Decaborane, pyrolysis

G in the presence of a catalytic amount of a Lewis base such as dimethylether, (GH2)20. In addition to the gas-phase pyrolysis of diborane, can be prepared by a solution-phase process developed at Union Garbide Gorp. Decaborane is a key intermediate in the preparation of many carboranes and metaHa derivatives. As of this writing, this important compound is not manufactured on a large scale in the western world and is in short supply. Prices for decaborane in 1991 were up to 10,000/kg. 

Decaborane is the most studied of all the polyhedral boranes and at one time (mid-1950s) was manufactured on a multitonne scale in the USA as a potential high-energy fuel. It is now obtainable in research quantities by the pyrolysis of B2H9 at 100-200°C in the presence of catalytic amounts of Lewis bases such as Me20. B10H14 is a colourless, volatile, crystalline solid (see Table 6.2, p. 163) which... 

Other monomeric precursors similar to 6-hexynyl-decaborane such as 6-norbornenyl-decaborane (129) and 6-cyclooctenyl-decaborane (131) (Fig. 75) underwent ROMP in the presence of either first- or second-generation Grubbs catalysts to produce the corresponding poly(norbornenyl-decaborane) (130) (Fig. 75) and poly(cyclooctenyl-decaborane) (132) (Fig. 75) with Mn > 30 kDa and polydis-persities between 1.1 and 1.8.152 Electrostatic spinning and pyrolysis of poly (norbomenyl-decaborane) was discovered to produce nanoscale, free-standing porous boron-carbide/carbon, ceramic fiber matrices.153... 

Decaborane dianion, oxidative coupling, 26 73 Decaboron decahalides, 26 13, 48 hydrogenation of chloride, 26 48 pyrolysis of dianions, 26 48 Decabromotriselenate(lI,IV), 35 290 Decadiene complexes with silver, 12 340 Decaholotellurate(IV), structure, 35 249-251 Decarbonylation, thermal, of trifluoroacetyl derivatives, 27 295-300... 

A preceramic, carrier polymer route to boron carbide has been reported via the pyrolysis of a polynorbomene that bears decaborane side groups.69 An important feature of this development is the ability to produce nanofibers of boron carbide in the following way. A solution of the poly(norbomenyldecaborane) in THF is subjected to the process of... 

Decaborane(14), the smallest solid borane and an important precursor to higher hydrides as well as carboranes (see below), was formerly prepared via diborane pyrolysis however, this approach has been rendered obsolete by the development of several high-yield routes based on the BH or B5Hg anions (the latter species is easily obtained via deprotonation of B5H9). 

Heating B2H6 above 100°C leads to pyrolysis and generates a variety of more complex boranes of which tetraborane(lO) B4H10 and decaborane( 14) B1QH14 are the most stable. Other reactions can... 

Previously, decaborane(14) was synthesized by pyrolysis of hazardous di-borane(6) in elaborate apparatus which precluded the use of the method for general laboratory work.1 The procedure given here is performed in standard glassware employing relatively safe materials and thus makes decaborane(14) generally available for the first time. 

A new heteroborane, l-thia-c/uw-decaborane(9), B9H9S, has been prepared by the pyrolysis of B9HHS at 375 °C in vacuo. It was characterized by i.r., mass, and B n.m.r. spectral data the proposed structure is (2). The compound is reasonably stable in air, and it is unattacked by water or aqueous acids and bases. 

Triammine-decaborane and NH3 give an amorphous product containing both NH and BH groups when reacted between 300 to 450°C. Below 850°C, pure BN of low crystallinity is formed, which converts to crystalline a-BN above 1180°C [59]. Boron nitride ceramics are also formed by pyrolysis of other decaborane-amine adducts [60 to 62]. 

Pyrolysis of ethylene-diborane and trimethylborane-diborane mixtures (271, 272) yields 2-alkylpentaboranes, as well as mixtures of polyalkylated pentaboranes and alkylated decaboranes. The B NMR data for the alkylated pentaboranes obtained from the ethylene-diborane reaction (271) should be reinterpreted in favor of a downfield chemical shift effect of the alkyl group. 

A second-order rate with an activation energy of 39.5 + 1 kcal/mole is observed for the decomposition of 2-ethyldecaborane at about 220° C. The initial products from this pyrolysis tre decaborane and diethyldecaboranes (297). The ionization potential (29S), infrared (299), and mass spectrum (SOO) of ethyldecaborane have been reported. 

In this chapter, method for preparing high-quality boron films by pyrolysis of decaborane in the molecular flow region at temperatures between 350 and 1200°C is described. The deposition mechanism is discussed in terms of the dependence of the deposition rate on the substrate temperature and the impingement frequency of decaborane molecules onto the substrate surface. 

In this chapter, preparation of boron films by pyrolysis of decaborane is discussed and properties of the boron films deposited are described. 

It is thought that the deposition rate of boron films obtained by pyrolysis of decaborane depends on the impingement frequency of decaborane on the substrate. From gaseous molecular dynamics, the impingement frequency S of decaborane on the substrate surface is given by... 

Figures of merit of the boron films as a function of temperature are shown in Fig. 12. The value Z increases steeply with an increase of temperature. However, the Z values of the boron films are smaller than those reported for the amorphous bulk material (47). A figure of merit higher than 10" deg" is required for the material of a practical thermoelectric converter. Figure 12 suggests that boron films deposited by pyrolysis of decaborane are useful for thermoelectric devices at over 2000 K.

Amorphous boron films have been deposited by pyrolysis of decaborane in the molecular flow region. On the assumption that the deposition rate of boron Aims is determined by the impingement frequency of the decaborane molecules onto the substrate surface, we have derived an equation for the deposition rate D at temperatures lower than 416°C. The equation, D = 7.16 X lO P exp(-39,000 / fs)(cm/s), explains the experimental results successfully. 

Dinitrile polymers satisfy these criteria and can be prepared in good yield from the condensation polymerization of deca-borane with dinitriles. Su et al. (1991) have obtained the polymer precursor by dispersing ZrO into decaborane dicyano-pentane polymer, (-BjgHj2-NC-(CH2)j-CN-). Subsequent pyrolysis of the precursor at 1450°C yielded crystalline ZrB. ... 

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