Naphthalene complexe

The addition product, C QHgNa, called naphthalenesodium or sodium naphthalene complex, may be regarded as a resonance hybrid. The ether is more than just a solvent that promotes the reaction. StabiUty of the complex depends on the presence of the ether, and sodium can be Hberated by evaporating the ether or by dilution using an indifferent solvent, such as ethyl ether. A number of ether-type solvents are effective in complex preparation, such as methyl ethyl ether, ethylene glycol dimethyl ether, dioxane, and THF. Trimethyl amine also promotes complex formation. This reaction proceeds with all alkah metals. Other aromatic compounds, eg, diphenyl, anthracene, and phenanthrene, also form sodium complexes (16,20). 

Carbanions ia the form of phenyllithium, sodium naphthalene complex, sodium acetyHde, or aromatic Grignard reagents react with alkyl sulfates to give a C-alkyl product (30—33). Grignard reagents require two moles of dimethyl sulfate for complete reaction. 

Complexation with polyaromatic systems has also been observed. For instance, Mlnaphthalenelj, M = Cr (88,183), Mo (183), V (183), or Ti (183) may be synthesized in a solution reactor with the appropriate, metal vapors at liquid-nitrogen temperature. The Cr/naphthalene complex is less stable (dec. 160°C) than CrtCsH ) (m.p. 283-284° C). In fact, the naphthalene ligand is sufficiently labile to allow reaction under mild conditions, to afford CrL (L = CO or Bu NC), or Cr(naphth)Ls [L = PFj, P(OMe)3, or PMea]. The Mo, V, and Ti species are equally reactive. Analogous 1-methylnaphthalene complexes were also isolated (183). In addition, the complexes shown in Fig. 38 were synthesized by reaction, at the temperature of liquid nitrogen, of Cr atoms with 1,4-diphenylbutane (35, 201, 202). Analogous complexes were formed with 1,5-diphenylbutane (202). 

Sodium naphthalene, 74 247 Sodium naphthalene complex, 22 764 Sodium niobate, 77 153 Sodium nitrate, 22 843-853, 860-862 applications of, 22 843, 852-853 commercial grades of, 22 850t crystallization of, 22 848 deposits of, 22 843-845 described, 22 843 economic aspects of, 22 849... 

When larvae were exposed to an equivalent concentration of radio-labeled naphthalene complexed with bovine serum albumin (BSA), the maximum value for accumulated metabolites was 21%. Radio-labeled naphthalene was almost entirely depurated in 24-36 hr, whereas metabolic products were strongly resistant to depuration... 

Figure 4. Accumulation of naphthalene and metabolic products (expressed as naphthol) after exposure of stage V spot shrimp to 8-12 ppb of waterborne [1-14C] naphthalene and [1- 4C]naphthalene complexed with BSA (A), regression lines of concentrations of [l-,4C]naphthalene with sampling points indicated (B), median values of metabolic products with data ranges (47).

An alternative mechanism for the formation of a two hosts-two guests complex has been suggested. From equilibrium studies of the concentration-dependence of the absorption spectra and excimer fluorescence intensities of naphthalene in the presence of beta cyclodextrin, Hamai ° concluded that the excimer fluorescence is due to a two hosts-two guests complex, formed by the association of two 1 1 beta cyclodextrin-naphthalene complexes. Thus, the mechanism can be described as follows. 

Reduction is defined as acceptance of electrons. Electrons can be supplied by an electrode - cathode - or else by dissolving metals. If a metal goes into solution it forms a cation and gives away electrons. A compound to be reduced, e.g. a ketone, accepts one electron and changes to a radical anion A. Such a radical anion may exist when stabilized by resonance, as in sodium-naphthalene complexes with some ethers [122], In the absence of protons the radical anion may accept another electron and form a dianion B. Such a process is not easy since it requires an encounter of two negative species, an electron and a radical anion, and the two negative sites are close together. It takes place only with compounds which can stabilize the radical anion and the dianion by resonance. 

The spectra from the NDO-naphthalene complex also revealed a second binding conformation (denoted as B), in which the substrate is located -0.5 A from the Fe atom. (From Yang et ah, 2003)... 

Perutz and coworkers [180] have used 2D EXSY to study the dynamic behavior of RhCp(PMe3)(q -naphthalene), 109, which is thought to be a model intermediate for the oxidative addition of arenes to a metal center. In this complex, there are two processes taking place. The first involves an equilibrium between the -naphthalene complex, 109, and the naphthyl hydride complex, 110. The second process involves an intramolecular [l,3]-shift which moves the coordination site of the naphthalene ring from one side of the ring to the other (Scheme 1.12). 

Koton, et al. (7 8) have studied the acrolein propagation initiated by Na-Naphthalene complex or by t-butyllithium in tetrahydrofuran (THF) at various temperatures. From these results, a mechanism has been deduced, but it ignores the transfer reactions and the different complexations of the living end. 

In this article, we have summarized the main results of our kinetic study (particularly transfer and propagation rate constants) obtained in THF with Li+ and Na+ Naphthalene complex as initiators. We have also given the microstructure of polyacroleins obtained with the same initiators. 

Funt et al. followed this work and have extended it in detail. When naphthalene was added to the tetrahydrofuran solution of NaAl(CaH6)4 and NaB(C6H8)4 without monomer, they found the green sodium naphthalene complex produced by electrolysis (11). Upon the addition of styrene monomer, generation of the orange living polystyryl anions was spectrophotometrically observed. 

Chart 6 2-[(dimethylamino)methyl]naphthalene complexes of pzTpPd... 

Although there are few five-membered metallacycles reported for group 5, there are some examples of metallacyclopentane compounds for niobium and tantalum. The reaction of the labile vanadium naphthalene complex [CpV(Ci0H8)] with ethene provided the unusual binuclear complex [Cp2V2(p-C4H8)2] (34 [Eq. (13)], Fig. 9) in which the two vanadium centres are bridged by two butanediyl groups.38... 

The naphthalene complex of [Os] (3) reacts with triflic acid to form a /3-lH-naphthalenium species, which has been characterized at —40 °C [16]. Unfortunately, most nucleophiles react as bases with this species and return the naphthalene complex. However, MMTP and the mild hydride donor triethylsilane (Table 4, entries 1 and 2) both add to C4 of the complex and yield 1,4-dihydronaphthalenes in moderate overall yield following decomplexation [17]. 

As mentioned in the introduction, one of the major advantages of using transition metals for dearomatization is that they allow the isolation of reaction intermediates and, consequently, broaden the range of accessible manipulations. For example, when the naphthalene complex of [Os] (3) is treated with dimethoxymethane in the presence of HOTf, the resulting 3-lH-naphthalenium species 23 can be isolated in 88 % yield and stored for days at room temperature (Table 5). The electrophile adds anti to the face involved in metal coordination and pushes the proton at Cl toward the metal, which prevents spontaneous rear-omatization. As shown in Table 5, 23 reacts with MMTP, the conjugate base of dimethyl malonate, 2-trimethylsiloxypropene, tetrabutylammonium cyanoborohydride (TBAC), dime-... 

In solution, naphthalene complexes of the form TpRe(CO)(L)( /2-naphthalene) exist as mixtures of diastereomers A and B (Table 15). Only when L = PMe3 (entry 1) does the unbound ring of the naphthalene show a thermodynamic preference for quadrant a (98A). For all... 

Szwarc (65, 67) first studied the system sodium-naphthalene-styrene in tetrahydrofuran at 0 to — 78°. After adding styrene the green color of the sodium-naphthalene complex gave way to the red color of the styryl carbanion. At 100% conversion the UP was found to be... 

Materials. Tetrahydrofuran. The monomer was refluxed over potassium until a small amount of distillate easily developed the green sodium naphthalene complex. It was then distilled from potassium under nitrogen, and a center cut was stored in vacuo in the presence of a sodium naphthalene complex. When needed, the monomer was distilled under high vacuum from the storage vessel into breakseals and weighed. 

The first tris(arene)niobinm complex, [Nb(l-4-J7 -anthracene)3], prepared by the Na or K anthracene rednction of NbCL (THF)2, undergoes facile anthracene displacement in the presence of CO to afford [K(18-crown-6)(THF)2][Nb(CO)6]. Rednction of TaCls by sodinm naphthalene provides [Na(THF)][Ta(j7 -naphthalene)3], the first homoleptic naphthalene complex of a third row transition metal. This complex reacts with CO and anthracene to give [Ta(CO)6] and [Ta(l-4-jj -anthracene)3], respectively. The latter prodnct reacts with cyclooctatetraene (COT) to give [Ta(COT)3]... 

Another route to bis( -arene)vanadium(0) compounds is the cocondensation of arenes with vaporized vanadium metal (see Metal Vapor Synthesis of Transition Metal Compounds) On treatment with 1,3-cyclohexadiene and butyllithium, 15-electron vanadocene (5) is converted to 16-electron ( -benzene)( -cyclopentadienyl)vanadium(l) (6) (Scheme 3). Use of potassium naphthalenide affords the corresponding naphthalene complex. 

They may be prepared by heating Cr(CO)g or Cr(CO)3(NH3)3 in the arene as solvent (Scheme 10.27) or, when use of excess arene is undesirable, by exchange with the naphthalene complex 10. The procedure works well for electron-rich arenes, but is of no value for electron-deficient aromatic compounds. Decomplexation can subsequently be... 

Alkali metal naphthalene complexes have also been used to initiate epoxide polymerizations. Solov yanov and Kazanski [25] studied the polymerization of EO in tetrahydrofuran using sodium, potassium or cesium naphthalene as initiator. A living polymer was produced there is no chain rupture or transfer. The rate of polymerization depends on the concentration of active centres in a complex manner. The kinetic order varies from 0.23 for Na" (or 0.33 for K and Cs" ) up to full first order as initiator concentration decreases. The polymerization is first order in monomer, but deviations are observed at high concentrations. 

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