Studies of a series of [Ni(PR 2NPh 2)2(CH3CN)]2+ complexes as electrocatalysts for H2 production

Substituent variation at the phosphorus atom of the P2N2 ligand

Uriah J. Kilgore, Michael P. Stewart, Monte Helm, William G. Dougherty, W. Scott Kassel, Mary Rakowski Dubois, Daniel L DuBois, R Morris Bullock

Research output: Contribution to journalArticle

102 Citations (Scopus)

Abstract

A series of [Ni(PR 2NPh 2) 2(CH3CN)](BF4)2 complexes containing the cyclic diphosphine ligands [PR 2NPh 2 = 1,5-diaza-3,7-diphosphacyclooctane; R = benzyl (Bn), n-butyl (n-Bu), 2-phenylethyl (PE), 2,4,4-trimethylpentyl (TP), and cyclohexyl (Cy)] have been synthesized and characterized. X-ray diffraction studies reveal that the cations of [Ni(PBn 2NPh 2) 2(CH3CN)](BF4)2 and [Ni(P n-Bu 2NPh 2)2(CH 3CN)](BF4)2 have distorted trigonal bipyramidal geometries. The Ni(0) complex [Ni(PBn 2NPh 2)2] was also synthesized and characterized by X-ray diffraction studies and shown to have a distorted tetrahedral structure. These complexes, with the exception of [Ni(PCy 2N Ph 2)2(CH3CN)](BF4) 2, all exhibit reversible electron transfer processes for both the Ni(II/I) and Ni(I/0) couples and are electrocatalysts for the production of H2 in acidic acetonitrile solutions. The heterolytic cleavage of H2 by [Ni(PR 2NPh 2) 2(CH3CN)](BF4)2 complexes in the presence of p-anisidine or p-bromoaniline was used to determine the hydride donor abilities of the corresponding [HNi(PR 2N Ph 2)2](BF4) complexes. However, for the catalysts with the most bulky R groups, the turnover frequencies do not parallel the driving force for elimination of H2, suggesting that steric interactions between the alkyl substituents on phosphorus and the nitrogen atom of the pendant amines play an important role in determining the overall catalytic rate.

Original languageEnglish
Pages (from-to)10908-10918
Number of pages11
JournalInorganic Chemistry
Volume50
Issue number21
DOIs
Publication statusPublished - Nov 7 2011

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electrocatalysts
Electrocatalysts
Phosphorus
phosphorus
Ligands
X ray diffraction
Atoms
ligands
diffraction
Hydrides
nitrogen atoms
hydrides
acetonitrile
Amines
atoms
Cations
cleavage
elimination
amines
electron transfer

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry

Cite this

Studies of a series of [Ni(PR 2NPh 2)2(CH3CN)]2+ complexes as electrocatalysts for H2 production : Substituent variation at the phosphorus atom of the P2N2 ligand. / Kilgore, Uriah J.; Stewart, Michael P.; Helm, Monte; Dougherty, William G.; Kassel, W. Scott; Dubois, Mary Rakowski; DuBois, Daniel L; Bullock, R Morris.

In: Inorganic Chemistry, Vol. 50, No. 21, 07.11.2011, p. 10908-10918.

Research output: Contribution to journalArticle

Kilgore, Uriah J. ; Stewart, Michael P. ; Helm, Monte ; Dougherty, William G. ; Kassel, W. Scott ; Dubois, Mary Rakowski ; DuBois, Daniel L ; Bullock, R Morris. / Studies of a series of [Ni(PR 2NPh 2)2(CH3CN)]2+ complexes as electrocatalysts for H2 production : Substituent variation at the phosphorus atom of the P2N2 ligand. In: Inorganic Chemistry. 2011 ; Vol. 50, No. 21. pp. 10908-10918.
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abstract = "A series of [Ni(PR 2NPh 2) 2(CH3CN)](BF4)2 complexes containing the cyclic diphosphine ligands [PR 2NPh 2 = 1,5-diaza-3,7-diphosphacyclooctane; R = benzyl (Bn), n-butyl (n-Bu), 2-phenylethyl (PE), 2,4,4-trimethylpentyl (TP), and cyclohexyl (Cy)] have been synthesized and characterized. X-ray diffraction studies reveal that the cations of [Ni(PBn 2NPh 2) 2(CH3CN)](BF4)2 and [Ni(P n-Bu 2NPh 2)2(CH 3CN)](BF4)2 have distorted trigonal bipyramidal geometries. The Ni(0) complex [Ni(PBn 2NPh 2)2] was also synthesized and characterized by X-ray diffraction studies and shown to have a distorted tetrahedral structure. These complexes, with the exception of [Ni(PCy 2N Ph 2)2(CH3CN)](BF4) 2, all exhibit reversible electron transfer processes for both the Ni(II/I) and Ni(I/0) couples and are electrocatalysts for the production of H2 in acidic acetonitrile solutions. The heterolytic cleavage of H2 by [Ni(PR 2NPh 2) 2(CH3CN)](BF4)2 complexes in the presence of p-anisidine or p-bromoaniline was used to determine the hydride donor abilities of the corresponding [HNi(PR 2N Ph 2)2](BF4) complexes. However, for the catalysts with the most bulky R groups, the turnover frequencies do not parallel the driving force for elimination of H2, suggesting that steric interactions between the alkyl substituents on phosphorus and the nitrogen atom of the pendant amines play an important role in determining the overall catalytic rate.",
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AU - Kilgore, Uriah J.

AU - Stewart, Michael P.

AU - Helm, Monte

AU - Dougherty, William G.

AU - Kassel, W. Scott

AU - Dubois, Mary Rakowski

AU - DuBois, Daniel L

AU - Bullock, R Morris

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