Decaborane , production

The cyclobutadiene analogue diazadiboretidine reacts with hexafluoroacetone to give a nng expansion product [776] (equation 90) 6-(3-Fluoroaryl)decaborane is formed by alkylation of decaboranyl anion and separation of the two isomers (5- and 6-benzyl) formed by reaction with dimethyl sulfide [777] (equation 91). 

While the parent carboranes can be made from formaldehyde and decaborane, carboranes with substituents at the cage carbon can easily be synthesized from the appropriate aldehyde. For example, benzaldehyde and B10H14 give the zW(9-6-Ph-6-CB9Hn anion in 94% yield.92 The phenyl carborane formed is nido- not arachno- but subsequent carborane products can be made using similar reagents as for the parent arachno-6-CB9H14-.93... 

Figure 10 Product of the opening of aza-c/oso-decaborane and a ruthenium azaborane.

This disilaborane was an unexpected co-product in the synthesis of decaborane-alkylamine polymers. The Si2Bio cluster core consists of a distorted icosahedron in which the two silicon atoms occupy adjacent positions. The Si-Si interatomic distance is 2.308(2) A, which is slightly less than the Si-Si distance in organodisilanes (2.35 A) and the Si-B distances [2.017(3) to 2.116(3) A] are very close to the sum of the covalent radii of the two atoms (2.07 A). Further derivatives with disilaborane cluster geometry are known for the phenyl substituted compounds l,2-Ph2-doso-l,2-Si2B1oH1o and l-Me-2-Ph-doso-l,2-Si2BioHi0 [6, 7]. In addition to these disila-doso-dodecaborane clusters one example with two different group 14 elements as a part of the cluster core is known. In Scheme 3.3-2 the synthesis of this sila-stanna-doso-dodecaborate is shown. The structure of this heteroborate was determined in the solid state and the Si-Sn distance is 2.608(4) A (Scheme 3.3-2) [8]. 

Uses 1) EJ. DeLorenzo R.V. Wright, Reaction Products of Decaborane and Conjugated Diolefine , USP 3301907 (1967) CA 66, 97089 (1967) [The inventors claim that treat1 ment of B10H14 with a conjugated diolefin such as 1,3-butadiene in the presence of dialkyl ethers forms products suitable for use in solid proplnts or high energy liq fuel mixts. Thus,... 

There, are at least six definitely characterized boron hydrides, as follows diborane(6), B H tetraborane(lO), B4 H, pentaborane(9) (stable), B3 H pentaborane( 11) (unstable). B5 Hu hexaborane(lO). H10 and decaborane(14). Bio H14. In these names, note that the prefix denotes the number of boron atoms, while the figure in parentheses denotes the number of hydrogen atoms. In addition to these compounds, which are all gases or volatile liquids except decaborane(L4), decomposition of the lower boron hydrides yields colorless or yellow solid boron hydrides, ranging in composition from (BItysty to (BII). This readiness to polymerize is evidence of the reactivity of these borane compounds, which readily form additional products with ammonia, with the amalgams of the active metals, and with many otganic compounds, as well as with CO. 

In addn to these methods the Grignard reaction can be employed. For example, decaborane will react with a methyl Grignard and produce the product expected or it will react with double Grignard reagents to produce a cyclic deriv(Ref 28). Metalloboranes can be prepd from metal a-malgams, as illustrated by the following reactions (Ref 3) ... 

The isolation and identification of hexaborane(lO) and decaborane(14) from the reaction of diborane(6) with lithium octahydropentaborate(—1) was reported by Geanangel and Shore 16>. Decaborane(14) was obtained in 25 to 30 per cent yields by refluxing 1,2-dimethoxyethane solutions of the reaction products 16,178) while hexaborane(lO) was conveniently isolated in 25 to 35 per cent yields when the reaction was conducted in dimethyl ether and the products were distilled from the reaction mixture at low temperature 176-179). The reaction was initially thought to involve the unsymmetrical cleavage of diborane(6) by the octahydro-pentaborate(—1) ion because the reaction stoichiometry appeared to be 1 B2H0 to 1 BsHi and both LiBEU and Bell 10 were found among the reaction products 16>. 

The final product, c/oso-BioHioCHCR, is produced through the reaction of n/do-BioHiifCHaCN) with alkynyl pyrimidine. The arac/ino-BioHi2(CH3CN)2 results in as a kind of neat product, mdo-BioII fCIIaCN), through the reaction of decaborane with acetonitrile. 

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. 

In many catalytic processes and transition metal mediated reactions, a-bor-ane complexes have been shown to be intermediates. The bis(borane) complex Cp2Ti( 72-HBcat/)2 (HBcaT = HBcat-4-f-Bu) is a highly active catalyst for the hydroboration of vinylarenes [37]. A mechanism, shown in Scheme 3, has been proposed for the Ti-catalyzed hydroboration on the basis of a detailed mechanistic study [37]. Theoretical calculations provided further support to the proposed reaction mechanism and showed that the reductive elimination step, giving the product molecules, is rate-determining [38]. In the Cp2Ti(CO)2 catalyzed hydroboration of alkynes [36,37], the proposed reaction mechanism (Scheme 4) also involves a a-borane complex similar to 11 and 14. In the titanium-catalyzed decaborane-olefin hydroborations [47,48], a-borane complexes were also considered as intermediates. In the Cp2MH (M = Nb, Ta) mediated hydroboration reactions of olefins [39,41], Smith and his coworkers observed several interesting cr-borane complexes, such as 21-23 discussed above. 

Decaborane-16 is the fourth entry in Table XIII. This molecule consists of two square pyramids linked apex to apex by a B—B bond. The fission products, two BjHg, appear as the third entry. On comparing the listed... 

Decaborane-14 reacts with alkyl isocyanides to afford products that are considered to have a zwitterionic structure RNH - -CBioHi2] (64). The spectrum, at 32-1 Mc./sec., of the trimethyl derivative Me3NCBioHi2 is shown in the paper, but this is clearly one case in which studies at higher fields would be profitable. Some closely related ions have also been investigated by Hyatt et The spectrum... 

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