Relative hydride, proton, and hydrogen atom transfer abilities of [HM(diphosphine){sub 2}]PF{sub 6} complexes (M = Pt, Ni)

Berning, D E; Noll, B C; DuBois, D L

doi:10.1021/ja991888y

Title: Relative hydride, proton, and hydrogen atom transfer abilities of [HM(diphosphine){sub 2}]PF{sub 6} complexes (M = Pt, Ni)

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Abstract

A series of [M(diphosphine){sub 2}]X{sub 2}, [HM(diphosphine){sub 2}]X, and M(diphosphine){sub 2} complexes have been prepared for the purpose of determining the relative thermodynamic hydricities of the [HM(diphosphine){sub 2}]X complexes (M - Ni, Pt; X - BF{sub 4}, PF{sub 6}; diphosphine = bis(diphenylphosphino)ethane (dppe), bis(diethylphosphino)ethane (depe), bis(dimethylphosphino)ethane (dmpe), bis(dismethylphosphino)propane (dmpp)). Measurements of the half-wave potentials (E{sub 1/2}) for the M(II) and M(0) complexes and pK{sub a} measurements for the metal hydride complexes have been used in a thermochemical cycle to obtain quantitative thermodynamic information on the relative hydride donor abilities of the metal-hydride complexes. The hydride donor strengths vary by 23 kcal/mol and are influenced by the metal, the ligand substituents, and the size of the chelate bite of the diphosphine ligand. The best hydride donor of the complexes prepared is [HPt(dmpe){sub 2}](PF{sub 6}), a third-row transition metal with basic substituents and a diphosphine ligand with a small chelate bite. The best hydride acceptors have the opposite characteristics. X-ray diffraction studies were carried out on eight complexes: [Ni(dmpe){sub 2}](BF{sub 4}){sub 2}, [Ni(depe){sub 2}](BF{sub 4}){sub 2}, [Ni(dmpp){sub 2}](BF{sub 4}){sub 2}, [Pt(dmpp){sub 2}](PF{sub 6}){sub 2}, [Ni(dmpe){sub 2}(CH{sub 3}CN)](BF{sub 4}){sub 2}, [Ni(dmpp){sub 2}(CH{sub 3}CN)](BF{sub 4}){sub 2}, Ni(dmpp){sub 2}, and Pt(dmpp){sub 2}. The cations [Ni(dmpp){submore »« less

Authors:: Berning, D E; Noll, B C; DuBois, D L

Publication Date:: 1999-12-15

Research Org.:: National Renewable Energy Lab., Golden, CO (US)

Sponsoring Org.:: USDOE

OSTI Identifier:: 20017312

Resource Type:: Journal Article

Journal Name:: Journal of the American Chemical Society

Additional Journal Information:: Journal Volume: 121; Journal Issue: 49; Other Information: PBD: 15 Dec 1999; Journal ID: ISSN 0002-7863

Country of Publication:: United States

Language:: English

Subject:: 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; PHOSPHINES; NICKEL COMPLEXES; PLATINUM COMPLEXES; BORON FLUORIDES; PHOSPHORUS FLUORIDES; HYDROGEN TRANSFER; HYDRIDES; ELECTRONIC STRUCTURE

Citation Formats


                    Berning, D E, Noll, B C, and DuBois, D L. Relative hydride, proton, and hydrogen atom transfer abilities of [HM(diphosphine){sub 2}]PF{sub 6} complexes (M = Pt, Ni).  United States: N. p., 1999. 
        Web.  doi:10.1021/ja991888y.

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                    Berning, D E, Noll, B C, & DuBois, D L. Relative hydride, proton, and hydrogen atom transfer abilities of [HM(diphosphine){sub 2}]PF{sub 6} complexes (M = Pt, Ni).  United States.  https://doi.org/10.1021/ja991888y

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                    Berning, D E, Noll, B C, and DuBois, D L. 1999.  
        "Relative hydride, proton, and hydrogen atom transfer abilities of [HM(diphosphine){sub 2}]PF{sub 6} complexes (M = Pt, Ni)".  United States.  https://doi.org/10.1021/ja991888y.

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@article{osti_20017312,

  title        = {Relative hydride, proton, and hydrogen atom transfer abilities of [HM(diphosphine){sub 2}]PF{sub 6} complexes (M = Pt, Ni)},

  author       = {Berning, D E and Noll, B C and DuBois, D L},

  abstractNote = {A series of [M(diphosphine){sub 2}]X{sub 2}, [HM(diphosphine){sub 2}]X, and M(diphosphine){sub 2} complexes have been prepared for the purpose of determining the relative thermodynamic hydricities of the [HM(diphosphine){sub 2}]X complexes (M - Ni, Pt; X - BF{sub 4}, PF{sub 6}; diphosphine = bis(diphenylphosphino)ethane (dppe), bis(diethylphosphino)ethane (depe), bis(dimethylphosphino)ethane (dmpe), bis(dismethylphosphino)propane (dmpp)). Measurements of the half-wave potentials (E{sub 1/2}) for the M(II) and M(0) complexes and pK{sub a} measurements for the metal hydride complexes have been used in a thermochemical cycle to obtain quantitative thermodynamic information on the relative hydride donor abilities of the metal-hydride complexes. The hydride donor strengths vary by 23 kcal/mol and are influenced by the metal, the ligand substituents, and the size of the chelate bite of the diphosphine ligand. The best hydride donor of the complexes prepared is [HPt(dmpe){sub 2}](PF{sub 6}), a third-row transition metal with basic substituents and a diphosphine ligand with a small chelate bite. The best hydride acceptors have the opposite characteristics. X-ray diffraction studies were carried out on eight complexes: [Ni(dmpe){sub 2}](BF{sub 4}){sub 2}, [Ni(depe){sub 2}](BF{sub 4}){sub 2}, [Ni(dmpp){sub 2}](BF{sub 4}){sub 2}, [Pt(dmpp){sub 2}](PF{sub 6}){sub 2}, [Ni(dmpe){sub 2}(CH{sub 3}CN)](BF{sub 4}){sub 2}, [Ni(dmpp){sub 2}(CH{sub 3}CN)](BF{sub 4}){sub 2}, Ni(dmpp){sub 2}, and Pt(dmpp){sub 2}. The cations [Ni(dmpp){sub 2}]{sup 2+} and [Pt(dmpp){sub 2}]{sup 2+}exhibit significant tetrahedral distortions from a square-planar geometry arising from the larger chelate bite of dmpp compared to that of dmpe. This tetrahedral distortion produces a decrease in the energy of the lowest unoccupied molecular orbital of the [M(dmpp){sub 2}]{sup 2+} complexes, stabilizes the +1 oxidation state, and makes the [HM(dmpp){sub 2}]{sup +} complexes poorer hydride donors than their dmpe analogues. Another interesting structural feature is the shortening of the M-P bond upon reduction from M(II) to M(0).},

  doi          = {10.1021/ja991888y},

  url          = {https://www.osti.gov/biblio/20017312},
  journal      = {Journal of the American Chemical Society},

  issn         = {0002-7863},

  number       = 49,

  volume       = 121,

  place        = {United States},

  year         = {1999},

  month        = {12}

}

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