DIHYDROGEN BONDS -- CONTENTS -- Preface -- 1 Introduction: Weak Noncovalent Interactions -- References -- 2 Brief Summary of Hydrogen-Bonded Systems: Definitions and General View -- 2.1 Conventional Hydrogen Bonds: Theoretical and Experimental Criteria of Hydrogen Bond Formation -- 2.1.1 Energy and Geometry of Conventional Hydrogen Bonds -- 2.1.2 Cooperative and Anticooperative Energy Effects in Systems with Classical Hydrogen Bonds -- 2.1.3 Dynamics of Classical Hydrogen Bonds -- 2.2 Nonconventional Hydrogen Bonds as a Part of Hydrogen-Bonded Systems: Definition and Classification -- 2.3 Difference Between Hydrogen and Chemical Bonds -- 2.4 Concluding Remarks -- References -- 3 Concept of Dihydrogen Bonding -- 3.1 General View: From an H(2) Molecule to a Dihydrogen Bond via a Dihydrogen Ligand -- 3.2 The Nature of Dihydrogen Bonding: The Topology of Electron Density and Contributions to Total Bonding Energy -- 3.3. Scalar Spin-Spin Coupling Through Dihydrogen Bonds as Evidence of Their Partly Covalent Character -- 3.4 Field Effects on Dihydrogen Bonding -- 3.5 Pressure Effects on Dihydrogen Bonding -- 3.6 Difference Between Hydrogen and Dihydrogen Bonds -- 3.7 Concluding Remarks -- References -- 4 How to Find a Dihydrogen Bond: Experimental Criteria of Dihydrogen Bond Formation -- 4.1 Dihydrogen-Bonded Complexes in the Solid State: X-Ray and Neutron Diffraction Evidence -- 4.1.1 Topology of Electron Density in Dihydrogen-Bonded Systems from Diffraction Data -- 4.2 Gas-Phase Experiments with Dihydrogen-Bonded Complexes -- 4.3 Experiments with Dihydrogen-Bonded Complexes in Solutions -- 4.3.1 IR Spectral Criteria for the Formation of Dihydrogen-Bonded Complexes in Solutions -- 4.3.2 How to Determine the Stoichiometry of Dihydrogen-Bonded Complexes in Solution by IR Spectroscopy.

4.3.3 Energy Parameters of Dihydrogen-Bonded Complexes from IR Spectra in Solution -- 4.3.4 (1)H Nuclear Magnetic Resonance Evidence for Dihydrogen Bonding in Solution -- 4.3.5 Energy Parameters of Dihydrogen Bonds in Solution from (1)H NMR -- 4.4 Concluding Remarks -- References -- 5 Intramolecular Dihydrogen Bonds: Theory and Experiment -- 5.1 Weak Intramolecular Bonding: C-H· · ·H-C in Systems with Slightly Polarized Bonds CH -- 5.2 Intramolecular Dihydrogen Bonds in Solid Amino Acids: C-H Bonds as Weak Proton Acceptors -- 5.3 Intramolecular Dihydrogen Bonds: C-H· · ·H-B -- 5.4 Intramolecular Bonds: N-H· · ·H-B and O-H· · ·H-B -- 5.5 Intramolecular Dihydrogen Bonds in Metal Hydride Complexes -- 5.5.1 Intramolecular Dihydrogen Bonds in Metal Hydride Clusters -- 5.6 Connection Between Intramolecular Dihydrogen Bonding and Dehydrogenation Reactions -- 5.7 Concluding Remarks -- References -- 6 Intermolecular Dihydrogen-Bonded Complexes: From Groups 1A-4A to Xenon Dihydrogen-Bonded Complexes -- 6.1 Group 1A: Dihydrogen Bonds X-H· · ·H-Li and X-H· · ·H-Na (X = F, Cl, NH(3), CN, NC, HO, HS, ClCC, FCC, HCC) -- 6.2 Group 2A: Dihydrogen Bonds X-H· · ·H-Mg and X-H· · ·H-Be (X = F, Cl, Br, NH(3), NNN, CN, NC, ClCC, FCC, HCC, CH(3)CC, F(2)Be, FKr, FAr) -- 6.3 Group 3A: Dihydrogen Bonds X-H· · ·H-B, X-H· · ·H-Al, and X-H· · ·H-Ga [X = FCC, HCC, LiCC, CH(3)OH, Pr(i)OH, CF(3)OH, CF(3)CH(2)OH, CFH(2)CH(2)OH, (CF(3))(2)CHOH, (CF(3))(3)COH, CN, CH(3), Indole, Imidazole, Pyrrole, FKr, FAr] -- 6.4 Hydrides of the Elements in Group 4A Acting as Proton Acceptors and Proton Donors: Very Weak Dihydrogen Bonds -- 6.4.1 Bonds C-H, Si-H, and Ge-H in Dihydrogen Bonding -- 6.5 H-H Bonding -- 6.6 Xenon Dihydrogen-Bonded Complexes -- 6.7 Concluding Remarks -- References -- 7 Intermolecular Dihydrogen Bonding in Transition Metal Hydride Complexes.

7.1 Theoretical View of Intermolecular Dihydrogen Bonding in Transition Metal Hydride Complexes -- 7.2 Energy and Structural Parameters of Intermolecular Dihydrogen-Bonded Complexes in Solutions of Transition Metal Hydrides -- 7.3 Unusual M-H· · ·H-M Bonds -- 7.4 Concluding Remarks -- References -- 8 Correlation Relationships for Intermolecular Dihydrogen Bonds -- 8.1 General Classification of Negatively Polarized Hydrogen Atoms as Proton-Accepting Sites: Basicity Factors -- 8.2 Correlation Relationships: Energy of Formation Versus H· · ·H Distance Established for Intermolecular Dihydrogen Bonds -- 8.3 Correlation Relationships Between Energetic, Structural, and Electron Density Parameters of Intermolecular Dihydrogen-Bonded Complexes -- 8.4 Proton Affinity of Hydridic Hydrogens -- 8.5 Concluding Remarks -- References -- 9 Perspectives on Dihydrogen Bonding in Supramolecular Chemistry and Crystal Engineering -- 9.1 Concluding Remarks -- References -- 10 Dihydrogen Bonds as Intermediates in Intermolecular Proton Transfer Reactions -- 10.1 Methods Employed in Kinetic Studies of Proton Transfer to Hydridic Hydrogens -- 10.1.1 Electrochemical Experiments -- 10.1.2 Time-Dependent IR Spectra -- 10.1.3 NMR Spectra -- 10.1.4 Stopped-Flow Experiments -- 10.1.5 Theoretical Approaches -- 10.2 Proton Transfer to a Hydridic Hydrogen in the Solid State -- 10.3 Proton Transfer to a Hydride Ligand in Solutions of Transition Metal Hydride Complexes: Theory and Experiment -- 10.3.1 Kinetic Experiments with Proton Transfer to a Hydride Ligand in Solution -- 10.3.2 Proton-Hydride Exchange as a Measure of Proton Transfer to a Hydride Ligand in Solution -- 10.3.3 Proton Transfer to a Hydride Ligand in Solution: Experimental Observation of Intermediates -- 10.4 Energy Profile of Proton Transfer to a Hydride Ligand in Solution.

10.5 Energy, Intermediates, and Transition States in Intermolecular Proton Transfer to Hydridic Hydrogens: Theoretical Studies -- 10.5.1 Proton Transfer to Hydrides of the Group 3A Elements -- 10.5.2 Theory of Proton Transfer to Transition Metal Hydrides -- 10.6 Concluding Remarks -- References -- 11 General Conclusions -- 11.1 How Short or Long Can Dihydrogen Bonds Be? -- 11.2 Specific Influence of the Environment on Dihydrogen Bonding -- References -- Index.