Stabilization of nickel complexes with Ni 0H-N bonding interactions using sterically demanding cyclic diphosphine ligands

Eric Wiedner, Jenny Y. Yang, Shentan Chen, Simone Raugei, William G. Dougherty, W. Scott Kassel, Monte Helm, R Morris Bullock, M. Rakowski DuBois, Daniel L DuBois

Research output: Contribution to journalArticle

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Abstract

The series of complexes Ni(P tBu 2N R 2) 2, [Ni(P tBu 2N R 2) 2]BF 4, [HNi(P tBu 2N R 2) 2]BF 4, and [Co(P tBu 2N Ph 2) 2]BF 4(P tBu 2N R 2 = 1,5-dialkyl-3,7-tert-butyl-1,5-diaza-3,7-diphosphacyclooctane; alkyl = phenyl, benzyl) have been synthesized and characterized. Spectroscopic, electrochemical, and X-ray diffraction studies indicate these complexes are stable as a result of the tetrahedral arrangement of the two diphosphine ligands. Electrochemical oxidation of [HNi(P tBu 2N Ph 2) 2]BF 4 results in rapid proton transfer from nickel at a rate faster than can be observed on the CV time scale. Double protonation of Ni(P tBu 2N Bn 2) 2forms the endo-endo, endo-exo, and exo-exo isomers of [Ni(P tBu 2N BnHN Bn) 2](BF 4) 2, which were found to be more stable toward loss of H 2 than previously observed for similar complexes. The presence of Ni 0HN hydrogen bonds at the endo protonation sites of [Ni(P tBu 2N BnHN Bn) 2](BF 4) 2 results in significant differences in the Ni(I/0) oxidation potentials of each of the isomers. The differences in E 1/2(I/0) values correspond to bond free energies of 7.4 and 3.7 kcal/mol for the first and second Ni 0HN hydrogen bonds of the endo-exo and endo-endo isomers, respectively. Computational studies give bond dissociation energies of the Ni 0HN bonds that are within 1-2 kcal/mol of the experimentally determined values.

Original languageEnglish
Pages (from-to)144-156
Number of pages13
JournalOrganometallics
Volume31
Issue number1
DOIs
Publication statusPublished - Jan 9 2012

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Nickel
Isomers
isomers
Stabilization
stabilization
Protonation
nickel
Ligands
ligands
Hydrogen bonds
hydrogen bonds
Proton transfer
electrochemical oxidation
Electrochemical oxidation
interactions
Free energy
free energy
dissociation
X ray diffraction
Oxidation

ASJC Scopus subject areas

  • Organic Chemistry
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

Stabilization of nickel complexes with Ni 0H-N bonding interactions using sterically demanding cyclic diphosphine ligands. / Wiedner, Eric; Yang, Jenny Y.; Chen, Shentan; Raugei, Simone; Dougherty, William G.; Kassel, W. Scott; Helm, Monte; Bullock, R Morris; DuBois, M. Rakowski; DuBois, Daniel L.

In: Organometallics, Vol. 31, No. 1, 09.01.2012, p. 144-156.

Research output: Contribution to journalArticle

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abstract = "The series of complexes Ni(P tBu 2N R 2) 2, [Ni(P tBu 2N R 2) 2]BF 4, [HNi(P tBu 2N R 2) 2]BF 4, and [Co(P tBu 2N Ph 2) 2]BF 4(P tBu 2N R 2 = 1,5-dialkyl-3,7-tert-butyl-1,5-diaza-3,7-diphosphacyclooctane; alkyl = phenyl, benzyl) have been synthesized and characterized. Spectroscopic, electrochemical, and X-ray diffraction studies indicate these complexes are stable as a result of the tetrahedral arrangement of the two diphosphine ligands. Electrochemical oxidation of [HNi(P tBu 2N Ph 2) 2]BF 4 results in rapid proton transfer from nickel at a rate faster than can be observed on the CV time scale. Double protonation of Ni(P tBu 2N Bn 2) 2forms the endo-endo, endo-exo, and exo-exo isomers of [Ni(P tBu 2N BnHN Bn) 2](BF 4) 2, which were found to be more stable toward loss of H 2 than previously observed for similar complexes. The presence of Ni 0HN hydrogen bonds at the endo protonation sites of [Ni(P tBu 2N BnHN Bn) 2](BF 4) 2 results in significant differences in the Ni(I/0) oxidation potentials of each of the isomers. The differences in E 1/2(I/0) values correspond to bond free energies of 7.4 and 3.7 kcal/mol for the first and second Ni 0HN hydrogen bonds of the endo-exo and endo-endo isomers, respectively. Computational studies give bond dissociation energies of the Ni 0HN bonds that are within 1-2 kcal/mol of the experimentally determined values.",
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T1 - Stabilization of nickel complexes with Ni 0H-N bonding interactions using sterically demanding cyclic diphosphine ligands

AU - Wiedner, Eric

AU - Yang, Jenny Y.

AU - Chen, Shentan

AU - Raugei, Simone

AU - Dougherty, William G.

AU - Kassel, W. Scott

AU - Helm, Monte

AU - Bullock, R Morris

AU - DuBois, M. Rakowski

AU - DuBois, Daniel L

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N2 - The series of complexes Ni(P tBu 2N R 2) 2, [Ni(P tBu 2N R 2) 2]BF 4, [HNi(P tBu 2N R 2) 2]BF 4, and [Co(P tBu 2N Ph 2) 2]BF 4(P tBu 2N R 2 = 1,5-dialkyl-3,7-tert-butyl-1,5-diaza-3,7-diphosphacyclooctane; alkyl = phenyl, benzyl) have been synthesized and characterized. Spectroscopic, electrochemical, and X-ray diffraction studies indicate these complexes are stable as a result of the tetrahedral arrangement of the two diphosphine ligands. Electrochemical oxidation of [HNi(P tBu 2N Ph 2) 2]BF 4 results in rapid proton transfer from nickel at a rate faster than can be observed on the CV time scale. Double protonation of Ni(P tBu 2N Bn 2) 2forms the endo-endo, endo-exo, and exo-exo isomers of [Ni(P tBu 2N BnHN Bn) 2](BF 4) 2, which were found to be more stable toward loss of H 2 than previously observed for similar complexes. The presence of Ni 0HN hydrogen bonds at the endo protonation sites of [Ni(P tBu 2N BnHN Bn) 2](BF 4) 2 results in significant differences in the Ni(I/0) oxidation potentials of each of the isomers. The differences in E 1/2(I/0) values correspond to bond free energies of 7.4 and 3.7 kcal/mol for the first and second Ni 0HN hydrogen bonds of the endo-exo and endo-endo isomers, respectively. Computational studies give bond dissociation energies of the Ni 0HN bonds that are within 1-2 kcal/mol of the experimentally determined values.

AB - The series of complexes Ni(P tBu 2N R 2) 2, [Ni(P tBu 2N R 2) 2]BF 4, [HNi(P tBu 2N R 2) 2]BF 4, and [Co(P tBu 2N Ph 2) 2]BF 4(P tBu 2N R 2 = 1,5-dialkyl-3,7-tert-butyl-1,5-diaza-3,7-diphosphacyclooctane; alkyl = phenyl, benzyl) have been synthesized and characterized. Spectroscopic, electrochemical, and X-ray diffraction studies indicate these complexes are stable as a result of the tetrahedral arrangement of the two diphosphine ligands. Electrochemical oxidation of [HNi(P tBu 2N Ph 2) 2]BF 4 results in rapid proton transfer from nickel at a rate faster than can be observed on the CV time scale. Double protonation of Ni(P tBu 2N Bn 2) 2forms the endo-endo, endo-exo, and exo-exo isomers of [Ni(P tBu 2N BnHN Bn) 2](BF 4) 2, which were found to be more stable toward loss of H 2 than previously observed for similar complexes. The presence of Ni 0HN hydrogen bonds at the endo protonation sites of [Ni(P tBu 2N BnHN Bn) 2](BF 4) 2 results in significant differences in the Ni(I/0) oxidation potentials of each of the isomers. The differences in E 1/2(I/0) values correspond to bond free energies of 7.4 and 3.7 kcal/mol for the first and second Ni 0HN hydrogen bonds of the endo-exo and endo-endo isomers, respectively. Computational studies give bond dissociation energies of the Ni 0HN bonds that are within 1-2 kcal/mol of the experimentally determined values.

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