Hydrogen Generation Catalyzed by Fluorinated Diglyoxime–Iron Complexes at Low Overpotentials

Abstract

Fe II complexes containing the fluorinated ligand 1,2-bis(perfluorophenyl)ethane-1,2-dionedioxime (dAr F gH 2 ; H = dissociable proton) exhibit relatively positive Fe II/I reduction potentials. The air-stable difluoroborated species [(dAr F gBF 2 ) 2 Fe(py) 2 ] (2) electrocatalyzes H 2 generation at −0.9 V vs SCE with i cat /i p ≈ 4, corresponding to a turnover frequency (TOF) of ∼20 s −1 [Faradaic yield (FY) = 82 ± 13%]. The corresponding monofluoroborated, proton-bridged complex [(dAr F g 2 H-BF 2 )Fe(py) 2 ] (3) exhibits an improved TOF of ∼200 s −1 (i cat /i p ≈ 8; FY = 68 ± 14%) at −0.8 V with an overpotential of 300 mV. Simulations of the electrocatalytic cyclic voltammograms of 2 suggest rate-limiting protonation of an Fe "0" intermediate (k RLS ≈ 200 M −1 s −1 ) that undergoes hydride protonation to form H 2 . Complex 3 likely reacts via protonation of an Fe I intermediate that subsequently forms H 2 via a bimetallic mechanism (k RLS ≈ 2000 M −1 s −1 ). 3 catalyzes production at relatively positive potentials compared with other iron complexes.

Kinetic and thermodynamic aspects of the electrocatalysis of acid reduction in organic solvent using molecular diiron-dithiolate compounds

“…In our system, like for most of the molecular H 2 -production electrocatalysts (see e.g. [40,47,48]), we recorded peak-shaped electrocatalytic responses exhibiting current hysteresis between the forward and the return scan (Fig. 2).…”

Conformational Analysis of P,N‐Containing Eight‐Membered Heterocycles and Their Pt/Ni Complexes in Solution

“…Therefore, great efforts have been aimed at designing molecular catalysts that employ cheap and abundant metals, such as nickel, [9] cobalt, [10][11][12][13][14][15][16][17] iron, [18][19][20][21][22][23][24][25][26][27][28][29][30] or molybdenum [31][32][33] as electrocatalysts for the production and oxidation of hydrogen. [34,35] These efforts have focused on developing first-row metal complexes containing an amine base in the second coordination sphere.…”

Structural and electronic characterization of multi-electron reduced naphthalene (BIAN) cobaloximes

“…For example, in the case of the fluorinated iron diglyoxime [Fe(dArFgBF 2 ) 2 ( py) 2 ], backbone tuning permitted a remarkable change in the Fe II/I reduction potential, while retaining an analogous catalytic cycle. 39 Furthermore, a second redox peak that was detected in the case of [Co(dmgBF 2 ) 2 (MeCN) 2 ] was deemed to be a ligand based redox event. 13 The redox catalysis in this case could be achieved at either redox couple by an appropriate choice of acid.…”