Hydrides boranes

Closely related to, but distinct from, the anionic boron and aluminum hydrides are the neutral boron (borane, BH3) and aluminum (alane, A1H3) hydrides. These molecules also contain hydrogen that can be transferred as hydride. Borane and alane differ from the anionic hydrides in being electrophilic species by virtue of the vacant p orbital and are Lewis acids. Reduction by these molecules occurs by an intramolecular hydride transfer in a Lewis acid-base complex of the reactant and reductant. 

Foremost among the elements that pack in icosahedral (and other Ar-chimedeans) structures is boron, its various hydrides (boranes), and related boron compounds (25 pp. 157-185). This topic, which is covered by numerous reviews and books, will not be further discussed in this chapter. Many other cage structures have been discussed in the literature, some of them are briefly discussed in (26). 

Fig. 1-1. The original neutral boron hydrides (boranes) isolated by Stock along with their styx numbers.

Lowe HJ, Freeman G Boron hydride (borane) intoxication in man. AMA Arch Ind Health 16 523-533, 1957... 

Cyclohexene was purchased from Wako Pure Chemical Ltd. Japan, or Aldrich Chemical Company, Inc., and used after distillation from lithium aluminum hydride. Borane-dimethyl sulfide complex was obtained from Aldrich Chemical Company, Inc., and was used as received. Trifluoromethanesulfonic acid was purchased from Wako Pure Chemical Ltd. Japan or Aldrich Chemical Company, Inc., and used without purification. The checkers used a freshly opened ampule of trifluoromethanesulfonic acid for each run. 

Boron Hydrides, Derivatives and Fuels Boron Hydrides(Boranes). These constitute a group of compds which may be represented by two generic formulas BnHn + 4 and BnHn+ 6... 

FIGFIRE 14.7 The chemical formulas of the elements in the main groups display the typical valencies of the elements. The formula of the simplest boron hydride, borane, shows it to be a dimer with empirical formula BH3. 

REDUCTION, REAGENTS Bis(N-methylpi-perazinyl)aluminum hydride. Borane-Di-methyl sulfide. Borane-Tetrahydrofurane. Borane-Pyridine. n-Butyllithium-Diisobu-tylaluminum hydride. Calcium-Amines. Diisobutylaluminum hydride. 8-Hydroxy-quinolinedihydroboronite. Lithium aluminum hydride. Lithium 9-boratabicy-clo[3.3.1]nonane. Lithium n-butyldiisopro-pylaluminum hydride. Lithium tri-j c-butylborohydride. Lithium triethylborohy-dride. Monochloroalane. Nickel boride. 2-Phenylbenzothiazoline. Potassium 9-(2,3-dimethyl-2-butoxy)-9-boratabicy-clo[3.3.1]nonane. Raney nickel. Sodium bis(2-methoxyethoxy)aluminum hydride. Sodium borohydride. Sodium borohy-dride-Nickel chloride. Sodium borohy-dride-Praeseodymium chloride. So-dium(dimethylamino)borohydride. Sodium hydrogen telluride. Thexyl chloroborane-Dimethyl sulfide. Tri-n-butylphosphine-Diphenyl disulfide. Tri-n-butyltin hydride. Zinc-l,2-Dibromoethane. Zinc borohydride. 

Binary hydride (boranes, alanes, silanes, stannanes) reductions of oxygen-containing compounds are used in organic synthesis , e.g., with ketones ... 

Alkali-metal hydrides, boranes or alanes reduce halosilanes in high yield " ... 

Alkali-metal hydrides, boranes or alanes react with alkoxysilanes or silanols to form Si—H bonds in reactions that often are preferred syntheses, depending on the availability of the silane reactant "Lithium hydride or alanate reductions used are ... 

The state of the art of reductions with metal hydrides a decade ago was the subject of comprehensive reviews. A detailed survey of reductions of carbonyl compounds with alkali and alkaline earth metal hydrides, borane and derivatives, alane and derivatives, metal borohydrides, metal aluminohydrides, silanes, stannanes and transition metal hydrides was compiled. The properties, preparation and applications of each reagent were discussed together with methods for their determination, handling techniques... 

Before discussing transition metal clusters in more detail, we will find it useful to consider compounds of boron, which has an extremely detailed cluster chemistry. As mentioned in Chapter 8, boron forms numerous hydrides (boranes) with interesting structures. Some of these compounds exhibit similarities in their bonding and structures to transition metal clusters. 

The metal hydrides exhibit different reducing properties. The complex metal hydrides (LiAlH4, NaBH4) are nucleophilic in character hydride is transported from the complex anion to the electron-deficient centers of the functional groups. Another group of metal hydrides (boranes, alanes) are strong Lewis acids they interact with centers that are relatively richer in electrons. The selectivity of the reduction can be improved and the scope of its application can be extended by the joint use of these two types (mixed hydrides). 

Boron hydrides (Boranes) and their ions. B5H9 [1493], B10H14 [1494],... 

Foremost among the elements that pack in icosahedral (and other Archimedeans) structures is boron, its various hydrides (boranes), and related boron compounds [40]. This topic, which is covered... 

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