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Title: Electrocatalytic Hydrogen Production by [Ni(7PPh2NH)2]2+: Removing the Distinction Between Endo- and Exo- Protonation Sites

Abstract

A new Ni(II) complex, [Ni(7PPh2NH)2]2+ (7PPh2NH = 3,6-triphenyl-1-aza-3,6-diphosphacycloheptane) has been synthesized, and its electrochemical properties are reported. The 7PPh2NH ligand features an NH, ensuring properly positioned protonated amine groups (N–H+) for electrocatalysis, regardless of whether protonation occurs exo- or endo- to the metal center. The compound is an electrocatalyst for H2 production in the presence of organic acids (pKa range 10–13 in CH3CN) with turnover frequencies ranging from 160–770 s-1 at overpotentials between 320–470 mV, as measured at the half peak potential of the catalytic wave. In stark contrast to [Ni(PR2NR'2)2]2+ and other [Ni(7PPh2NR')]2+ complexes, catalytic turnover frequencies for H2 production by [Ni(7PPh2NH)2]2+ do not show catalytic rate enhancement upon the addition of H2O. This finding supports the assertion that [Ni(7PPh2NH)2]2+ eliminates the distinction between the endo- and exo-protonation isomers. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Center for Molecular Electrocatalysis (CME); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1182863
Report Number(s):
PNNL-SA-104339
KC0307010
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
ACS Catalysis, 5(4):2116-2123
Additional Journal Information:
Journal Name: ACS Catalysis, 5(4):2116-2123
Country of Publication:
United States
Language:
English
Subject:
nickel phosphine; electrocatalyst; proton movement; hydrogen production

Citation Formats

Brown, Houston JS, Wiese, Stefan, Roberts, John A., Bullock, R. Morris, and Helm, Monte L. Electrocatalytic Hydrogen Production by [Ni(7PPh2NH)2]2+: Removing the Distinction Between Endo- and Exo- Protonation Sites. United States: N. p., 2015. Web. doi:10.1021/cs502132y.
Brown, Houston JS, Wiese, Stefan, Roberts, John A., Bullock, R. Morris, & Helm, Monte L. Electrocatalytic Hydrogen Production by [Ni(7PPh2NH)2]2+: Removing the Distinction Between Endo- and Exo- Protonation Sites. United States. https://doi.org/10.1021/cs502132y
Brown, Houston JS, Wiese, Stefan, Roberts, John A., Bullock, R. Morris, and Helm, Monte L. 2015. "Electrocatalytic Hydrogen Production by [Ni(7PPh2NH)2]2+: Removing the Distinction Between Endo- and Exo- Protonation Sites". United States. https://doi.org/10.1021/cs502132y.
@article{osti_1182863,
title = {Electrocatalytic Hydrogen Production by [Ni(7PPh2NH)2]2+: Removing the Distinction Between Endo- and Exo- Protonation Sites},
author = {Brown, Houston JS and Wiese, Stefan and Roberts, John A. and Bullock, R. Morris and Helm, Monte L.},
abstractNote = {A new Ni(II) complex, [Ni(7PPh2NH)2]2+ (7PPh2NH = 3,6-triphenyl-1-aza-3,6-diphosphacycloheptane) has been synthesized, and its electrochemical properties are reported. The 7PPh2NH ligand features an NH, ensuring properly positioned protonated amine groups (N–H+) for electrocatalysis, regardless of whether protonation occurs exo- or endo- to the metal center. The compound is an electrocatalyst for H2 production in the presence of organic acids (pKa range 10–13 in CH3CN) with turnover frequencies ranging from 160–770 s-1 at overpotentials between 320–470 mV, as measured at the half peak potential of the catalytic wave. In stark contrast to [Ni(PR2NR'2)2]2+ and other [Ni(7PPh2NR')]2+ complexes, catalytic turnover frequencies for H2 production by [Ni(7PPh2NH)2]2+ do not show catalytic rate enhancement upon the addition of H2O. This finding supports the assertion that [Ni(7PPh2NH)2]2+ eliminates the distinction between the endo- and exo-protonation isomers. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.},
doi = {10.1021/cs502132y},
url = {https://www.osti.gov/biblio/1182863}, journal = {ACS Catalysis, 5(4):2116-2123},
number = ,
volume = ,
place = {United States},
year = {Fri Apr 03 00:00:00 EDT 2015},
month = {Fri Apr 03 00:00:00 EDT 2015}
}

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