Hydrogen bridged bond

The representation of molecular properties on molecular surfaces is only possible with values based on scalar fields. If vector fields, such as the electric fields of molecules, or potential directions of hydrogen bridge bonding, need to be visualized, other methods of representation must be applied. Generally, directed properties are displayed by spatially oriented cones or by field lines. 

Fig. 5. Modes of M—H—B bonding where M—H—B represents a three-center hydrogen bridge bond for (a), (b), (c) tetrahydroborates and for (d), (e), (f)...

Fig. 35. A very rare example of a hydrogen bridge bond involving a zinc atom, as found in the structure of H2MoCp2 ZnBr2 DMF (Ref. 164). The average Zn-H distance of 1.69 A found in this complex is, in fact, that expected for a Zn-H bridge, based on the known Zn-H (terminal) distance of 1.62 A in [HZnN(Me)-C2H4NMe2 2 (Ref. 165)...

The 3c-2e hydrogen bridged bonds of type M-H-M and M-H-B can be formed with main-group metals (such as Be, Mg and Al) and transition metals (such as Cr, W, Fe, Ta, and Zr). Some examples are shown in Fig. 11.1.1. 

Structures containing multiple hydrogen bridged bonds (a) B2H6, (b) A1(BH4)3,... 

Thixotropic agent Undergo reversible crosslinking reactions via hydrogen bridge bonds, forming a gel structure Added as the last ingredient in the formulation. Mainly used for water-based acrylics... 

CsCl-type structure, whose phase transition to a disordered phase occurs above room temperature. The hydrogen-bridge bond strength, deduced from the OH. .. FM stretching mode, was found to be 1.77 kcalmol k ODj AsFg- has been prepared similarly from DF,D20 and AsFj. The white solid contained less than 1% of OD2H AsFg as impurity. 

Saenger, W. Betzel, C. Hingerty, B. Brown, G.M. Flip-flop hydrogen bridging bonds in P-cyclodextrin—a general principle in polysaccharides. Angew. Chem. 1983, 95 (11), 883-884. 

In agreement with the equilibrium constant of this reaction, the solubility of H2O was found to be directly proportional to y Pn o nd exponentially proportional to temperature, as illustrated for industrial glasses by Fig. 76. In the case of glasses with a high content of alkali oxides (abo e 25% in binary systems) the water dissolves producing hydrogen bridge bonds. 

The suitability of a solvent for a given extraction problem can be assessed by the distribution coefficient as long as the evaluation refers to the separation of the solute. In order to elucidate the solubilities, it has to be determined whether the intermolecu-lar forces present in the liquids are caused by polar molecules with their dipolar interaction, hydrogen-bridge bonding or by non-polar molecules with van der Waals interaction. The impact of such forces is discussed in the literature [27],... 

Of special interest is the interaction of aminyloxides and solvents. A considerable influence of polarity of solvent to distribution of spin density was found. The interaction of aminyloxide group and protic solvents is defined by formation of hydrogen-bridge-bonds. For this hydrogen bridging the models A (o-model) and B (7r-model) are discussed by Buchachenko, the former being favored161. ... 

Proteins consist of 20, in some bacteria 22, different amino acids covalently linked with each other by peptide bonds. The amino acid side chains form many hydrophobic bonds, intermolecular hydrogen bridge bonds, and salt bridges within the protein chains or with another partner molecule. 

Four of the seven known metal tetrakis-borohydrides—Zr, Hf, Th, and U borohydrides (1,2)—were first synthesized about 30 years ago during the Manhattan project. They were found to be very volatile and reactive compounds. In recent years, much structural, spectroscopic, and chemical studies were done on these molecules. New tetrakis-borohydrides of the actinides Pa, Np, and Pu have recently been prepared by analogous reactions used in the syntheses of U and Th borohydrides (3). The Pa compound, Pa(BHi+K, is iso-morphous to and behaves like U(BHi+)i+ and Th(BHi+)i+ while x-ray studies on Np(BHi+)i+ and the isostructural Pu(BHi+)i+ have shown that they resemble the highly volatile Zr and Hf compounds both in structure and properties. All seven compounds contain triple hydrogen bridge bonds connecting the boron atom to the metal. 

The crystal structure of U(BHtf)if has been examined by single crystal x-ray (4b) and neutron diffraction techniques (4a). Much like the bonding in the well-known boron hydrides (11), this metal borohydride exhibits hydrogen bridge bonds that join the boron atom to the metal. In U(BHt+)i+j there are two tridentate and four... 

UCBHOit (solid, 14 coordinate, 4 double hydrogen bridge bonds, 2 triple-hydrogen-bridge bonds)... 

Silylation increases detection and raises the derivatives thermal stability. The substitution of active hydrogen leads to the higher polarity of compounds and reduces hydrogen bridge bonds, so... 

On the basis of known behavior most boron hydride reactions may be assigned to two main classes. The first class involves removal of a borane group from a boron hydride structure, while the second class involves nonsymmetrical cleavage of the hydrogen bridge bonds in a borane.2... 

More recently another mode of reaction of some of the boranes has been recognized. Certain reagents under rather carefully controlled conditions induce nonsymmetrical cleavage of the hydrogen bridge bonds. As will be discussed in more detail later (Section II,B), formation of the diammoni-ate of diborane probably involves this mechanism. 

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