order rate constant (<i>k</i>) of
184 ± 2 M<sup>–2</sup> s<sup>–1</sup>. Reactions
with deuterated acid display a kinetic isotope effect of 9 ±
1. In the presence of base, ReL<sub>3</sub> oxidizes H<sub>2</sub> with a turnover frequency of 4 ± 1 s<sup>–1</sup>. The
X-ray crystal structure of the monoprotonated species [ReÂ(LH)ÂL<sub>2</sub>]<sup>+</sup>, an intermediate in both catalytic H<sub>2</sub> evolution and oxidation, has been determined. A ligand-centered
mechanism, which does not require metal hydride intermediates, is
suggested based on similarities to the redox-regulated, ligand-centered
binding of ethylene to ReL<sub>3</sub>