Diboranes properties

Boranes are typical species with electron-deficient bonds, where a chemical bond has more centers than electrons. The smallest molecule showing this property is diborane. Each of the two B-H-B bonds (shown in Figure 2-60a) contains only two electrons, while the molecular orbital extends over three atoms. A correct representation has to represent the delocalization of the two electrons over three atom centers as shown in Figure 2-60b. Figure 2-60c shows another type of electron-deficient bond. In boron cage compounds, boron-boron bonds share their electron pair with the unoccupied atom orbital of a third boron atom [86]. These types of bonds cannot be accommodated in a single VB model of two-electron/ two-centered bonds. 

R. F. Muraca, J. Neff, and J. S. Whittick, Physical Properties ofEiquid Oyygen D fluoride and Eiquid Diborane—M Critical Review, Report No. NASA-CR-88519, SRI-951581-4, Jet Propulsion Lab., Calif. Inst, of Tech., Pasadena, Stanford Research Inst., Menlo Park, Calif., July 1967. 

Despite the fact that many boron hydride compounds possess unique chemical and physical properties, very few of these compounds have yet undergone significant commercial exploitation. This is largely owing to the extremely high cost of most boron hydride materials, which has discouraged development of all but the most exotic appHcations. Nevertheless, considerable commercial potential is foreseen for boron hydride materials if and when economical and rehable sources become available. Only the simplest of boron hydride compounds, most notably sodium tetrahydroborate, NajBHJ, diborane(6), B2H, and some of the borane adducts, eg, amine boranes, are now produced in significant commercial quantities. 

This reaction normally takes place at 700°C and at low pressure ( < 1 Torr). Doping is accomplished by the addition of arsine, diborane, or phosphine. The addition of ozone (O3) to Reaction (6) at atmospheric pressure or sub-atmospheric pressures provides films with excellent properties. H ]... 

Smith, H. jr., and R. R. Miller Some Physical Properties of Diborane, Pentaborane and Aluminium Borohydride. T. Amer. chem. Soc. 72,1452 (1950). 

The properties of some boron hydrides along with those of other volatile hydrides are shown in Table 13.2. A very interesting reaction that diborane undergoes is one in which it reacts with double bonds in hydrocarbons. The reaction can be shown as... 

Dibismuth ditellurium selenide, 4 25 Dibismuth ditellurium sulfide, 4 25 Dibismuthenes, 4 30-31 Dibismuthines, 4 29-30 Diblock copolymers, 7 646 23 367 Diborane, 13 619, 632, 634 Diborane(6), 4 141, 142, 184-185 bonding, 4 181 economic aspects, 4 228 physical properties of, 4 184t Diboron dioxide, 4 242t Diboron trioxide, 4 242t, 246 Dibromamine, 13 103 Dibromamine-B, 13 109 N, N-Dibromamines, 13 105 Dibromamine-T, 13 109 Dibromanine, 4 319 Dibromine oxide, 4 332... 

A. Burawoy (Manchester) There is no unambiguous experimental evidence (from infrared spectra or other properties) that the bridge hydrogen atoms in diborane are in the centre of the B—H. .. B bonds formed (cf. Burawoy A. Nature Land. 1946 328 Lord Nielson J. Chem.Phys. 1981 19 1) The criticisms against the interpretation of the diborane bridge as an electrostatic hydrogen bond (Cartnell Fowles Valency and Molecular Structure p. 223 Butterworth London 1956) do not take sufficient account of the exceptionally... 

Since 1964, a large number of borane adducts have been prepared through either the direct reaction of diborane(6) with Lewis bases or through less direct procedures which involve displacement of hydride ion from BH4. Table 3 below lists most of these materials and some of their properties. 

However, the boron-11 nmr spectrum of (C4He)B2H4 116-117> clearly shows that it has structure 1 below, not structure a. Moreover, the chemical properties reported for (C4He)2B2H2 115> are not consistent with those of known tetraalkyl derivatives of diborane(6), e.g. at room temperature it does not hydroborate terminal olefins nor react with methanol. Brown and coworkers therefore proposed 114> structure 2 for (C4H6) 2B2H2. 

Silane and diborane show a high reactivity towards zeolitic hydroxyl groups. Treatment of H-zeolites with silane results in a permanent change of their structural properties. 

B. Synthesis, Structure, and Properties of Some Halogenated Diboranes. 195... 

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