Pentafluorophenyl lithium

The borohydride reactions (148) with [C5HjFe(CO)3 j.(CNCH3),(]PF4 (x = 2,3) have been noted above, as have the reactions of pentafluorophenyl-lithium with these species (x = 1, 2, 3) 143, 146). 

The organolithium-reagent (5) is itself capable of forming the aryne (9) which can add pentafluorophenyl-lithium. This was found to occur and gave the terphenyl derivatives (10) and (11) in the ratio of 1 9 26>. 

When we allowed pentafluorophenyl-lithium to decompose in ether in the presence of an excess of N, ZV-dimethy laniline we obtained the compounds (92) 70, X = F), (94), the latter as the major compound, and a product which was shown to be (97). That this latter compound did not arise by metallation of 2V,lV-dimethylaniline followed by addition to tetrafluorobenzyne was shown by quenching the reaction mixture with deuterium oxide. No deuterium incorporation was detected. The compound (97) provides a rare example of a product derived by a Stevens rearrangement in which aryl migration has occurred b>. 

When we carried out a reaction in which we allowed a solution of pentafluorophenyl-lithium in light-petroleum to decompose in the presence of Af.AT-dimethylaniline we obtained a fifth product. This compound was an extremely weak base and was shown to be (98). Presumably the... 

Decafluorodibenzoyl reacts with pentafluorophenyl lithium to give 4,5,6,7-tetrafluoro-2,2-bis(pentafluorophenyl)benzofuran-3(2//)-one (9).138... 

The reaction of tellurium tetrachloride (9.3 mmol) with pentafluorophenyl lithium (24 mmol) in diethyl ether/hexane solution gave lris pentafluorophenyl] telluronium chloride (m.p. 188-1900)5. 

In addition to these cycloaddition reactions with nucleophilic Tr-donors, tetrafluoro-benzyne is very susceptible to more general nucleophilic attack. Biphenyl derivatives often occur as by-products in reactions of pentafluorophenyl-lithium, formed by addition to the benzyne [204, 229] (Figure 9.89). 

Tris(pentafluorophenyl)aluminium is obtained as the etherate from either the Grignard reagent in ether or the lithium derivative in ether/hexane [81, 85], whereas only complex materials are obtained from pentafluorophenyl-lithium in hexane (Figure 10.34). Attempts to remove the ether from the etherate, 10.34A, inevitably led to explosions. 

Reactions of tellurium tetrachloride with methyl lithium or pentafluorophenyl lithium yielded triorgano telluronium halides. 

Z = F Y = F, Z = Me). Decafluoro-l,4-dihydronaphtha] ie also reacts with piperidine, sodium methoxide, hydrazine, ammonia, and pentafluorophenyl lithium at the 6-position, and the 1,2-dihydronaphthaIene gives the 6- and 7-mono-substituted products wdth the first two of these reagents. ... 

The reaction of bispentafluorophenyl sulphide with trifluoromethyl hypofluorite (see p. 284) affords the sulphurane (CeF5)2SF2, which may apparently also be obtained from pentafluorophenyl-lithium and sulphur tetrafluoride (c/. Vol. 2, p. 438) 5 the n.m.r. spectrum of the sulphurane at — 80 °C indicates that the ortho-fluorine atoms are inequivalent. 

The known l-cfaloro-2-pentafiuorophenylacetylene has been isolated from reactions between pentafluorophenyl-lithium and the olefins CHChCFj and CX)IF CC1F. The reactions appear to proceed by elimination of lithium fluoride from intermediate alkenyl-lithiums, themselves formed by a nucleophilic addition-elimination-metallation sequence, e.g. Scheme 46. Attempts... 

Olefinic Compounds and Related Polymers.— The synthesis and polymmiz-ation of fluorinated styrenes and phenyl vinyl ethers has been reviewed." Patent claims for the preparation of octafluorostyrmie (see Vol. 1, p. 200) have been extended to cover old work on the dehydrochlorination of (2-cMofo-l,2,2>trifluoroethyl)pentailuorobenzene with molten potassium hydroxide or with carbon pellets impregnated with potassium hydroxide. Reasonable yields of the styrene can be obtained by these methods, but the route from readily available materials is long, and a more convenient laboratory preparation involves the reaction of pentafluorophenylcopper with trifluoro-iodoethylene (55 % yield). The reaction of pentafluorophenyl-lithium with an excess of tetrafluoroethylene in ether at -20 °C also gives octafiuoro-... 

Kinetic studies of the gas-phase pyrolysis of 1-aiylethyl acetates (ArCHMe-O COMe Ar = Ph or CeF ) have established that, at 625 K, pentafluoro-styrene is formed 4.60 times more slowly than styrene undo identical conditions. Previous results with monofluoro-compounds show that, if the effects of the fluorine atoms were additive, a retardation factor of 7.75 woidd be obsraved, and it is suggested that the five fluorine atoms are acting to some extent in opposition and that the full —I effect of each cannot be exerted. " Similar conclusions have been reached as a result of studies of the u.v. spectrum of 2,3,4,5,6-pentafluoro-Malachite Green (64) (synthesized via the reaction of pentafluorophenyl-lithium with Michler s ketone), which shows a bathochromic shift of only 37 nm in the A -band with respect to the unfluorinated analogue. ... 

Vanadium.— Reaction of pentafluorophenyl-lithium with vanadium tetrachloride in diethyl ether and hexane at — 70 °C yields tetrakis(pentafluoro-phenyl)vanadium, which crystallizes as the dietherate at 0 °C. It is very moisture sensitive, yielding pentafluorobenzene and a trace of perfluoro-biphenyl, and with mercuric chloride in tetrahydrofuran yields bis(penta-fluorophenyl)mercury (95%). 

Reaction of pentafluorophenyl-lithium with tungsten pentachloride in diethyl ether yields the bright-green complex LiW(C,F5)5,2Et,0, which is stable for several months at -10 °C, and decomposes only slowly at room temperature. It yields (C F5)2Hg with mercuric chloride, CeFsI with iodine, and is hydrolysed to pentafluorobenzene. When heated to 100 °C it gives pentakis(pentafluorophenyl)tungsten as an orange-red solid in low yield and a tungsten(iv) derivative, (C,F5)iW, may be formed, but is too unstable to isolate. ... 

Reaction of pentafluorophenyl-lithium with the ruthenium complex [(7T-CjHj)Ru(PPh2)2CI] in n-hexane at —78 °C to room temperature yields the o--complex [(7r-CjH,)Ru(PPha)2C,F5). ... 

The equilibria implied in the nucleophilic mechanism are firmly grounded in experiment. The ate complex 12 formed in the reaction of phenyllithium with iodobenzene has been characterized at low temperature, and that from (pentafluorophenyl)lithium and iodopentafluorobenzene, 13, has been isolated and characterized by X-ray crystallography. ... 

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