The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Aaron M Appel - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic hydricity of transition metal Hydrides
Chemical Reviews, 2016Co-Authors: Eric S Wiedner, Matthew B Chambers, Catherine L Pitman, Morris R Bullock, Alexander J M Miller, Aaron M AppelAbstract: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 sp...
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Thermodynamic Hydricity of Transition Metal Hydrides
Chemical reviews, 2016Co-Authors: Eric S Wiedner, Matthew B Chambers, Catherine L Pitman, Alexander J M Miller, R. Morris Bullock, Aaron M AppelAbstract: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.
Alexander J M Miller - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic hydricity of transition metal Hydrides
Chemical Reviews, 2016Co-Authors: Eric S Wiedner, Matthew B Chambers, Catherine L Pitman, Morris R Bullock, Alexander J M Miller, Aaron M AppelAbstract: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 sp...
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Thermodynamic Hydricity of Transition Metal Hydrides
Chemical reviews, 2016Co-Authors: Eric S Wiedner, Matthew B Chambers, Catherine L Pitman, Alexander J M Miller, R. Morris Bullock, Aaron M AppelAbstract: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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trialkylborane assisted co2 reduction by late transition metal Hydrides
Organometallics, 2011Co-Authors: Alexander J M Miller, Jay A Labinger, John E BercawAbstract:Trialkylborane additives promote reduction of CO2 to formate by bis(diphosphine) Ni(II) and Rh(III) Hydride complexes. The late transition metal Hydrides, which can be formed from dihydrogen, transfer Hydride to CO2 to give a formate–borane adduct. The borane must be of appropriate Lewis acidity: weaker acids do not show significant Hydride transfer enhancement, while stronger acids abstract Hydride without CO2 reduction. The mechanism likely involves a pre-equilibrium Hydride transfer followed by formation of a stabilizing formate–borane adduct.
Jun Okuda - One of the best experts on this subject based on the ideXlab platform.
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Molecular Magnesium Hydrides
Angewandte Chemie (International ed. in English), 2017Co-Authors: Debabrata Mukherjee, Jun OkudaAbstract:Solid magnesium Hydride [MgH2]∞ has been continuously pursued as a potential hydrogen storage material. Organic chemists were rather interested in soluble magnesium Hydride reagents from mid-20th century. But it was only in the last two decades that molecular magnesium Hydride chemistry received a major boost from organometallic chemists with a series of structurally well-characterized examples that continues to build a whole new class of compounds. Nearly 40 such species have been isolated, ranging from mononuclear terminal Hydrides to large Hydride clusters with more than 10 magnesium atoms. They provide not only insights into the structure and bonding of MgH motifs, but also serve as models for hydrogen storage materials. Some of them are also recognized to participate in useful catalytic transformations. An overview of these molecular magnesium Hydrides is given here, focusing on their synthesis and structural characterization.
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molecular rare earth metal Hydrides in non cyclopentadienyl environments
Angewandte Chemie, 2015Co-Authors: Waldemar Fegler, Ajay Venugopal, Mathias U Kramer, Jun OkudaAbstract:Molecular Hydrides of the rare-earth metals play an important role as homogeneous catalysts and as counterparts of solid-state interstitial Hydrides. Structurally well-characterized non-metallocene-type Hydride complexes allow the study of elementary reactions that occur at rare-earth-metal centers and of catalytic reactions involving bonds between rare-earth metals and Hydrides. In addition to neutral Hydrides, cationic derivatives have now become available.
Gerbrand Ceder - One of the best experts on this subject based on the ideXlab platform.
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First-principles study of the stability and electronic structure of metal Hydrides
Physical Review B, 2002Co-Authors: H. Smithson, A. Predith, Anton Van Der Ven, Chris A. Marianetti, D. Morgan, Gerbrand CederAbstract:A detailed analysis of the formation energies for alkali, earth-alkali, and transition-metal Hydrides is presented. The hydriding energies are computed for various crystal structures using density functional theory. The early transition metals are found to have a strong tendency for Hydride formation which decreases as one goes to the right in the transition-metal series. A detailed analysis of the changes in band structure and electron density upon Hydride formation has allowed us to understand the hydriding energy on the basis of three contributions. The first is the energy to convert the crystal structure of the metal to the structure formed by the metal ions in the Hydride (fcc in most cases). In particular, for metals with a strong bcc preference such as V and Cr, this significantly lowers the driving force for Hydride formation. A second contribution, which for some materials is dominant, is the loss of cohesive energy when the metal structure is expanded to form the Hydride. This expansion lowers the cohesive energy of the metal and is a significant impediment to form stable Hydrides for the middle to late transition metals, as they have high cohesive energies. The final contribution to the Hydride formation energy is the chemical bonding between the hydrogen and metal in which it is inserted. This is the only contribution that is negative and hence favorable to Hydride formation.
Eric S Wiedner - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic hydricity of transition metal Hydrides
Chemical Reviews, 2016Co-Authors: Eric S Wiedner, Matthew B Chambers, Catherine L Pitman, Morris R Bullock, Alexander J M Miller, Aaron M AppelAbstract: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 sp...
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Thermodynamic Hydricity of Transition Metal Hydrides
Chemical reviews, 2016Co-Authors: Eric S Wiedner, Matthew B Chambers, Catherine L Pitman, Alexander J M Miller, R. Morris Bullock, Aaron M AppelAbstract: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.