Electrochemical oxidation of H2 catalyzed by ruthenium hydride complexes bearing P2N2 ligands with pendant amines as proton relays

Tianbiao Liu, Mary Rakowski Dubois, Daniel L DuBois, R Morris Bullock

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Two Ru hydride complexes, Cp∗Ru(PPh 2NBn 2)H (1-H) and Cp∗Ru(PtBu 2NBn 2)H (2-H) supported by cyclic PR 2NR' 2 ligands (Cp∗ = η5-C5Me5; PR 2NBn 2 = 1,5-dibenzyl,-3,7-R-1,5-diaza-3,7-diphosphacyclooctane, where R = Ph or tBu) have been developed as electrocatalysts for oxidation of H2 (1.0 atm, 22 °C). The turnover frequency of 2-H is 1.2 s-1 at 22 °C (1.0 atm H2) with an overpotential at Ecat/2 of 0.5 V in the presence of exogenous base, DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), while catalysis by 1-H has a turnover frequency of 0.6 s-1 and an overpotential of 0.6 V at Ecat/2. Addition of H2O facilitates oxidation of H2 by 2-H and increases its turnover frequency to 1.9 s-1, while H2O slows down the catalysis by 1-H. In addition, studies of Cp∗Ru(dmpm)H (where dmpm = bis(dimethylphosphino)methane), a control complex lacking pendent amines in its diphosphine ligand, confirms the critical roles of the pendant amines of the P2N2 ligands as proton relays in the oxidation of H2.

Original languageEnglish
Pages (from-to)3630-3639
Number of pages10
JournalEnergy and Environmental Science
Volume7
Issue number11
DOIs
Publication statusPublished - Nov 1 2014

Fingerprint

Bearings (structural)
ruthenium
Ruthenium
Electrochemical oxidation
Hydrides
ligand
Amines
Protons
turnover
Ligands
catalysis
oxidation
Oxidation
Catalysis
Hydrogen
Electrocatalysts
Methane
methane
amine

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Environmental Chemistry
  • Pollution
  • Nuclear Energy and Engineering

Cite this

Electrochemical oxidation of H2 catalyzed by ruthenium hydride complexes bearing P2N2 ligands with pendant amines as proton relays. / Liu, Tianbiao; Dubois, Mary Rakowski; DuBois, Daniel L; Bullock, R Morris.

In: Energy and Environmental Science, Vol. 7, No. 11, 01.11.2014, p. 3630-3639.

Research output: Contribution to journalArticle

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AB - Two Ru hydride complexes, Cp∗Ru(PPh 2NBn 2)H (1-H) and Cp∗Ru(PtBu 2NBn 2)H (2-H) supported by cyclic PR 2NR' 2 ligands (Cp∗ = η5-C5Me5; PR 2NBn 2 = 1,5-dibenzyl,-3,7-R-1,5-diaza-3,7-diphosphacyclooctane, where R = Ph or tBu) have been developed as electrocatalysts for oxidation of H2 (1.0 atm, 22 °C). The turnover frequency of 2-H is 1.2 s-1 at 22 °C (1.0 atm H2) with an overpotential at Ecat/2 of 0.5 V in the presence of exogenous base, DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), while catalysis by 1-H has a turnover frequency of 0.6 s-1 and an overpotential of 0.6 V at Ecat/2. Addition of H2O facilitates oxidation of H2 by 2-H and increases its turnover frequency to 1.9 s-1, while H2O slows down the catalysis by 1-H. In addition, studies of Cp∗Ru(dmpm)H (where dmpm = bis(dimethylphosphino)methane), a control complex lacking pendent amines in its diphosphine ligand, confirms the critical roles of the pendant amines of the P2N2 ligands as proton relays in the oxidation of H2.

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