Thermodynamic Hydricity of Transition Metal Hydrides

Eric Wiedner, Matthew B. Chambers, Catherine L. Pitman, R Morris Bullock, Alexander J M Miller, Aaron Appel

Research output: Contribution to journalReview article

95 Citations (Scopus)

Abstract

Transition metal hydrides play a critical role in stoichiometric and catalytic transformations. Knowledge of free energies for cleaving metal hydride bonds enables the prediction of chemical reactivity, such as for the bond-forming and bond-breaking events that occur in a catalytic reaction. Thermodynamic hydricity is the free energy required to cleave an M-H bond to generate a hydride ion (H-). Three primary methods have been developed for hydricity determination: the hydride transfer method establishes hydride transfer equilibrium with a hydride donor/acceptor pair of known hydricity, the H2 heterolysis method involves measuring the equilibrium of heterolytic cleavage of H2 in the presence of a base, and the potential-pKa method considers stepwise transfer of a proton and two electrons to give a net hydride transfer. Using these methods, over 100 thermodynamic hydricity values for transition metal hydrides have been determined in acetonitrile or water. In acetonitrile, the hydricity of metal hydrides spans a range of more than 50 kcal/mol. Methods for using hydricity values to predict chemical reactivity are also discussed, including organic transformations, the reduction of CO2, and the production and oxidation of hydrogen.

Original languageEnglish
Pages (from-to)8655-8692
Number of pages38
JournalChemical Reviews
Volume116
Issue number15
DOIs
Publication statusPublished - Aug 10 2016

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Hydrides
Transition metals
Thermodynamics
Chemical reactivity
Free energy
Metals
Hydrogen
Protons
Ions
Oxidation
Electrons
Water

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Thermodynamic Hydricity of Transition Metal Hydrides. / Wiedner, Eric; Chambers, Matthew B.; Pitman, Catherine L.; Bullock, R Morris; Miller, Alexander J M; Appel, Aaron.

In: Chemical Reviews, Vol. 116, No. 15, 10.08.2016, p. 8655-8692.

Research output: Contribution to journalReview article

Wiedner, Eric ; Chambers, Matthew B. ; Pitman, Catherine L. ; Bullock, R Morris ; Miller, Alexander J M ; Appel, Aaron. / Thermodynamic Hydricity of Transition Metal Hydrides. In: Chemical Reviews. 2016 ; Vol. 116, No. 15. pp. 8655-8692.
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