Mercury alkyl halides, 66 complexes

Whereas Al alkyls and alkyl halides are completely hydrolyzed in water, dialkyl compounds of Ga, In, and Tl give well-characterized compounds in aqueous solution. Thallium gives very stable ionic derivatives of the type R2T1X (X = halide, SO4-, CN , NO3, etc.) which resemble the isoelectronic mercury dialkyls R2Hg in being unaffected by air and water. The [TlMe2]+ ion is linear, but does not form an aquo complex like Me2Ga(H20)2. 

Vanhoye and coworkers [402] synthesized aldehydes by using the electrogenerated radical anion of iron pentacarbonyl to reduce iodoethane and benzyl bromide in the presence of carbon monoxide. Esters can be prepared catalytically from alkyl halides and alcohols in the presence of iron pentacarbonyl [403]. Yoshida and coworkers reduced mixtures of organic halides and iron pentacarbonyl and then introduced an electrophile to obtain carbonyl compounds [404] and converted alkyl halides into aldehydes by using iron pentacarbonyl as a catalyst [405,406]. Finally, a review by Torii [407] provides references to additional papers that deal with catalytic processes involving complexes of nickel, cobalt, iron, palladium, rhodium, platinum, chromium, molybdenum, tungsten, manganese, rhenium, tin, lead, zinc, mercury, and titanium. 

The cyclopentadienyltin compounds (and cyclopentadienyl derivatives of other metals such as mercury and lead) are very sensitive to photolysis, and on irradiation with UV light in an ESR spectrometer they show the spectrum of the cyclopentadienyl radical the stannyl radical is difficult to observe directly under these conditions, but its presence is established by the reactions which it shows with substrates such as alkyl halides. This provides a useful route to a variety of stannyl radicals (see Section 20.1.1), and a method of generating cyclopentadienyl radicals for study by ESR spectroscopy.125 It would be interesting to extend these ESR studies to the more complex compounds 9-6-9-9, which are known to be photosensitive. 

Ketene dithioacetals are deprotonated with LDA-HMPA and complexed with copper(l) iodide (Scheme 36). This reagent reacts with allylic halides exclusively at the y-position with allylic rearrangement (5n20. The reaction of the lithium reagent with simple alkylating reagents gives mostly a-attack. Ketene dithioacetals can be converted to esters by aqueous mercury(II) chloride. 

Halides of zinc, cadmium, and mercury are readily alkylated by aluminum alkyls (117, 303). All of the alkyl groups of the aluminum participate in the reaction with HgCl2. But the alkylation does not proceed beyond the formation of alkyl mercury chlorides, RHgCl, except in the presence of a complexing agent (e.g., NaCl). Then complete alkylation to the mercury dialkyl occurs. 

Vinyl complexes are typically prepared by the same methods used to prepare aryl complexes. Vinyl mercury compounds, like aryl mercury compoimds, are easily prepared (by the mercuration of acetylenes), and are therefore useful for the preparation of vinyl transition metal complexes by transmetallation. The use of vinyl lithium reagents has permitted the s rnthesis of homoleptic vinyl complexes by transmetallation (Equation 3.35). Reactive low-valent transition metal complexes also form vinyl complexes by the oxidative addition of vinyl halides with retention of stereochemistry about the double bond (Equation 3.36). Vinyl complexes have also been formed by the insertion of alkynes into transition metal hydride bonds (Equation 3.37), by sequential electrophilic and nucleophilic addition to alkynyl ligands (Equation 3.38), and by the addition of nucleophiles to alkyne complexes (Equation 3.39). The insertion of alkynes into transition metal alkyl complexes is presented in Chapter 9 and, when rearrangements are slower than insertion, occurs by s)m addition. In contrast, nucleophilic attack on coordinated alkynes, presented in Chapter 11, generates products from anti addition. 

Mercury compounds 66,305,313 Metal alkene compounds 76, 304 Metal alkyl compounds 66, 296, 302 Metal alkyne compounds 84, 307 Metal ammine complexes 296. 309 Metal aryl compounds 158 Metal azides 92, 295. 321 Metal carbonyl compounds 121, 294, 295, 309, 314, 317 Metal cyano compounds 297, 303 Metal ethylene complexes 73, 296, 304 Metal halides 297, 303 Metal hexafluoro compounds 304 Metal hydrides 293, 323 Metal-ligand vibrations 292 Metal olefin compounds 73, 76, 296, 304... 

A new type of catalyst, a cobalt carbonyl complex, has been found for low-temperature (viz. 50 °C) homogeneous hydroformylation of alkenes. Nafion-H (a superacidic perfluorinated resin sulphonic acid) impregnated with mercury is recommended as a catalyst for the hydration of alkynes R C=CR (R = H or aryl, R = H, alkyl, or aryl) to form ketones R CH2C0R. Two mild methods for the hydrolysis of vinyl halides to ketones have been described one utilizes Bp3,Et20 and mercury(ii) acetate in acetic acid and the second mercury(ii) acetate in trifluoroacetic acid/ ... 

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