1.2- dimethoxyethane , organometallics

Widely used starting materials, particularly in organometallic chemistry, are the solvated halide (Cl, Br, I) complexes such as CrCl3(THF)3 or RhCl3(THT)3 or similar acetonitrile complexes these are usually more reactive then anhydrous metal halides in organic solvents such as tetrahydrofuran, 1,2-dimethoxyethane, and other ethers unless the halides are soluble. 

Protection or reductive deoxygenation of alcohols and ketones. Ireland et al.2 have found that N,N,N, N -tetramethylphosphoroiiamidates (TMPDA derivatives) of alcohols and of ketone enolates are reduced in high yield by lithium-ethylamine. They are readily prepared by phosphorylation of alcoholate or enolate anions. The complete sequence is as follows. The alcoholate anion is simply prepared by treatment of an alcohol with a slight molar excess of n-butyllitliium. The enolate anions of saturated ketones are prepared by treatment with lithium diisopropylamide. In the case of a,/J-unsaturated ketones, lithium-ammonia reduction or conjugate organometallic addition is suitable. For phosphorylation of the Jnion a fivefold excess of N,N,N, N -tetramethyldiamidophosphorochloridate in 4 ] dimethoxyethane (or THF)-N,N,-N. N -tetramethylethylenediamine (TMEDA) is used. The reaction is complete after... 

Similar to group-II metal organyls, the reaction is complete with the association of the organometallics. In donor solvents [ether, dimethoxyethane (glyme), etc.] the associates break down to form more definite ionic species, and there is a rapid equilibrium between intimate and solvent-separated ion pairs. 

Similarly, in reaction 18.3, the acidic CH2 group in cyclopen-tadiene can be deprotonated to prepare the cyclopentadienyl ligand which is synthetically important in organometallic chemistry (see also Chapter 23) Na[Cp] can also be made by direct reaction of Na with C5H5. Na[Cp] is pyrophoric in air, but its air-sensitivity can be lessened by complexing the Na+ ion with 1,2-dimethoxyethane (dme). In the solid state, [Na(dme)][Cp] is polymeric (Figure 18.1). 

Dimethyl Cellosolvey monoglyme or 1 2 dimethoxyethane (DME) is an odourless liquid boiling at 85 C. Its dielectric constant is 12 and its dipole moment 1.71 D, It thus resembles tetrahydrofuran in most of its properties. It is a good solvent for the alkali metals with which it forms blue conducting solutions. It also dissolves organometallics. ... 

Polar solvents such as ethers and amines react with organometallic initiators, as well as propagating polystyryl and polydienyl carbanions, to decrease the concentration of active centers (21-23). The rate of reaction with ethers decreases in the order Li > Na > K. For example, dilute solutions of poly(styryl)lithium in tetrahydrofuran (THF) at room temperature decompose at the rate of a few percent each minute. Alkyllithium initiators also react relatively rapidly with ethers the order of reactivity of organolithium compoimds with ethers is tertiary RLi > secondary RLi > primary RLi > phenyllithium > methyllithium > benzyllithium (21). An approximate order of reactivity of ethers toward alkylithium compounds is dimethoxyethane, THF > tetrahydropyran> diethyl ether> diisopropyl ether. Tertiary amines can also react with alkyllithium compoimds. The importance of these reactions can be minimized by working at lower temperatures (eg, <0°C) it is also advisable to use only the minimum amounts of ethers and other Lewis bases required as additives. 

Since 1972, we have published many reports describing convenient methods for the generation of highly reactive metal powders and their use in organic as well as organometallic synthesis [28-34]. Most of the active metals prepared by our group have been prepared in ethereal solvents [35]. Our initial report on the preparation of active uranium (I) employed 1,2-dimethoxyethane (DME) as a solvent (Scheme 13.1) [31]. We have since developed a method for preparing active uranium (3) in hydrocarbon solvents, which leads to a much cleaner and more controllable chemistry compared to 1 [34, 36]. 

Although CP2MX2 compounds are a cornerstone of early transition-metal organometallic chemistry, such species are rather unstable for the actinides. Thus, CP2UCI2 prepared in 1,2-dimethoxyethane (DME) via the route below ... 

Sublimation of the products provides the pure trichlorides, which have very low solubility in organic solvents, constituting a problem for use in metathesis syntheses of organometallic and related compounds. More soluble [LnCl3(solv)J (solv=tetrahydrofiiran (thQ or 1,2-dimethoxyethane (dme)) complexes are prepared by oxidation of the metals with hexachloroethane. ... 

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