TY - JOUR
T1 - Thermodynamic Hydricity of Transition Metal Hydrides
AU - Wiedner, Eric S.
AU - Chambers, Matthew B.
AU - Pitman, Catherine L.
AU - Bullock, R. Morris
AU - Miller, Alexander J.M.
AU - Appel, Aaron M.
N1 - Funding Information:
E.S.W. and A.M.A. were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. R.M.B. was supported by the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy. M.B.C. and A.J.M.M. were supported by the Division of Chemical Sciences, Geosciences & Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy through Grant DE-SC0014255. C.L.P. was supported by the National Science Foundation Center for Enabling New Technologies through Catalysis (CHE-1205189) and is a Fellow of the Royster Society.
PY - 2016/8/10
Y1 - 2016/8/10
N2 - 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.
AB - 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.
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U2 - 10.1021/acs.chemrev.6b00168
DO - 10.1021/acs.chemrev.6b00168
M3 - Review article
AN - SCOPUS:84981725584
VL - 116
SP - 8655
EP - 8692
JO - Chemical Reviews
JF - Chemical Reviews
SN - 0009-2665
IS - 15
ER -