Carborane Derivatives

Main Group Element Carborane Derivatives. Main group element carborane derivatives have been reviewed (231). Only a few alkaline-earth element metaHacarborane derivatives have been characterized. The icosahedral beryUacarborane, /(9j (9-3-[(CH3)3N]-3,l,2-BeC2B H, shown in Figure 24a, has been prepared via the reaction of nido-1 and Be(CH3)2 [0(C2H3)2]2 followed by reaction of the diethyletherate product and... 

Treatment of a carborane derivative of thiirane with A-bromosuccinimide gives a j3-bromodisulfide (79MI50601). Chlorination of CM-2,3-di-f-butylthiirane by f-butyl hypochlorite proceeded differently to the reaction with chlorine itself (Scheme 41) (74JA3146). 

Cu ( j -C5H5)2] is not. Likewise, Fe and Ni carborane derivatives are extremely stable. Conversely, metallocarboranes tend to stabilize lower oxidation states of early transition elements and complexes are well established for Ti", Zr , Hf , V , Cr and Mn" these do not react with H2, N2, CO or PPh3 as do cyclopentadienyl derivatives of these elements. 

The biradical catalysts described previously for double-base propints (Ref 80) are also effective for hydrocarbon propints. Table 34 shows how p,p,-biphenylene-bis(diphenylmethyl) compares to n butyl ferrocene as a catalyst in a carboxy-terminated polybutadiene. These catalysts are claimed to overcome all of the processing difficulties, chemical stability and volatility disadvantages attributed to catalysts based on ferrocene and carborane derivatives. Another somewhat similar functioning catalyst, the free radical compd, 2,2-diphenylpicrylhydrazyl,... 

A final class of high burning rate proplnts combines the high density and high impulse difluoramino compds in their binders with the carborane derivatives. Jones (Ref 79) described the preparation of TVOPA (1,2,3-tris [1,2-bis-(difluoramino)ethoxy] propane, 1PCA (1-iso-propenyl-carboranyl-acetone) and NFPA (2,3-bis(difluoramino) propyl acrylate) and proplnts... 

Halide abstraction reactions with these carborane derivatives gives sometimes intermediate products rather than metathesis, as in the reaction of Ag(6,7,8,9,10-Br5CB9H5)(r/2-C7I Ix) with [IrCl(CO)(PPh3)] that yields an Ir—Ag adduct (238),1350 or the reaction of [MoCpI(CO)3] with Ag(CBnH12) which gives (239).I357 135 ... 

An alternative route to poly(m-carborane-siloxane) rubbers is via the condensation reaction between w-carborane di-hydrocarbyl-disilanol and a bis-ureidosilane.20 This mild reaction allows the incorporation of desired groups into the polymer via both the dihydrocarbyl-disilanol and the bis-ureidosilane (see scheme 8). The first step involves the formation of the carborane silanol from the butyl lithium carborane derivative. The bis-ureidosilane is prepared from the phenyl isocyanate (see step 2), and the final step involves reacting the dihydrocarbyl-disilanol with bis-ureidosilane. 

The nitrate was reported as being extremely unstable and detonated on heating, presumably due in part to the electron-withdrawing nature of the carborane. However, the reaction between nitric acid and either phenyl- or hydroxymethyl-o-carborane derivatives yields products where the position of nitration is directed... 

A new deboronating agent for icosahedral carboranes, dry tetrabutylammonium fluoride (TBAF), was found to degrade some small carboranes, ortho- and t( / -carborane(COMC (1995 ) 6.2.4.6).55 As it was clear that water plays a part in the process, this reagent in its wet form was used to deboronate a large number of z< /alcoholic potassium hydroxide for effective deboronation of meta-... 

Table 19 Synthetic routes to c/oso-1, 2-C2BioH- 2 (ortho-carborane) derivatives from decaborane and alkynes...

Table 20 Synthetic routes to closo-1,2-C2B10H12 (ortho-carborane) derivatives from 7,8-C2B9H12 anions...

Table 21 C-H to C-X and B-H to B-X conversions in closo-1,2-C2B10H-i2 (ortho-carborane) derivatives... 

Table 24 Structures of c/oso-1, 7-C2BioH12 (mefa-carborane) derivatives determined experimentally by X-ray diffraction unless otherwise stated ...

Constrained-geometry heterocarbaboranes with silicon and germanium have been synthesized in moderate yield starting with the o-carborane derivative r,/6u,o-l-(CH2OH)-2-(Me)-l,2-C2B1oH10.47... 

Scheme 3.2-40. Et2 BH-catalyzed condensation arachno-C6B6 carborane derivative 76, of which reactions of three borylated C2-units (see 77) the structure differs greatly from that of the in the hydride bath , starts from bis- parent compound C6B6Hi2 78.

A lovely recent result is the confinement of a carborane derivative bearing two long alkyl chains within a SWCNT, Figure 15.36.59 The vapourised carborane was allowed to diffuse into the nanotube in a vacuum. Using TEM the molecular motions of the included molecule can be followed in breathtaking... 

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