Boron halides preparations

Amidinate- and guanidinate-substituted boron halides are normally prepared using the two standard synthetic routes, i.e., salt-metathesis between suitable... 

A third method involves elimination of chlorotrimethylsilane. This has been employed in the preparation of the bis(amidinate)-substituted boron halides... 

The Si-O-B fragment can be formed from different starting materials that generally include chlorosilanes or silanols and boron halides or boric acid derivatives. For the preparation of the cyclic six-, eight-, ten- and twelve-membered borasiloxanes 83-89 four synthetic approaches are known so far, starting from either... 

As an alternative method, poly(cyclodiborazane)s were prepared by the reaction of bis(silylimine)s with chlorodialkylboranes or with methyl dialkylborinates (scheme 18).32 This reaction proceeds via the condensation between V-silylimine and boron halide, eliminating trimethylsilyl halide followed by dimerization. However, the isolated polymer became insoluble after several hours of exposure under air, which resulted from the cross-linking reactions of unreacted trimethylsilyl groups to form trimerized hydrobenzamide derivatives. 

Extension of this reaction to electrophiles other than aldehydes was unsuccessful [22, 23], However, propargylic boronates were found to react with allylic halides and various carbonyl compounds [23], The boronates were prepared by lithiation of a methyl-substituted alkyne with t-butyllithium followed by treatment with a trialkylborane. The propargylic boronate preferentially reacts with the electrophile at the y-position to yield propargylic products (Eq. 9.20). The methodology has also been applied to alanates with comparable results. 

Bidentate boranes with an o-phenylene backbone constitute some of the simplest examples of polydentate Lewis acids with rigid backbones. They can be prepared by the reaction of boron halides with a 1,2-dimetallated benzene derivative. Thus, the reaction of 1,2-bis(chloromercurio)benzene (5) with boron trichloride affords 1,2-bis(dichloroboryl)benzene (6, Scheme 3). ... 

Boron may be prepared by several methods, such as chemical reduction of boron compounds, electrolytic reduction in nonaqueous phase, or by thermal decomposition. Many boron compounds including boron oxides, borates, boron halides, borohydrides, and fluoroborates can be reduced to boron by a reactive metal or hydrogen at high temperatures ... 

Alternatively, the compound can be prepared by heating boric oxide or boric acid with ammonium chloride or an alkali metal cyanide. Purified product can be obtained by high temperature reaction of boron halide with ammonia ... 

BC13, BBr3, and BI3 undeigo exchange reactions to yield mixed boron halides. Exchange reactions also occur with trialkyl, triaryl, trialkoxy, or triaryloxy boranes and with diborane. Anhydrous metal bromides and iodides can be prepared by the exchange reaction of the metal chloride or oxide and BBr3 or BI3 (21). 

Synthesis. One of the more common routes for the synthesis of aminoboranes involves the aminolysis of the appropriate boron halide. Trisaminoboranes are most conveniendy prepared by adding BC13 to an excess of amine in an inert solvent at low temperatures (42). For example for tris(dimethylamino)borane [4375-83-1]. ... 

The first borinate-transition metal complex to be prepared was actually the first known derivative of borin. Bis(cyclopentadienide)cobalt (94) reacts with organic halides and was analogously found to react with boron halides in a redox reaction to give (95), followed by an insertion to yield (cyclopentadienide)(borinato)cobalt (97) (72CB3413). The product composition depends on the ratio of reactants. Compound (97) is the main product (80% yield when R = Ph, X = Br) when the molar ratio between (94) and the boron halide is 2.5 1. A second and slower insertion occurs to give (28) when (97) is treated with another equivalent of the boron halide (Scheme 13). Compounds (28), (29) and (97) have one electron more than predicted by the 187r-electron rule for transition metal complexes. They are red in colour and, of course, paramagnetic. The mixed complexes (97) are thermally labile, in contrast to (28) and (29), which can be heated to 180 °C and sublimed at 90 °C. Their ionization potentials are low and the complexes are sensitive to air. 

Efforts to prepare Si—C—B materials focused on dehalocoupling mixtures of boron halides and Me2SiCl2 (equations 37 and 38). 

Aromatic boron compounds, in zinc halide preparation, 9, 92... 

Boron-sulfur bonds, addition, to alkynes, 10, 778 Boron trihalides, in boron compound synthesis, 9, 146 Boron-zinc exchange and copper-catalyzed substitutions, 9, 518 for organozinc halide preparation, 9, 89 Borostannylation, enynes, 10, 334... 

The typical preparation of the cyclic boroles from acyclic starting materials usually involves acid base chemistry or transacetalization protocols. 1,3,2-Diazaborolidines, such as 311 and 313, are readily available via the reaction of the corresponding amines 310 and 314 with boron tribromide (BBr3) and boron halide 312 (Scheme 51) <2006JCD3777>. 

One of the prominent synthetic protocols for the preparation of diazaborolines 323 involves the reaction of lithiated diamides 324 with boron halides and subsequent elimination of lithium halide salt. Another protocol involves synthesis via cyclocondensation of 1,2-diimines 325 with alkylboron halides to yield the diazaborolium salts 326 that undergo reduction with sodium amalgam yielding the diazaborolines 323 in high yield (Scheme 53) <2005EJI4715>. 

A mixture of, for instance, metal and boron halides is reduced at temperatures of 1300 to 1600 K. Borides of Ti, Zr, and Hf have been prepared according to ... 

Many compounds with B-S-R groups have been synthesized, including thioborates or trialkyl- and tiaryl-thioborates, B(SR)3, the sulfur analogs of trialkoxy- and triaryloxybo-ranes, and trialkyl- and triarylborathiins, (SBR)3, the sulfur analogs of boroxins. Simple thioborates are usually prepared by reactions of boron halides with thiols (equation 13). 

These reactions usually proceed more slowly than the reactions of the corresponding alcohols or phenols with boron halides. In some cases, where direct reaction is too slow, the lead or mercury derivatives of thiols are used. Attempts to use the reactions of thiols with diboron trisulfide to prepare trialkylthioboranes have usually been unsuccessful, although analogous reactions with oxygen compounds are commonly used to prepare trialkoxyboranes. Formation of B-S bonds... 

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