Preparations of metal derivatives

Methylsulphinylmethyl (dimsyl) sodium, the Corey reagent, is usually obtained from DMSO and sodium hydride under heating. The temperature range for this reaction is narrow below 70°C the process is too slow, and the anion is unstable above 85°C. Significant progress was made by Sjoberg, who sonicated the DMSO-NaH mixture at 50°C for 1 h and obtained a clear solution of the reagent, which was stable for several weeks (Eq. 77).226 

In a similar manner, an excellent preparation of potassium bis(trimethylsilyl)-amide can be achieved by sonication of potassium hydride and bis(trimethyl- 

Cerium reagents were shown to be reagents of choice in a few reactions, for instance the preparation of ketones from carboxylates, due to a high nucleophilicity and a low basicity. They are usually prepared from lithium reagents by trans-metallation with cerium chloride. The preparation of the required dry cerium chloride-THF complex was made easier when sonication was effected.228 

Zinc carboxylates are prepared in aqueous ethanol solution by sonication of zinc carbonate in the presence of the acid.1 2 Only 5-min irradiation times are required, and the method was successfully applied to Boc-protected amino acids (p. 147). Mercuric carboxylates were prepared from yellow mercuric oxide and carboxylic acids.43 The sonochemical reaction proceeds very fast in apolar solvents, and a series of salts were prepared by this method and used in hydroxy-mercuration reactions. This reaction can be effected directly from a mixture of the olefin, mercuric oxide, and a carboxylic acid (p. 119). 

Organoiron compounds were obtained easily from iron pentacarbonyl or, for a better ease of manipulation and safety reasons, from diiron nonacarbonyl. The reaction is based on Suslick s sequential metal-ligand bond cleavage. 

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Direct Combination of a 1,3-Diketone, an Amine, and a Metal Ion. Direct combination is a potentially useful reaction, and it has been used to prepare metal-salicylaldimine compounds. The procedure consists of mixing (and refluxing if necessary) a stoichiometric mixture of salicylaldehyde with an amine, a metal ion, and a base in dilute aqueous methanol. This procedure has not been applied commonly to the preparation of metal derivatives of jS-keto imines, although the preparation of 4,4 -(ethylene-dinitrilo)di-2-pentanonatocopper(II) from 2,4-pentanedi-one (acetylacetone), ethylenediamine, and copper has been described. Attempts to effect condensation of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (hexafluoroacetylacetone) and ethylenediamine by direct combination of the reactants in the presence of copper(II) acetate were imsuccessful. ... 

This procedure, a variant of method 3, is also potentially a very useful method. An advantage is that the pH of the reaction mixture is controlled by the amount of amine present. In theory, the use of this method would permit the preparation of metal derivatives of a wide variety of /8-keto imines and obviate the need for preparation and isolation of the individual ligands. In practice, it appears that of the possible compounds the most stable metal chelate compound is formed. This may not always be the desired compound. Thus, even in the presence of copper-(II) ion, the condensation of 4-imino-2-pentanone and trimethylenediamine was not successful, the product isolated being bis(4-imino-2-pentanonato)copper(II). ... 

The many satisfactory procedures which have been published for the preparation of metal derivatives of 2,4-pen-tanedione (acetylacetone) are not always successful when applied to other 8-diketones. Thus, poor yields of impure product are obtained with attempts to prepare the... 

See also Preparation of metal derivatives of 1,3-diketones, synthesis 29 Dichloro(di-2-pyridylamine)cobalt(II), synthesis 50... 

The structures, types, properties, uses, nomenclature, and general methods of preparation of metal derivatives of 1,3-diketones have been discussed in a previous volume.1 It now seems desirable to consider in somewhat more detail the various factors involved in the preparation and purification of these substances. 

Preparation of Metal Derivatives of 1,3-Diketones. Methods of preparation may be grouped into several general classes. 

Reaction of a 1,3-Diketone with a Metal Oxide, Hydroxide, Carbonate, or Basic Carbonate, a. In Aqueous Solution. The reaction between a 1,3-diketone and a suspension of a hydrous oxide or hydroxide,36 although often slow, may present the advantage of introducing minimum amounts of impurity. Furthermore, this procedure permits the preparation of metal derivatives in oxidation states that are relatively unstable under other conditions. 

Purification of Metal Derivatives of 1,3-Diketones. Despite all care in the preparation of metal derivatives, it may still be necessary to purify such compounds after they are formed. Distillation, sublimation, and crystallization (particularly the last) are the methods generally available... 

Reactivity and yields are greatly enhanced by the presence of 0.5-1% Na in the Li. The reaction is also generally available for the preparation of metal alkyls of the heavier Group 1 metals. Lithium aryls are best prepared by metal-halogen exchange using LiBu" and an aryl iodide, and transmetalation is the most convenient route to vinyl, allyl and other unsaturated derivatives ... 

If the product is to be used for the preparation of metal carbonyl derivatives, further usable material may be obtained from the mother liquors. Removal of pentane on a rotary evaporator leaves a yellow -orangc, viscous oil that is suitable for most preparative purposes. 

Alkali metal reduction is a widely employed method for the preparation of radicals derived from various classes of conjugated compounds such as hydrocarbons, heterocycles, nitro compounds, quinones, and nitriles. For... 

Transmetallation represents the most widely applicable method for the preparation of ZrCp2 derivatives. In view of the relatively low electronegativity (EN hereafter) of Zr (EN 1.2—1.4), however, transmetallation as shown in Scheme 1.9 may be expected to be favorable only with organometals containing highly electropositive metals, such as Li (EN 1.0) and Mg (EN 1.20). Indeed, facile and complete dialkylation of Cp2ZrCl2 may be readily observed with these metals. With organolithiums, however, the reaction... 

Novel thermal and metal-catalyzed di-tert-butylsilylene 161 transfer reactions have been reported by Woerpel < / /.308-312 The transfer reactions required the inital preparation of cyclohexene-derived silacyclopropanes 169-171, which has been achieved by trapping of di-fert-butylsilylenoid, generated from /-Bu2SiCl2 and lithium, with cyclohexenes (Scheme 26).305 It is noteworthy that these reactions occur with remarkably high diastereoselectivities when 2-substituted cyclohexenes are used. The silacyclopropanation of 169 with functionalized cyclopentenes under thermal conditions (115°C) has provided /razy-silacyclopropanes, such as 172, with diastereoselectivities up to 96 4, whereas no silacyclopropanes were obtained from the direct reaction of the same cyclopentenes with /-Bu2SiCl2 in the presence of lithium (Scheme 26).308... 

Hydrogen selenide is used in preparation of metal selenides and organosel-nium derivatives. It also is used in doping mix for semiconductor apphcations. 

Since the first reports23 in 1963 on metalation of imines, a number of bases such as ethyl-1 or isopropylmagnesium bromide1 24, lithium9 and potassium diethylamide13, lithium diisopropyl-amide (LDA), lithium 2,2,6,6-tetramethylpiperidide (LTMP)9 10,13, and lithium bis(trimethylsi-lyl)amide13 have been successfully applied in the preparation of imine-derived azaenolates. The most common of these reagents is LDA which has been applied in deprotonation reactions of the whole palette of different imines. 

Preparation of Ammonia Derivatives of Metallic Salts.— The principles just described will now be illustrated by directions for the preparation of some typical salts. 

The use of appropriate analytical standards is important for successful chromatographic separation, identification, and quantification of chlorophyll derivatives. While chlorophyll a and b derivatives are readily available commercially (Sigma-Aldrich) both metal-free pheophytins and metalloporphyrin analogs such as Cu2+ and Zn2+ pheophytins are not. In most instances, these derivatives must be prepared from the parent Mg-chlorophyl standards prior to use. These simple synthesis techniques are based on the work of Schwartz (1984) and are to be utilized for the rapid and efficient preparation of metal-free, Cu2+ and Zn2+ pheophytin derivatives in quantities appropriate only for analytical implementation. 

Three methods are commonly employed for the in situ preparation of organopalladium derivatives (i) direct metallation of an arene or heterocyclic compound with a palladium(II) salt (ii) exchange of the organic group from a main group organometallic to a palladium(II) compound and (iii) oxidative addition of an organic halide, triflate or aryldiazonium salt to palladium(O) or a palladium(O) complex. 

The individual dialkylamides were first applied for the synthesis of metal alkoxides by Gilman etal. who used them forthe preparation of U(OR)4 [856]. The universal character of this method was demonstarted later by Bradley and Thomas [196], who reported the synthesis of Cr(OBu )4, V(OR)4, Sn(OR)4, and Nb(OBu ) usingthis route. The advantage of this technique lies in almost quantitative yields. It also can be applied in the preparation of the derivatives of any alcohols including M(OR )n. Formation of only gaseous side products (i.e., HNR2) that can be easily removed by the evacuation can be considered to be another advantage of the technique. However, in some cases the formation of... 

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