An orbital analysis of hydrogen pairing in nonstoichiometric transition-metal hydrides

Halet, J.‐F.; Saillard, Jean Yves; Koudou, Claude; Minot, Christian; Nomikou, Zafiria; Hoffmann, Roald; Demangeat, C.

doi:10.1021/cm00019a031

Cited by 16 publications

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“…Other kind of bridging structures exists as in the case of the polynuclear hydride La 2 MgNi 2 H 8 27, 28. As referred by Halet et al29 different possible mechanisms to stabilize H–H interaction in solids are possible, all of them inspired by the already mentioned σ‐back donation bonding. Vargas et al30 have investigated the H occupancy on interstitial sites of fcc Nickel in the diluted solution limit.…”

Section: Resultsmentioning

confidence: 99%

“…The analysis of the density charge in the solid state exhibits the presence of a CP between hydrogen atoms. This particular H–H interaction cannot be rationalized in terms of the standard σ‐back donation mechanism24, 25 and neither does it correspond to a simple dimerization as it has been discussed in hydrogen diluted phases29, 30 or a dihydrogen bond scheme 23, 31, 33. The Westlake's criteria are not followed in this case owing to the particular low dimensionality of the H arrangement in the NiH 2 units.…”

Section: Discussionmentioning

confidence: 97%

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Hepatocellular carcinoma with main portal vein tumor thrombus

Zhang

Wang

Yan

et al. 2009

Cancer

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BACKGROUND:Hepatocellular carcinoma (HCC) with main portal vein tumor thrombus (MPVTT) is often associated with poor prognosis. We retrospectively assessed the effectiveness of percutaneous transhepatic portal vein stenting and transarterial chemoembolization (PTPVS‐TACE) combined with or without 3‐dimensional conformal radiotherapy (3‐DCRT) for HCC with MPVTT.METHODS:Forty‐five patients with HCC complicated by MPVTT were treated with PTPVS‐TACE. Among them, 16 patients (group A) received 3‐DCRT with 30‐60Gy as daily 2Gy fractions. The remaining 29 patients (group B) received no radiotherapy. The tumor responses, complications, stent patency rates, and cumulative survival rates were evaluated, and the Kaplan‐Meier method and log‐rank test were used for survival analysis.RESULTS:No severe complications were associated with PTPVS‐TACE and 3‐DCRT. The objective response rate (CR and PR) was 35.6%. The 60‐, 180‐, and 360‐day cumulative stent patency rates were 93.3%, 62.2%, and 34.6% in group A, and 58.6%, 21.7%, and 10.8% in group B, respectively, showing significant difference between the 2 groups (P < .01). The mean patency time was 475.20 ± 136.97 and 199.58 ± 61.40 days, respectively. The 60‐, 180‐, and 360‐day cumulative survival rates were 93.8%, 81.3%, and 32.5%, respectively, for group A, 86.2%, 13.8%, and 6.9%, respectively, for group B. Significant statistical differences were detected between the 2 groups (P < .01).CONCLUSIONS:These findings suggest that sequential therapy by PTPVS‐TACE‐3‐DCRT is possibly an effective treatment modality for HCC complicated by main portal vein tumor thrombus. Cancer 2009. © 2009 American Cancer Society.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 97%

Hepatocellular carcinoma with main portal vein tumor thrombus

Zhang

Wang

Yan

et al. 2009

Cancer

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“…Weak interactions of H 2 with surface species, bare metal ions, and main group Lewis acids/bases are known and will be discussed in sections 2.2.2 and 11.3. Short d HH as low as 1.5 Å (“hydrogen pairing”) are proposed to be present in certain intermetallic rare-earth hydrides, as evidenced by solid state 1 H NMR 71,72 and theoretical calculations . The observation, for example, of a characteristic splitting pattern (Pake doublet) at 140 K gives a d HH of 1.48 ± 0.02 Å in CeNiInH 1.0 , suggesting that the hydrogens may occupy nearest-neighbor tetrahedral sites separated by about 1.5 Å (2.1 Å had generally been believed to be the closest possible spacing in metal hydrides) …”

Section: Types and Synthesis Of H2 Complexesmentioning

confidence: 97%

Fundamentals of H₂Binding and Reactivity on Transition Metals Underlying Hydrogenase Function and H₂Production and Storage

2007

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Contents 1. Introduction and Historical Perspective 4152 2. Types and Synthesis of H 2 Complexes 4154 2.1. Stable H 2 Complexes 4154 2.1.1. Complexes Synthesized by Addition of H 2 Gas to an Unsaturated Precursor 4156 2.1.2. Complexes with the Most Weak, Reversible H 2 Binding and the Shortest H−H Distances 4156 2.1.3. Complexes Prepared from H 2 Gas by Ligand Displacement or Reduction 4157 2.1.4. Protonation of a Hydride Complex 4158 2.1.5. Other Methods of Preparation 4158 2.2. H 2 Complexes Unstable at Room Temperature 4158 2.2.1. Organometallic Complexes Observed at Low Temperature in Rare Gas or Other Media 4158 2.2.2. Binding of H 2 to Bare Metal Atoms, Ions, and Surfaces 4160 3. Structure and Bonding of H 2 Complexes 4160 3.1. Theoretical Analysis of Nonclassical Bonding of H 2 4160 3.2. M f H 2 Backdonation and Influence of CO Ligands on Activation of H 2 4161 4. Properties and Spectroscopic Diagnostics for H 2 Complexes 4163 4.1. Properties of H 2 Complexes 4163 4.2. Spectroscopic and Other Diagnostics for H 2 Complexes 4164 5. Vibrational Spectroscopy of H 2 Complexes 4164 6. Dynamics of H 2 and Hydride Complexes 4165 7. Thermodynamics, Kinetics, and Isotope Effects for H 2 Binding 4168 8. Biological Activation of H 2 in Hydrogenase Enzymes 4169 8.1. Introduction and Structure and Function of Hydrogenases 4169 8.2. Dihydrogen Coordination and Organometallic Chemistry Relevant to H 2 ases 4171 8.2.1. Introduction 4171 8.2.2. Formation of H 2 Ligands by Protonation and Factors That Control H 2 Binding and Activation in H 2 ases 4173 8.2.3. Heterolytic Cleavage and Acidity of H 2 Coordinated to Metal Complexes 4174 8.2.4. Intermolecular Heterolytic Cleavage of Coordinated H 2 4175 8.2.5. Intramolecular Heterolytic Cleavage of H 2 4176 8.2.6. Proton Transfer to Anions 4180 8.2.7. Strength of Binding of H 2 Compared to Water and N 2 . Importance of Entropy Effects 4180 8.2.8. Isotopic Exchange and Other Intramolecular Hydrogen Exchange Reactions 4181 8.2.9. The Need for a Low-Spin State in H 2 ases and the Possible Role of Cyanide Ligands 4183 8.2.10. Why Do Enzymes Such as H 2 ases Have Polymetallic Active Sites with Metal−Metal Bonds? 4185 8.2.11. Mechanism of Hydrogen Activation in Hydrogenases 4185 8.2.12. Summary of the above Relationships 4188 9. Hydrogen Activation in Nitrogenases 4189 10. Biomimetic Hydrogen Production 4190 11. H 2 Coordination Chemistry Relevant to Hydrogen Storage 4191 11.1. Introduction 4191 11.2. H 2 Binding to Naked Metal Ions 4192 11.3. Interaction of H 2 with Metal Surfaces, Metal Oxides and Hydrides, and Non-transition-Metal Compounds 4193 11.4. Inelastic Neutron Scattering (INS) Studies of H 2 Coordination and Rotation 4195 11.5. Binding of H 2 to Highly Porous Solids and INS Studies 4197 12. Acknowledgments 4198 13. References 4198 4152

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“…Along with increasing electronegativity of a metal, M (and the corresponding increase of the E ° value), the energy of the valence orbitals of M decreases and the orbitals become more contracted; a substantial decrease of the ionicity of the M−H bonds and a decrease of a factual negative charge on the H center result. Consequently, one could view the situation in terms of H - starting to resemble H 0 more and more as the metal's electronegativity increases, where the energy barrier for H 2 evolution, Δ E # , decreases and T dec also thereby decreases. , …”

Section: How May Tdec Be Tuned Therefore In Binary and Multinary Hydr...mentioning

confidence: 99%

Thermal Decomposition of the Non-Interstitial Hydrides for the Storage and Production of Hydrogen

2004

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Contents 1. Introduction 1283 1.1. Nomenclature and the Coverage of the Review 1284 1.2. Contents 1285 2. The Storage of Hydrogen 1286 3. Which Equilibrium Is Easier To Play On: H -I /H 2 or H +I /H 2 ? 1290 4. How Does the Thermal Decomposition of a Hydride Proceed? 1291 5. How May T dec Be Tuned, Therefore, in Binary and Multinary Hydrides of the Chemical Elements? 1293 6. Standard Enthalpy of Decomposition as an Important Predictor of T dec 1297

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An orbital analysis of hydrogen pairing in nonstoichiometric transition-metal hydrides

Cited by 16 publications

References 1 publication

Hepatocellular carcinoma with main portal vein tumor thrombus

Hepatocellular carcinoma with main portal vein tumor thrombus

Fundamentals of H₂Binding and Reactivity on Transition Metals Underlying Hydrogenase Function and H₂Production and Storage

Thermal Decomposition of the Non-Interstitial Hydrides for the Storage and Production of Hydrogen

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An orbital analysis of hydrogen pairing in nonstoichiometric transition-metal hydrides

Cited by 16 publications

References 1 publication

Hepatocellular carcinoma with main portal vein tumor thrombus

Hepatocellular carcinoma with main portal vein tumor thrombus

Fundamentals of H2Binding and Reactivity on Transition Metals Underlying Hydrogenase Function and H2Production and Storage

Thermal Decomposition of the Non-Interstitial Hydrides for the Storage and Production of Hydrogen

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Fundamentals of H₂Binding and Reactivity on Transition Metals Underlying Hydrogenase Function and H₂Production and Storage