Abstract
The intra- and intermolecular deprotonation reactions of [(Cp C 5 F 4 N )Fe(P Et N R ′ P Et )H] + (P Et N R ′ P Et = (Et 2 PCH 2 ) 2 NR′) complexes are rate-limiting processes in the electrocatalytic oxidation of hydrogen and can be mediated by an amine base in the outer coordination sphere (OCS) by facilitating the matching of energy of deprotonation intermediates. A series of complexes with different N-substituents (R′ = Me, Et, CH 2 OMe, CH 2 N(Ph)Me, and (CH 2 ) n NMe 2 ; n = 1-4) was examined computationally using density functional theory to determine the influence of the identity and proximity of the OCS base on the intramolecular deprotonation. Complexes with an OCS dimethylamino substituent were the most suitably energy matched. The number of carbon atoms between the secondary and OCS nitrogen atoms dictated the strength of the hydrogen-bonding interaction and ring strain following deprotonation of the iron hydride. The previously reported [(Cp C 5 F 4 N )Fe(P Et N R ′ P Et )H] + (R′ = (CH 2 ) 3 NMe 2 ) electrocatalyst was predicted to have the most favorable free energy (ΔG) and free energy of activation (ΔG ∂ ). To verify the computational results, two of the iron precatalysts, (Cp C 5 F 4 N )Fe(P Et N (CH 2 ) n NMe 2 P Et )Cl (n = 2 and 4), were synthesized, and their electrocatalytic activity for the oxidation of hydrogen was determined under an atmosphere of H 2 using DABCO as the exogenous base. Maximum turnover frequencies of 270 and 200 s -1 were measured when n = 2 and 4, respectively, validating the computational results.
| Original language | English |
|---|---|
| Pages (from-to) | 1391-1396 |
| Number of pages | 6 |
| Journal | Organometallics |
| Volume | 38 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - Mar 25 2019 |
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ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry
Cite this
Outer Coordination Sphere Proton Relay Base and Proximity Effects on Hydrogen Oxidation with Iron Electrocatalysts. / Kumar, Neeraj; Darmon, Jonathan M.; Weiss, Charles J.; Helm, Monte; Raugei, Simone; Bullock, R Morris.
In: Organometallics, Vol. 38, No. 6, 25.03.2019, p. 1391-1396.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Outer Coordination Sphere Proton Relay Base and Proximity Effects on Hydrogen Oxidation with Iron Electrocatalysts
AU - Kumar, Neeraj
AU - Darmon, Jonathan M.
AU - Weiss, Charles J.
AU - Helm, Monte
AU - Raugei, Simone
AU - Bullock, R Morris
PY - 2019/3/25
Y1 - 2019/3/25
N2 - The intra- and intermolecular deprotonation reactions of [(Cp C 5 F 4 N )Fe(P Et N R ′ P Et )H] + (P Et N R ′ P Et = (Et 2 PCH 2 ) 2 NR′) complexes are rate-limiting processes in the electrocatalytic oxidation of hydrogen and can be mediated by an amine base in the outer coordination sphere (OCS) by facilitating the matching of energy of deprotonation intermediates. A series of complexes with different N-substituents (R′ = Me, Et, CH 2 OMe, CH 2 N(Ph)Me, and (CH 2 ) n NMe 2 ; n = 1-4) was examined computationally using density functional theory to determine the influence of the identity and proximity of the OCS base on the intramolecular deprotonation. Complexes with an OCS dimethylamino substituent were the most suitably energy matched. The number of carbon atoms between the secondary and OCS nitrogen atoms dictated the strength of the hydrogen-bonding interaction and ring strain following deprotonation of the iron hydride. The previously reported [(Cp C 5 F 4 N )Fe(P Et N R ′ P Et )H] + (R′ = (CH 2 ) 3 NMe 2 ) electrocatalyst was predicted to have the most favorable free energy (ΔG) and free energy of activation (ΔG ∂ ). To verify the computational results, two of the iron precatalysts, (Cp C 5 F 4 N )Fe(P Et N (CH 2 ) n NMe 2 P Et )Cl (n = 2 and 4), were synthesized, and their electrocatalytic activity for the oxidation of hydrogen was determined under an atmosphere of H 2 using DABCO as the exogenous base. Maximum turnover frequencies of 270 and 200 s -1 were measured when n = 2 and 4, respectively, validating the computational results.
AB - The intra- and intermolecular deprotonation reactions of [(Cp C 5 F 4 N )Fe(P Et N R ′ P Et )H] + (P Et N R ′ P Et = (Et 2 PCH 2 ) 2 NR′) complexes are rate-limiting processes in the electrocatalytic oxidation of hydrogen and can be mediated by an amine base in the outer coordination sphere (OCS) by facilitating the matching of energy of deprotonation intermediates. A series of complexes with different N-substituents (R′ = Me, Et, CH 2 OMe, CH 2 N(Ph)Me, and (CH 2 ) n NMe 2 ; n = 1-4) was examined computationally using density functional theory to determine the influence of the identity and proximity of the OCS base on the intramolecular deprotonation. Complexes with an OCS dimethylamino substituent were the most suitably energy matched. The number of carbon atoms between the secondary and OCS nitrogen atoms dictated the strength of the hydrogen-bonding interaction and ring strain following deprotonation of the iron hydride. The previously reported [(Cp C 5 F 4 N )Fe(P Et N R ′ P Et )H] + (R′ = (CH 2 ) 3 NMe 2 ) electrocatalyst was predicted to have the most favorable free energy (ΔG) and free energy of activation (ΔG ∂ ). To verify the computational results, two of the iron precatalysts, (Cp C 5 F 4 N )Fe(P Et N (CH 2 ) n NMe 2 P Et )Cl (n = 2 and 4), were synthesized, and their electrocatalytic activity for the oxidation of hydrogen was determined under an atmosphere of H 2 using DABCO as the exogenous base. Maximum turnover frequencies of 270 and 200 s -1 were measured when n = 2 and 4, respectively, validating the computational results.
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U2 - 10.1021/acs.organomet.8b00805
DO - 10.1021/acs.organomet.8b00805
M3 - Article
VL - 38
SP - 1391
EP - 1396
JO - Organometallics
JF - Organometallics
SN - 0276-7333
IS - 6
ER -