Decaborane preparations

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. 

B2qH240H] anion (75). Both B2QH24OH2 and [B2qH240H] are isoelectronic with the [B qH ] anion (77). The hydropolyborate ions formed by proton abstraction from decaborane are usehil intermediates for the preparation of metaHaboranes and heteroboranes. 

The related mono-A/-alkylated carboranes, 7-(NH2R)-7-CB2qH22, can be prepared by treatment of decaborane(14) with alkyl isocyanides (125). 

The three isomeric icosahedral carboranes (76-78) are unique both in their ease of preparation and their great stability in air, and consequently their chemistry has been the most fully studied. The 1,2-isomer in particular is available on the multikilogram scale. It is best prepared in bulk by the direct reaction of ethyne with decaborane in the presence of a Lewis base, preferably Et2S ... 

Polymers derived from the preceding type of reaction with nitriles,5 amines,6 and phosphines,7 have been reported. Green8 has reported the preparation of a resin-type material composed of at least 10 repeat units from the reaction between decaborane and adiponitrile (NC(CH2)4CN). Also reported,9 is the inclusion of flexible siloxanes and ether linkages into a diamine, and of their subsequent reaction with decaborane to give adduct polymers (see 2, 3). 

Safety considerations are paramount in any boron hydride synthesis. The energy yield from the oxidations of boron hydrides is too high for any cavalier treatment of boron hydrides. Exclusion of air is the critical consideration in diborane reactions. Decaborane(14) is less reactive, generally, in a kinetic sense, but the thermodynamic potential is comparable. In addition, all volatile boron hydrides are toxic. The procedures described in the latter two preparations are within our experience non-hazardous. These procedures should be followed in every detail improvisation is not recommended. 

The o-C2Bio cage is readily prepared (Scheme 2.2-2) from acetylene by Lewis base-catalyzed reaction with mdo-decaborane(14) (Bi0Hi4), which is produced in-... 

Apart from incorporation of a silicon vertex into the decaborane skeleton by salt elimination reactions, the controlled nucleophilic degradation of the disilaborane Me2Si2BioHio with NaOH is another versatile method for the preparation of the nido-silaborate, [MeSiBioHi2], which is depicted in Scheme 3.3-9 [29]. 

Dicarbadodecaborane, preparation and structure of, 5 342-343 Dicarbomethoxy acetylene, 45 48, 49 Dicarbon decaboranes, 26 85 base degradation, 26 90 bonding, 26 62 dianions, 26 78-79 reaction with Lewis bases, 26 85 1,2-Dicarbonic acid dichlorides, 33 300 Dicarbon nonaborane anion, oxidative coupling, 26 73... 

The synthesis and characterization of the [BsHs]- ion 15,16,17) js one of the most important developments in recent years in the chemistry of pentaborane(9) and its derivatives. Several examples of a new class of pentaborane(9) derivatives have been prepared in which substituents occupy bridging sites 172-175) and significant yields of hexa-borane(lO) 16>17>, hexaborane(12) 17>, or decaborane(14) 16>17> have been obtained from the reaction of B5H8 with B2H6 by careful control of the reaction conditions. 

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). 

The search for potential BNCT drugs has re-awakened interest in the organic chemistry of the 12-vertex polyhedral boranes.1 The most widely studied chemistry is of o-carborane, where two carbon atoms are available for a number of organic reactions.2 Most substituted carboranes are prepared either by interaction of alkynes with decaborane,3 cross-coupling of Li, Na, Mg-carboranes with electrophiles 4 or by the organic reactions on the side chains (Scheme 1). ... 

The decahydrodecaborate(2 —) anion has been prepared by the reaction of triethylamine with decaborane, with... 

Decaborane(14) may be prepared with selective deuteration in several different positions. Treatment of in dioxane with D O at 25°C results in initial substitution... 

Most compounds have neutral (group VA or VIA) ligands bonded to Cu, but CuClj and [Bj Hij] yield the complex, (Et4N)j(Cl2CuBjgH,3). With [B,H, ], [BgHjjSj- and [BjjH, ] only ionic tetrakis(triphenylphosphine)Cu and -Ag salts are isolated. The decaborane CUjjBipHjp is also prepared by ... 

The preparation of a series of aminecarboranes of the type BioHi2CNH2R from decaborane and alkyl isocyanides has been reported. A more convenient preparation of this class of aminecarboranes, which gives the parent member B10H12CNH3, has also been reported. Procedures for preparation of the aminecarboranes, their methylation, and subsequent deamination of the C-(trialkylamine) carbaundecaborane(12) are described here. 

Caution. These preparations must be conducted in well-ventilated hoods. Decaborane is a very toxic material and should he handled with gloves. In addition, significant quantities of... 

This reaction should be done in a well-ventilated hood, t The decaborane is purified by sublimation at 60° and lO" mm. t The n-propyl isocyanide is prepared by the method of Jackson and McKusick/ using 490 g. (2.S mole) of n-propyl iodide and 454 g. (3.3 mole) of silver cyanide. It is observed that, after a long induction period, the reaction becomes quite violent. It is suggested that one half of the propyl iodide be added initially and the other half be added drop by drop over a 2-hour period. The drj- product is used without the final fractional distillation indicated in the reference. 

Some carboranes have formulae compatible with both classically bonded and nonclassically bonded structures and exhibit valence isomerism. The tet-racarbaborane Me4C4B6Et6 is one such. As prepared by dimerization of the small closo carborane Me2C2B3Et3 [Eq. (3.2)], it has a classical adamantane-type structure, with its four CMe units linked through BEt units (1). However, when heated it isomerizes to the expected nido carborane structure (2) with a skeletal structure like that of decaborane. ... 

You should consider attaching the -Si(CH3)2Cl substituents to the carbon atoms of this carborane using the dilithium derivative l,7-BjoH[oC2Li2. You can first prepare l,2-B]oC2Hi2 from decaborane as in the example. Then, this compound is thermally converted to a mixture of the 1,7- and 1,12-isomers, which can be separated by ch romatography ... 

The [B oHijCN] anion is prepared from decaborane(14) with aq NaCN ... 

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