3 research outputs found
A Nickel Phosphine Complex as a Fast and Efficient Hydrogen Production Catalyst
Here
we report the electrocatalytic reduction of protons to hydrogen
by a novel S<sub>2</sub>P<sub>2</sub> coordinated nickel complex,
[Ni(bdt)(dppf)] (bdt = 1,2-benzenedithiolate, dppf = 1,1′-bis(diphenylphosphino)ferrocene).
The catalysis is fast and efficient with a turnover frequency of 1240
s<sup>–1</sup> and an overpotential of only 265 mV for half
activity at low acid concentrations. Furthermore, catalysis is possible
using a weak acid, and the complex is stable for at least 4 h in acidic
solution. Calculations of the system carried out at the density functional
level of theory (DFT) are consistent with a mechanism for catalysis
in which both protonations take place at the nickel center
A Nickel Phosphine Complex as a Fast and Efficient Hydrogen Production Catalyst
Here
we report the electrocatalytic reduction of protons to hydrogen
by a novel S<sub>2</sub>P<sub>2</sub> coordinated nickel complex,
[Ni(bdt)(dppf)] (bdt = 1,2-benzenedithiolate, dppf = 1,1′-bis(diphenylphosphino)ferrocene).
The catalysis is fast and efficient with a turnover frequency of 1240
s<sup>–1</sup> and an overpotential of only 265 mV for half
activity at low acid concentrations. Furthermore, catalysis is possible
using a weak acid, and the complex is stable for at least 4 h in acidic
solution. Calculations of the system carried out at the density functional
level of theory (DFT) are consistent with a mechanism for catalysis
in which both protonations take place at the nickel center
Catalytic Hydrogen Evolution by Fe(II) Carbonyls Featuring a Dithiolate and a Chelating Phosphine
Two pentacoordinate mononuclear iron
carbonyls of the form (bdt)Fe(CO)P<sub>2</sub> [bdt = benzene-1,2-dithiolate;
P<sub>2</sub> = 1,1′-diphenylphosphinoferrocene
(<b>1</b>) or methyl-2-{bis(diphenylphosphinomethyl)amino}acetate
(<b>2</b>)] were prepared as functional, biomimetic models for
the distal iron (Fe<sub>d</sub>) of the active site of [FeFe]-hydrogenase.
X-ray crystal structures of the complexes reveal that, despite similar
ν(CO) stretching band frequencies, the two complexes have different
coordination geometries. In X-ray crystal structures, the iron center
of <b>1</b> is in a distorted trigonal bipyramidal arrangement,
and that of <b>2</b> is in a distorted square pyramidal geometry.
Electrochemical investigation shows that both complexes catalyze electrochemical
proton reduction from acetic acid at mild overpotential, 0.17 and
0.38 V for <b>1</b> and <b>2</b>, respectively. Although
coordinatively unsaturated, the complexes display only weak, reversible
binding affinity toward CO (1 bar). However, ligand centered protonation
by the strong acid, HBF<sub>4</sub>·OEt<sub>2</sub>, triggers
quantitative CO uptake by <b>1</b> to form a dicarbonyl analogue <b>[1(H)-CO]<sup>+</sup></b> that can be reversibly converted back
to <b>1</b> by deprotonation using NEt<sub>3</sub>. Both crystallographically
determined distances within the bdt ligand and density functional
theory calculations suggest that the iron centers in both <b>1</b> and <b>2</b> are partially reduced at the expense of partial
oxidation of the bdt ligand. Ligand protonation interrupts this extensive
electronic delocalization between the Fe and bdt making <b>1(H)<sup>+</sup></b> susceptible to external CO binding