Decaborane reactions

The base-promoted closure of decaborane(14) yields salts of the [B qH q] anion (eq. 34). Relatively strong Lewis bases, such as trialkylamines, are required to accomplish this reaction as weaker bases, such as diethylsulfide and acetonitrile, form stable 6,9-L2B2qH22 species where L = (C2H )2S, H CCN, etc (90). 

The silacarborane analogue of C,C-dimethyl-o / o-carborane, closo-l]l-((C i]) -l]lSi[ fri [128270 8 ] h.3.s been reported (179). This o-sdacarborane, which has an icosahedral framework much like o-carborane and is reported to be stable to air and moisture, was obtained in low yield from the reaction of decaborane and bis (dimethyl amino)metbyl silane in refluxing benzene. 

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). 

The stability of the phosphine adducts is notable as is the fact that thioethers readily form such adducts whereas ethers do not. Bis-ligand adducts of moderate stability play an important role in activating decaborane for several types of reaction to be considered in moie detail in subsequent paragraphs, e.g. ... 

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 ... 

This sequence of reactions is a useful route to the pure element, but more complex boranes form when the heating is less severe. When diborane is heated to 100°C, for instance, it forms decaborane, B]0H14, a solid that melts at 100°C. Decaborane is stable in air, is oxidized by water only slowly, and is an example of the general rule that heavier boranes are less flammable than boranes of low molar mass. 

The synthesis of compounds containing boron-group IIB bonds also occurs by two pathways. The most convenient method is using anionic borane or carboranc species, as in the group-IB case, to react with Zn, Cd, or Hg halides. Moreover, reactions between organometallic compounds (Zn, Cd) with unchanged boranes arc also realized, so Zn and Cd decaboranes, e.g., MB H 2 n solvent (M = Zn, Cd), result from reactions of decaborane(14) with MRj . 

Greenwood, N. N., and /. A. McGinnety Reactions of Decaborane with Adducts of Aluminium and Gallium Hydride Chem. Comm. 1965, 331. 

The literature3 contains some limited work on decaborane-based polymer systems. Typically, most utilize the Lewis acid/base reaction between decaborane (Lewis acid, B10H12) and amines and phosphines (Lewis bases, L) resulting in the formation of complexes (see scheme 2) having the general formulas B10H12L2. For example, the... 

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 vast majority of known carboranes synthesized in the literature are derivatives of twtfo-carborane, 1,2-C2B10H12. They were synthesized from the reaction of decaborane, B10H14, with suitable alkynes in the presence of a suitable... 

The research field of ortho-carborane chemistry continues to expand rapidly mainly due to the commercial availability of ort/fo-carborane itself and the recent interest of these derivatives as agents for BNCT and other applications. Synthesis of these carboranes is still dominated by reactions of decaborane with various alkynes as shown in Table 19 (Figure 2). 3-Substituted derivatives are made by capping the /[Pg.71]

The first arachno-silaborane [MeSiB9H12(NHMe2)] was isolated from the reaction between bis(dimethylamino)-methylsilane and the dimethylsulfide adduct [ rar o-B9Hi3(SMe2)]. This silaborane cluster shows decaborane geometry with the silicon vertex in position 6 of the cluster framework.34... 

In contrast, reaction of mdo-decaborane(14) with iminoboranes RB=N R did not result in the formation of doso-azadodecaboranes (RN)(RB)BioHio because the iminoborane dimerized more rapidly and, therefore, does not insert into the Bio cluster [68]. On the other hand, the aminoiminoborane tmp-B=N-Bul reacted readily with Bi0Hi4 to give 6-(tmpH)(But)B-Bi0Hi3. Most likely, the fist step in this... 

An entry into the chemistry of mdo-decaborates is provided by utdo-B oH 4. As already mentioned, decaborane BioHi4 is easily deprotonated even in aqueous medium to yellow B10Hb and with strong bases, such as alkali metal hydrides, even further to the colorless anion B10H122-. This is summarized in the reversible reactions shown in Eq. (59). 

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-... 

The S- form of o-carboranylalanine was first synthesized in 1979 by the reaction of an optically active ethynylalanine derivative, obtained by enzymatic resolution, with decaborane(14), followed by hydrolysis (see Scheme 2.2-3) [23], Since then, several asymmetric syntheses of S- and R-enantiomers of o-carboranylalanine have been reported, including the use of stereoselective propargylation [24] and stereoselective introduction of an amino group [25],... 

The carborane 64c was characterized by a consistent set of NMR data, ab initio MO calculations, and by X-ray structure analysis [88]. The synthetic potential of 64c is indicated by its reaction with Fe(CO)3 fragments to give 69 [87]. The di-ferracarborane 69 is isostructural with nido-decaborane(14), because two BH and four BH(H) fragments were replaced by two isolobal Fe(CO)3 and four CH fragments, respectively. 

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