Potassium naphthalene metalation

Naphthalene is known to form a stable lithium dianion at -80°C in tetrahydrofuran (THP) at concentrations lower than 0.5 mol.I-1 (9-12). Unfortunately organolithium compounds are unable to polymerize oxirane (13). Naphthalene can also be metalation by sodium and potassium in THF but no experimental evidence for a dianion of naphthalene sodium or potassium is to be found. Although naphthalene metalation by sodium is thoroughly described ( , lU, 15), very few results about potassium are published (l6, "nT As the reducing power of the alkali metals decreases from lithium (Li/Li+ = 3 02v) to potassium (K/K+ -2.92v) and finally to sodium (Na/Na+ = 2.71v) (l8), it is attractive to study in more detail the naphthalene metalation by in the THF. 

In contrast to the potassium naphthalene dianion, EN gives rise to a dianionic species at concentrations higher than 0.03 mol.l- (Table II). Furthermore the EN dianion is unable to transfer one electron to another naphthalene molecule. These sharp differences are to be attributed to the participation of the -ethyl group in the metalation process. 

Naphthalene Metalation hy Potassium in THF at Room Temperature Naphthalene Carbanions ... 

These results indicate that the naphthalene radical anion is not stable to the solvent tetrahydrofuran at room temperature on a time scale of 100 hours. Decomposition pathways are alkali metal dependent. Sodium and potassium naphthalene attack THF through a proton abstraction, cycloreversion mechanism, as previously described by Bates for the butyllithium/THF system (27). Lithium naphthalenide attacks the THF not only by the Bates mechanism but also by a nucleophilic ring opening, as is implicit in earlier high temperature work on lithium naphthalenide in THF (28) and in work on the attack of THF by tritylmagnesium bromide (29). The two smaller alkali metals, lithium and sodium, leave behind a... 

Anionic graft-polymerization of paraformaldehyde onto starch and dextrin has been effected in methyl sulfoxide solution, polymerization being initiated by the carbohydrate potassium alcoholate formed from the reaction of the carbohydrate with naphthalene potassium, a metallation procedure not previously described for carbohydrates.220... 

Other initiators based on alkali metals such as sec-butyllithium (s c-BuLi) as well as sodium and potassium naphthalene were also surveyed.Sodium and potassium naphthalene, when used as electron-transfer reagents for the initiation of styrene polymerization, react with neopentyl carbonate as a nucleophile. The investigation of oligomers obtained in the initial stages of the polymerization by means of GPC using a UV-detector revealed naphthalene to be incorporated into the growing chain. 

Ytterbium dicyclopendienide was prepared by reducing dicyclopentadienyl ytterbium chloride with finely dispersed sodium metal in tetrahydrofurane (Calderazzo et al., 1966). Samarium(II) dicyclopentadienide was isolated as the 1-tetra-hydrofuranate. This compound was prepared by reaction between SmfCsHj), and potassium naphthalene in tetrahydrofurane (Watt et al., 1969). It is insoluble in this solvent and very air-sensitive. Desolvation of the compound at elevated temperature under reduced pressure is accompanied by decomposition. 

Typical examples of initiators for cycHc carbonates-as shown for DTC-are alkali metal organic compounds such as sec-butyUithium (seoBuLi), sodium- and potassium naphthalene, and Hthium-, sodium- and potassium alkoxides or polymeric living vinyl or diene polymers with alkah metal counterions, as weU as polymeric alcoholates. The use of these macroinitiators enables the identification of side reactions, as will be shown exemplarily for polystyrene lithium (PS li ) [25]. Besides the initiation reaction of PS"Li, which represents a site transformation of... 

Tri-(l-naphthyl)phosphine is cleaved by alkali metals in THF solution. " Reaction with sodium gives the naphthalene radical-ion, with lithium the perylene radical-ion, and with potassium the radical-ion (22). Hydrocarbon radical-ion formation was thought to occur via naphthalene derived from the metal naphthalenide. E.s.r. spectra of further examples of phosphorus-substituted picrylhydrazyl radicals have been reported. ... 

When naphthalene is reduced in liquid ammonia by metallic potassium, evaporation of excess ammonia gives the solvated solid potassium naphthalide (K2 ... 

However, when the reductions were carried out with lithium and a catalytic amount of naphthalene as an electron carrier, far different results were obtained(36-39, 43-48). Using this approach a highly reactive form of finely divided nickel resulted. It should be pointed out that with the electron carrier approach the reductions can be conveniently monitored, for when the reductions are complete the solutions turn green from the buildup of lithium naphthalide. It was determined that 2.2 to 2.3 equivalents of lithium were required to reach complete reduction of Ni(+2) salts. It is also significant to point out that ESCA studies on the nickel powders produced from reductions using 2.0 equivalents of potassium showed considerable amounts of Ni(+2) on the metal surface. In contrast, little Ni(+2) was observed on the surface of the nickel powders generated by reductions using 2.3 equivalents of lithium. While it is only speculation, our interpretation of these results is that the absorption of the Ni(+2) ions on the nickel surface in effect raised the work function of the nickel and rendered it ineffective towards oxidative addition reactions. An alternative explanation is that the Ni(+2) ions were simply adsorbed on the active sites of the nickel surface. 

This is remarkable, since the reduction potential of Th(IV) to Th(III) recently has been estimated as —3.7 volts 73) and direct reduction of U(C5H5)4 and Pu(C5Hs)3 with potassium metal produces the actinide metals. The ei/z for naphthalene in acetonitrile is —2.63 V (nearly the same as the aLkaJi metals). Since this is much smaller than the Th(IV) to Th(III) reduction potential, it would seem to imply substantial stabilization of the +3 state by cyclopentadienide. The observed room temperature magnetic moment of Th(C 5115)3 (0.403 BM) is consistent with the Th(III) (5/ ) assignment. Thorium triscyclopentaxhenide is similar in behavior to U(C5H5)3, forms adducts with both THF and cyclohexyhso-nitrile and has been shown to be isostructural with the other tris (cyclopentadienyl) actinides and lanthanides. 

The H-NMR spectra of the complexes of 23 with alkali metal ions show remarkable differences. In the complex with sodium ions, the benzyl groups are in the shielding zone of the naphthalene walls, which suggests that these groups are bound in the cavity of the molecule. The potassium complex has a more open structure in which the cavity is not occupied by benzyl groups. 

Addition of an alkali metal ion to 23 should also make this host molecule a better binder of aromatic guest molecules. In the aa conformation unlike the as conformation-the 7r-electron rich naphthalene walls are capable of sandwiching rc-electron poor molecules (see Fig. 12). Indeed, upon addition of a potassium salt to a solution of 23, the for binding of 1,3-dinitrobenzene increases by a factor of 2 to 6, depending on the solvent systems [26]. Consistent with the proposed structure of the complex of 23 with sodium ions, addition of these ions has no effect on the of 23 with 1,3-dinitrobenzene. 

Naphthalene-terminated polyvinyl aromatics and polyisoprene were obtained successfully. These functional polymers were metalated by potassium in THF at 25°C. The formation of a stable dinegative ion is observed unless the naphthalene is directly attached to the end of the polyvinyl aromatics, in which case a few isoprene units can be advantageously inserted between the naphthalene end group and the polyvinyl aromatics. The polymeric and stable dinegative ion polymerizes oxirane by both anionic sites and forms three-branched starshaped block copolymers. 

Metalation of Naphthalene by Potassium in Tetrahydrofuran at Room Temperature... 

Metalation of Naphthalene Ended Polyvinyl Aromatic Chains by Potassium in THF At RT... 

Four carbonions can be formed per naphthalene end group (Figure ) whereas the naphthalene end group is completely released at the end of the metalation. This phenomenon has been thoroughly studied and will be published elsewhere (22). Briefly when naphthalene is conjugated to an aromatic nucleus the potassium dianion is unstable and the naphthalene end group is released whereas the polyvinyl anion is freed and finally isomer-ized eqs 13 to 17 summarize these observations. 

Potassium metal, which is a powerful reducing agent, reacts with naphthalene lo give potassium naphthalemde, another powerful reducing agent, which has the advantage... 

When naphthalene is reduced in liquid ammonia by metallic potassium, evaporation of excess ammonia gives the solvated solid potassium naphthalide (K2. NH3. Naphth2). If sodium is used in place of potassium, the product detonates as crystallisation starts. This is attributed to energetic expulsion of ammonia held... 

Organic substances such as methane, naphthalene, and sucrose, and inorganic substances such as iodine, sulfur trioxide, carbon dioxide, and ice are molecular solids. Salts such as sodium chloride, potassium nitrate, and magnesium sulfate have ionic bonding structures. All metal elements, such as copper, silver, and iron, have metallic bonds. Examples of covalent network solids are diamond, graphite, and silicon dioxide. 

Of this latter point, we have utilized combined GC/MS to analyze solutions of alkali metal naphthalenide in THF (90 mM metal, 40 mM naphthalene, 25 ml THF) quenched with D2O, so that we may determine the stability of the reactant system itself on a time scale of 100 hours. The predominant product, other than naphthalene itself, for both sodium and potassium naphthalenide quenches was 1-ethyl 1-protio, 4-deutero 4-protio naphthalene (3) (and/or the 1,1 2,2 isomer (4)) rather than the expected 1-deuteFo 1-protio, 4-deutero 4-protio "naphthalene (5). 

Figure 3 describes reaction schemes for naphthalene carbonization catalyzed by metallic potassium or by aluminum chloride (13,14) these catalysts produce contrasting isotropic and anisotropic carbons, respectively. The intermediate structures are similar except for more naphthenic structure induced in the AlCl -catalyzed carbonization. The role of naphthenic structures leading to optical anisotropy has been recognized in many examples, and their introduction can improve the anisotropic development, as described later. Higher fusibility, lower melting temperature, and higher solubility of the intermediate molecules may be obtained by the formation of partially naphthenic structures (15). 

Peril uorophenyl)copper (4) is most conveniently prepared by metathesis of (perfluoro-phenyl)magnesium, lithium, or cadmium reagents with copper(I) halides. Rickc and co-workers have also prepared (perfluorophcnyl)copper by the reaction of pentafluoroiodo-benzene with highly activated copper generated by the reduction of copper(I) iodide with potassium in the presence of 10% naphthalene. Utilization of normal copper metal gives rise instead to decafluorobiphenyl and no (perfluorophenyl)copper is detected. (Perfluorophenyl)-copper is a stable, isolable material which decomposes above 200 "C to form decafluorobiphenyl and copper metal, and is hydrolyzed and oxidized slowly in moist air. 

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. 

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