Boron nitrogen hydrides

Interstitial Solid Solutions Interstitial solid solutions involve occupation of a site by introduced ions or atoms, which is normally empty in the crystal structure, and no ions or atoms are left out. Many metals form interstitial solid solutions in which small atoms (e.g., hydrogen, carbon, boron, nitrogen) enter empty interstitial sites within the host structure of the metal. Palladium metal is well known for its ability to absorb an enormous volume of hydrogen gas, and the product hydride is an interstitial sohd solution of formula PdH, 0 0.7, in which hydrogen atoms occupy... 

Figure 4.2 Proton-hydride (H- -H) distances (A) versus B-H- -H angles (degrees) in the Cambridge Structure Database for 18 x-ray structures of boron nitrogen compounds. The numbers correspond to the CSD file names, which can be found in ref. 7. (Reproduced with permission from ref. 8.)...

Boron nitrogen compounds and boron hydrides have stimulated particular theoretical interest throughout the last three decades. Some of the very simple species were investigated by FTIR methods ... 

This article covers only a part of the chemistry of boron. Boron-carbon compounds are covered in other articles in this volume see Boron Organoboranes Boron Metallacarbaboranes, and Boron Polyhedral Carboranes). The main subject of the latter two articles, and the separate one on Boron Hydrides is the extensive chemistry of the multicenter bonded boron-hydride systems. This area has been a major focus of boron research for the past 60 years. There is some direct overlap between the two articles Borides Solid-state Chemistry and Borates Solid-state Chemistry, and this more general one covering the inorganic chemistry of boron. Boron-Nitrogen Compounds are also covered separately. These articles should be consulted for more detailed discussions of the structure, bonding, and properties of borides, solid-state borates, and boron-nitrogen compounds. 

Borates Solid-state Chemistry Borides Solid-state Chemistry Boron Hydrides Boron Metallacarbaboranes Boron Nitrogen Compounds Boron Organoboranes Boron Polyhedral Carboranes. 

Discovery of the diammoniate of diborane (B2He, 2NH3) and bor-azene (B3N3H6), better known by its older name of borazole, by Stock (131) indicated that the boron hydrides could be used to prepare interesting boron-nitrogen compounds. This approach to boron chemistry was rapidly extended when the principles discussed in the preceding section were clearly recognized. Thus the compound (CH3)3N BH3, the first borane adduct to be characterized (39), pointed the way to the synthesis of a number of similar substances directly from diborane and amines for exam-... 

The element before carbon in Period 2, boron, has one electron less than carbon, and forms many covalent compounds of type BX3 where X is a monovalent atom or group. In these, the boron uses three sp hybrid orbitals to form three trigonal planar bonds, like carbon in ethene, but the unhybridised 2p orbital is vacant, i.e. it contains no electrons. In the nitrogen atom (one more electron than carbon) one orbital must contain two electrons—the lone pair hence sp hybridisation will give four tetrahedral orbitals, one containing this lone pair. Oxygen similarly hybridised will have two orbitals occupied by lone pairs, and fluorine, three. Hence the hydrides of the elements from carbon to fluorine have the structures... 

Dimethylsulfoxide Acyl and aryl halides, boron compounds, bromomethane, nitrogen dioxide, magnesium perchlorate, periodic acid, silver difluoride, sodium hydride, sulfur trioxide... 

According to B3LYP/6-31G computations of the intermediates and TSs, there are no large barriers to the reaction and it is strongly exothermic.156 Measured Ea values are around 10kcal/mol.157 The complexation of borane to the catalyst shifts electron density from nitrogen to boron and enhances the nucleophilicity of the hydride. The... 

---