Boron-Carbon Compounds

Hydroboration is a reaction m which a boron hydride a compound of the type R2BH adds to a carbon-carbon bond A carbon-hydrogen bond and a carbon-boron bond result... 

Thousands of compounds of the actinide elements have been prepared, and the properties of some of the important binary compounds are summarized in Table 8 (13,17,18,22). The binary compounds with carbon, boron, nitrogen, siUcon, and sulfur are not included these are of interest, however, because of their stabiUty at high temperatures. A large number of ternary compounds, including numerous oxyhaUdes, and more compHcated compounds have been synthesized and characterized. These include many intermediate (nonstoichiometric) oxides, and besides the nitrates, sulfates, peroxides, and carbonates, compounds such as phosphates, arsenates, cyanides, cyanates, thiocyanates, selenocyanates, sulfites, selenates, selenites, teUurates, tellurites, selenides, and teUurides. 

A wide range of cutting-tool materials is available. Properties, performance capabilities, and cost vary widely (2,7). Various steels (see Steel) cast cobalt alloys (see Cobalt and cobalt alloys) cemented, cast, and coated carbides (qv) ceramics (qv), sintered polycrystalline cubic boron nitride (cBN) (see Boron compounds) and sintered polycrystalline diamond tbin diamond coatings on cemented carbides and ceramics and single-crystal natural diamond (see Carbon) are all used as tool materials. Most tool materials used in the 1990s were developed during the twentieth century. The tool materials of the 1990s... 

For the most part boric acid esters are quantitated by hydrolysis in hot water followed by determination of the amount of boron by the mannitol titration (see Boron compounds, boric oxide, boric acid and borates). Separation of and measuring mixtures of borate esters can be difficult. Any water present causes hydrolysis and in mixtures, as a result of transesterification, it is possible to have a number of borate esters present. For some borate esters, such as triethanolamine borate, hydrolysis is sufftciendy slow that quantitation by hydrolysis and titration cannot be done. In these cases, a sodium carbonate fusion is necessary. 

The analogous reactions of PbCl2 with lithium l-(dimethylamino)-3,5-dimethylboratabenzene or l-[bis(trimethyl-silyl)amino]-3,5-dimethylboratabenzene yield the corresponding sandwich compounds 44 and 45. The lead atom of 45 displays a rather asymmetric bonding to the boratabenzene rings as evidenced by the fact that the lead-to-carbon/ boron distances span the large range from 2.519 to 3.033 A.7... 

Chemically, tungsten is rather inert, but it will form compounds with several other elements at high temperatures (e.g., the halogens, carbon, boron, silicon, nitrogen, and oxygen). Tungsten will corrode in seawater. 

Much is known empirically on B-NMR data (39). Restricting boron compounds to noncyclic molecules with no or one nitrogen atom and two, three, or four carbon atoms bonded to boron and omitting sterically overcrowded alkyl groups R and R, we find four classes with the following typical chemical shift ranges (Et20 BF3 as the external standard) ... 

Enyne 112a having a boron moiety on the alkyne gives vinyl boron 113a [Eq. (6.83)], whose carbon-boron bond can be converted to a carbon-carbon bond. Enyne metathesis followed by Diels-Alder reaction of the resulting diene with DMAD gives tricyclic compound 114 [Eq. (6.84)]. ... 

Fuel, oxygen, and high temperature are essential for the combustion process. Thus, polyfluorocarbons, phosphazenes, and some composites are flame-resistant because they are not good fuels. Fillers such as alumina trihydrate (ATH) release water when heated and hence reduce the temperature of the combustion process. Compounds such as sodium carbonate, which releases carbon dioxide when heated, shield the reactants from oxygen. Char, formed in some combustion processes, also shields the reactants from a ready source of oxygen and retards the outward diffusion of volatile combustible products. Aromatic polymers, such as PS, tend to char and some phosphorus and boron compounds catalyze char formation aiding in controlling the combustion process. 

Boron trichloride can be prepared by high temperature chlorination of boron trioxide, boric acid, metal borates or other boron compounds. Chlorine, hydrogen chloride, phosgene, silicon tetrachloride, metal chlorides, carbon... 

Niobium combines with carbon, boron, silicon and other elements at very high temperatures, forming interstitial binary compounds of varying compositions. With carbon, it forms niobium carbide having compositions varying from NbCo.7 to NbC [12069-94-2]. With boron, the products are orthorhombic niobium boride, NbB [12045-19-1], and the hexagonal diniobium diboride, Nb2B2[12007-29-3]. 

When selecting atom substitutions for new molecule design, chemists usually look only to the right of carbon in the periodic table. The contrarian looks to the left and finds boron—commonly viewed as a metal, but in fact quite nonmetallic in many respects. In his excellent review of boron analogues of biomolecules, Morin showed why working with boron is so attractive <94T12521>. Here are some of the unique potential applications for any new boron compound ... 

The chemistry of boron is exceedingly complex and rivals that of carbon in its diversity. Most boron compounds, however, enter or degrade in the environment to borates (B-0 compounds), such as borax and boric acid, and these are considered to be the most significant ecologically. 

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