Boron trihalides preparation

Amounts of very pure boron must be prepared through the thermal reduction of boron trihalides with hydrogen gas or by decomposition of BI3 using a heated tantalum wire. 

A number of boron chemicals are prepared directly from boric acid. These include synthetic inorganic borate salts, boron phosphate, fluoborates, boron trihalides, borate esters, boron carbide, and metal alloys such as ferroboron [11108-67-1]. 

Derivatives of l,2-dihydro-l,3,2-diazaborines are prepared from 2-aminobenzonitrile or 2-aminobenzamides. Compounds (147) were obtained from 2-aminobenzonitrile (148) and boron trihalides (equation 12). However, it was stated that dichlorophenylborane or... 

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... 

Exchange involving boron-halogen bonds and boron-oxygen bonds has been observed in the synthetically important reactions for the preparation of alkyldihaloboranes from alkylboroxines and boron trihalides (165, 167, 169). 

Tris(organoamino)boranes have been utilized to prepare, in reasonable yields,4,5 mono- and dihalo(organoamino)boranes which are often difficult to obtain by direct amination of the boron trihalides. Carboxylic acids, 1,3-diketones, ketones, and /3-ketoesters have been converted into carboxamides, enamino-ketones, enamines, and j -enamino-amides, respectively, by reaction with an appropriate tris(organoamino)borane under very mild conditions.6 Sulfenamides (R2NSC6H5) have also been prepared in high yield from selected tris(organoamino)boranes and sulfenic esters under relatively mild conditions.7... 

II. Preparation, Detection, and Properties of Mixed Boron Trihalide Adducts 149... 

The following methods have been used to prepare the mixed boron trihalide adducts D BX Y3 for in situ study by spectroscopic methods. 

The method of choice for the synthesis of borepins, benzoborepins, and heterole-fused borepins is reaction of the corresponding stannepins with boron trihalides or aryl dihaloboron compounds (see Section 14.20.10). A dibenzodi-hydroborepin has been prepared by a [6+l]-type cyclization of a naphthalene-1,8-diborane with BC13 (see Section 14.20.9.1). Yields of these methods are comparable. The saturated systems are typically prepared by reaction of 1,6-heptadienes with monoalkyl boranes such as thexyl borane (see Section 14.20.6.1). 

Rednction of boron trihaUdes to elemental boron can be accomplished by heating with alkali metals, alkaline earth metals, or hydrogen. Under the proper conditions, rednctions of this type can also yield diborane and, under selected conditions, boron subhalides (see below). Metal hydrides also react with boron trihalides to give diborane. Boron nitride and boron carbide have been prepared by the high-temperature reductions of boron trihalides with ammonia and methane, respectively, and deposited on metal substrates by CVD. 

These complexes, which are readily synthesized by transmetalation see Transmetalation) from the appropriate Cp metal and MX4 (L = U) or (jj -L)MX3 (L L ), represent a large family of qnite always air-stable componnds. The bromides and iodides are also obtained from chlorine exchange reactions with the appropriate boron trihalide. The flnorides can be obtained by metathesis see Metathesis) of chlorides derivatives with MesSnF. With only one equivalent of tin reagent per mole of dichloride, partial fluorination occms affording mixed hahde metallocenes. The fluorides are also prepared by chloride/fluoride, by chloride/NMe2 followed by NMe2/fluoride exchange, and by oxidative addition see Oxidative Addition). ... 

Tri(organoseleno)boranes 35 are prepared from boron trihalides and organic selenolates as stable compounds (Scheme 35) [63]. These selenoboranes have been shown to be useful for the conversion of carbonyl compounds into seleno-acetals 36 [64] and the selective ring opening of epoxides [65]. Recently, it was reported that tri(phenylseleno)borane reacts with cyclic ethers to produce m-hydroxyalkyl phenyl selenides 37 in the presence of a catalytic amount of Lewis acid [43]. 

Diborane can be prepared by a variety of methods, the most common being the reduction of boron trihalides with active metal hydrides - and the reaction of hydroborate salts with boron trifluoride, tin(II) chloride, sulfuric acid, methane-sulfonic acid, orthophosphoric acid, or polyphosphoric acid. Although diborane is commercially available in bulk quantities, we have found the reaction of potassium hydroborate, KBH4, with 85% orthophosphoric acid to be convenient for the rapid preparation in a vacuum line of small quantities of this material. ... 

Pyridazine forms a stable adduct with iodine, with semiconductor properties. " Similar complexes were prepared from iodine mono-ehloride, bromine, and nickel(II) ethyl xanthate. Complexes of pyrida-zines with iron carbonyls and with iron carbonyls and triphenylphosphine have been prepared and investigated. " Complexes of pyridazines with boron trihalides, silver salts, mercury(I) salts, iridium salts, " ruthenium salts, and chromium carbonyls are re-... 

Addition of boron trihalides to alkenes is popular, although preparative details are frequently omitted. Much of this work should be reinvestigated . The situation is much better for tetrachlorodiborane(4), B2CI4, which reacts readily with olefins to give diborylated alkanes , e.g., in the cis addition of B2CI4 to cyclohexane ... 

The classical method of preparation of amine-trihaloboranes involves the direct addition of the amine to the boron trihalide.1,2 However, when this method is used in an attempt to prepare boron trihalide adducts of secondary amines, one obtains a mixture of... 

Two further methods of preparing organoboron compounds have been the subject of fairly recent detailed study, namely, reaction of boron halides with hydrocarbons and addition of boron hydrides to olefins. For instance, arylboron dihalides are formed when boron trihalides are heated with aromatic hydrocarbons, aluminum chloride, and aluminum powder,217 and phenyl-boron dibromide has been prepared analogously.218 Further, boron halides such as diboron tetrachloride and tetrafluoride add to olefins, yielding bis-(dichloroboryl) and bis(difluoroboryl) compounds 219... 

Besides the methyl compounds a number of other alkyldiboranes have been prepared from diborane and trialkylboranes (111, 128). The alkylated diboranes can also be obtained by treating at elevated temperatures NaBH4, LiBH4, or LiAlH4 with R3B, and either u hydrogen halide or a boron trihalide (83b). 

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