Mercurials boron halides

Diorgano tellurium dihalides form complexes with iodine and interhalogen compounds organic compounds with N, P, O, S, and Se donor atoms boron, aluminum, and gallium trihalides antimony pentachloride and mercury(II) halides. 

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... 

The monoaryl boric acids, RB(OH)2, arc usually isolated, as stated al >o x, l)y the action of water on the type RBXg, aitliough in certain cases this leads to the formation of the oxide RBO. The phenyl eom >ound has l)ecn obtained b " boiling with water the product of reaction from magnesium phenyl bromide and boron trifluoride. The most remarkable feature of the type RE(OH)2 is that the action of iiiercuric chloride upon them leads to the production of mercury aryl halides (RHgX). The anisyl and phenetyl compounds do not yield oxides when heated, or form salts, and tlie jS-naphthyl acid exists in two modifications. Dehydration of the acids in maw gives the oxides, RBO. 

Born tribromide is used as received. It is photosensitive, but can be purified by storage over elemental mercury, followed by storage in the dark. The use of the boron halides BF, and BCl, results in much lower yields and dilTiculties with purification, and they are therefore considered to be unsatisfactory for this reaction. 

AMMONIA GAS (7664-41-7) Anhydrous, compressed gas or cryogenic liquid. Difficult to ignite, but can detonate in confined spaces in fire. Reacts violently with strong oxidizers, acids (nitric, hydrochloric, sulfuric, picric, hydrobromic, hydrochlorous, etc.). Shock-, temperature-, and pressure-sensitive compounds are formed with antimony, chlorine, germanium compounds, halogens, heavy metals, hydrocarbons, mercury oxide, silver compounds (azides, chlorides, nitrates, oxides). Fire and/or explosions may be caused by contact with acetaldehyde, acrolein, aldehydes, alkylene oxides, amides, antimony, boron, boron halides. 

Diboron Tetrachloride. Tetrachlorodiborane(4) boron chloride. BX), mol wt 163,41, B 13,24%, Cl 86.16%, Prepd by passing gaseous boron trichloride through flow discharge between mercury or copper electrodes Urry cl al, J. Am. Client. Soc. 76, 5293 (1954) Wartik er al, If.org. Syn. 10, 118 (1967) hy passing boron trichloride vapor over boron monoxide at 200 McCloskey et aL, J, Am. Chem Soc. 93, 4750 (1961). Infrared and Raman spectra Linev-sky el al, J. Am Chem. Soc. 7S, 3287 (1953). Review of boron halides Massey, Advan. Inorg. Chem Radiockem 10, 1-152 (1967). 

As described above, the initial [Pd]—R complex can be formed by the transfer of R from another organometallic RM. Compounds of mercury, boron or tin have often been used. Alternatively an aryl, heteroaromatic or vinyl halide is added to PdL, generated in situ from PdL or by reduction of L PdX. In the second method a base such as a tertiary amine is also required to react with the hydrogen halide which is produced. 

One of the earliest methods for preparing aromatic boronic acids involved the reaction between diaryl mercury compounds and boron trichloride [198]. As organomer-curial compounds are to be avoided for safety and environmental reasons, this old method has remained unpopular. In this respect, trialkylaryl silanes and stannanes are more suitable and both can be transmetallated efficiently with a hard boron halide such as boron tribromide [199]. The apparent thermodynamic drive for this reaction is the higher stability of B-C and Si(Sn)-Br bonds of product compared to the respective B-Br and Si(Sn)-C bonds of substrates. Using this method, relatively simple arylboronic acids can be made following an aqueous acidic workup to hydrolyze the arylboron dibromide product [193]. For example, some boronic acids were synthesized more conveniently from the trimethylsilyl derivative than by a standard ortho-metallation procedure (entry 11, Table 1.3). 

The reaction of heterocyclic lithium derivatives with organic halides to form a C-C bond has been discussed in Section 3.3.3.8.2. This cannot, however, be extended to aryl, alkenyl or heteroaryl halides in which the halogen is attached to an sp2 carbon. Such cross-coupling can be successfully achieved by nickel or palladium-catalyzed reaction of the unsaturated organohalide with a suitable heterocyclic metal derivative. The metal is usually zinc, magnesium, boron or tin occasionally lithium, mercury, copper, and silicon derivatives of thiophene have also found application in such reactions. In addition to this type, the Pd-catalyzed reaction of halogenated heterocycles with suitable alkenes and alkynes, usually referred to as the Heck reaction, is also discussed in this section. 

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