Concept of Dihydrogen Bonding

Following our general classification of hydrogen bonds, a negatively polarized hydrogen atom in H-Y, where Y is a less electronegative element than H (e.g., B, Al, Re, K, Mg, etc.), could be considered an unusual or nonconventional proton acceptor. Then the interaction 

Dihydrogen Bonds Principles, Experiments, and Applications, By Vladimir I. Bakhmutov Copyright 2008 John Wiley Sons, Inc. 

GENERAL VIEW FROM AN H2 MOLECULE TO A DIHYDROGEN BOND VIA A DIHYDROGEN LIGAND 

As mentioned in Chapter 2, the difference between a covalent chemical bond and a hydrogen bond is only quantitative, despite the dramatic difference in 

In the framework of AIM theory, which well be used extensively to describe dihydrogen bonds, the situation above corresponds to the electron density distribution in the H2 molecule, where the pc parameter takes the very large value 1.857 au and the Laplacian, V pc, is strongly negative ( —34.15 au). These data have been obtained by ab initio calculations at the MP2/6-31G level [4], 

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Similarly to classical hydrogen bonding, the nature of dihydrogen bonds can be represented clearly in the framework of the AIM concept [15], In the context... 

When correlation relationships imply a deep physical context, they become a good basis for the development of new, more common concepts or for the systematization of compounds, their properties, reactions, and even phenomena. Such relationships characterizing dihydrogen bonds are the focus of the chapter. 

This chapter consists of the application of the symmetry concepts of Chapter 2 to the construction of molecular orbitals for a range of diatomic molecules. The principles of molecular orbital theory are developed in the discussion of the bonding of the simplest molecular species, the one-electron dihydrogen molecule-ion, H2+, and the simplest molecule, the two-electron dihydrogen molecule. Valence bond theory is introduced and compared with molecular orbital theory. The photo-electron spectrum of the dihydrogen molecule is described and interpreted. 

The concept of the proton-hydride interaction or dihydrogen bonding (DHB) was generalized by Morris ... 

The observation of this intermediate, which is in the equilibrium with the dihydrogen bonded complex 2 and the free cation 3 (Scheme 2), greatly contributes to the knowledge of the detailed mechanism of the proton transfer process to transition metal hydrides and is in accordance with the concept of proton transfer to metal atoms in organometallic complexes [19c, 21a, 24a]. 

According to the valence bond order concept as applied to the case of stretched H2 complexes by Limbach, there is a significant H-H bond order phh even at /hh = 1.6 A, implying that stretched dihydrogen complexes are not usefully considered as compressed dihydrides . 

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