Pentafluorophenylcopper

PENTAFLUOROPHENYLCOPPER TETRAMER, A REAGENT FOR SYNTHESIS OF FLUORINATED AROMATIC COMPOUNDS... 

If the product is isolated in a nitrogen dry box, the filtrate is evaporated without heat until a small amount of solvent remains. The precipitate is collected cold and rinsed with cold ethyl ether. The 1 1 pentafluorophenylcopper dioxane complex is obtained with no significant loss of yield and is nearly white. 

The spectral properties of pentafluorophenylcopper te-tramer are as follows infrared (Nujol) cm. 1630 medium 1391 medium 1353 medium 1275 medium 1090,1081, and 1071 strong triplet 978 strong 785 medium fluorine magnetic resonance (tetrahydrofuran with trichlorofluoromethane as internal reference) 8 (multiplicity, number of fluorines, assignment, coupling constant J in Hz.) 107.2 (20-line multiple , 2, ortho F), 153.4 (triplet of triplets, 1, para F, J= 1.3 and 20), 162.3 (17-line multiplet, 2, meta F). Absorptions at 820-900, 1100-1125, and 1290 cm.- in the infrared spectrum and at 8 3.05 in the proton magnetic resonance spectrum indicate that dioxane is still present. 

The pentafluorophenylcopper tetramer is usually analytically pure as isolated and melts at 200° with decomposition. If any significant decomposition occurs during the final drying, the product can be purified by dissolution in ether, filtration to remove copper metal, and precipitation by addition of hexane. It can also be recrystallized from benzene. When kept in a sealed container under nitrogen at room temperature, pentafluorophenyl copper tetramer appears to be stable for reasonable periods. It can be stored indefinitely at -78° under an atmosphere of carbon dioxide. 

Pentafluorophenylcopper is representative of a series of fluori-nated organocopper compounds that are highly soluble in organic solvents, more thermally stable than their hydrocarbon analogs, and useful as synthetic intermediates. " Pentafluorophenylcopper has been used to introduce the pentafluorophenyl groups and as a reagent for an improved Ullman diphenyl ether synthesis. It is... 

HPentafluorophenyOadamantane, 59, 130 (Pentafluorophenyl)benzene, 59, 127 Pentafluorophenylcopper, 59, 124 Pentfluorophenylcopper complexes, 59, 127 PENTAFLUOROPHENYLCOPPER TETRAMER, 59,122 2-(Pentafluorophenyl)ethylamine hydrochloride, 57, 82... 

Pentafluorophenylcopper is first isolated as a 1 1 complex with dioxane which is usually white. Half of the complexed dioxane is very labile and is usually lost during vacuum drying, giving the 2 1 complex. Excessive heating can cause loss of additional dioxane (lower apparent yield) and eventually decomposition of the product. 

Pentafluorophenylcopper exists as a tetramer. It forms complexes with a variety of reagents and solvents as well as ate complexes a representative list is given in Table I. For many syntheses the crude reaction mixtures of cuprous halide with either pentafluorophenylmagnesium bromide, or pentafluorophenyllithi-um, or the pentafluorophenylcopper-dioxane complex react as well as the solvent-free tetramer. 

A. (Pentafluorophenyl)benzene. A 100-ml., round-bottomed flask equipped with a magnetic stirring bar and a reflux condenser bearing a nitrogen inlet is flushed with nitrogen. The flask is charged with a solution of 2.40 g. (0.0026 mole) of pentafluorophenylcopper tetramer in 25 ml. of benzene, and 2.12 g. 

Pentafluorophenylcopper tetramer Copper, tetrakis(pentafluoro-phenyl)tetra- (8,9) (34077-61-7)... 

Pentafluorophenylcopper was prepared by the metathesis of pentafluorophenyl magnesium, pentafluorophenyllithium or pentafluorophenylcadmium reagents... 

Pentafluorophenylcopper exhibits high reactivity towards a variety of organic substrates such as aryl, vinyl, alkynyl, allyl halides etc. [226,227,229,235-238] (Scheme 77). Similar to trifluorovinylcopper, pentafluorophenylcopper readily adds to hexafluoro-2-butyne to form the syn addition product, which can be quenched with electrophiles [230] (Scheme 78). 

Recently, a unique double difluoromethylene insertion into the carbon-copper bond of pentafluorophenylcopper has been reported [239]. Pentafluoro-phenylcopper reacted with trifluoromethylcopper in DMF at -30 °C to room temperature to form perfluoro-2-phenylethylcopper (C6F5CF2CF2Cu) in high yield, which readily underwent a variety of functionalization reactions with electrophiles [239] (Scheme 79). 

Two other exchange reactions have been reported cyclopentadienyl-thallium and pentafluorophenylsilver react with a copper(I) halide to give cyclopentadienylcopper complexes (86) and pentafluorophenylcopper (203), respectively. 

The formation of transient organocopper compounds has been inferred in many decarboxylations of copper(I) carboxylates or copper-carboxylic acid systems 20, 33, 47, 56, 211, 213, 215, 279). Only one copper compound has been isolated, so far. Tbe decarboxylation of copper(I) pentafluorobenzoate in quinoline proceeds smoothly at 60°C to give a pentafluorophenylcopper-quinoline complex 33, cf. 254). 

Trifluoromethyl)phenylcopper was found to be an octamer by consideration of the kinetics of its decomposition, and by cryoscopy and vapor pressure osmometry in benzene solution 36). Its F NMR spectrum in ether at room temperature is a sharp singlet. Consequently, the suggested structure is a central copper cube with equivalent bridging benzotri-fluoride groups. The initial decomposition product, Cu8( n-CF3CgH4)e, is considered to be a Cu(0)—Cu(I) octanuclear cluster compound 36). For the octameric m-(trifluoromethyl)phenylcopper, the tetrameric ortho isomer, and pentafluorophenylcopper tetramer, the F NMR spectra were found to vary with temperature. The changes are not considered to involve important structural alterations, but only variations in solvent complexes and rotamer populations 32, 37). The spectra also... 

Pentafluorophenylcopper tetramer is reported to form complexes with the 7T-bases 2-butyne and 1,5-cyclooctadiene (52). 

Perfluoroalkylcopper and perfluoroarylcopper compounds are noticeably more thermally stable than the corresponding alkyl and aryl compounds. Solutions of perfluoroalkylcopper compounds in DMSO or DMF are stable up to at least 120°C 200), whereas ether suspensions of alkylcopper compounds decompose at 0°C or below. Similarly, pure pentafluorophenylcopper tetramer decomposes at 210°C-220°C, and a sample has been kept in a Dry Ice chest for 5 years 32). However pure phenylcopper can be kept for no more than a few days, even under nitrogen 73). Solutions of pentafluorophenylcopper reagents containing metal halides in THF have been refluxed for 5 days or more without decomposition (97, 144). Other stable perhaloarylcopper reagents are those in which the aryl moiety is perfluoro(p-phenoxyphenyl) (96), pentachlorophenyl, and 2,3,5,6-tetrachloropyridyl 144), none of which... 

Organocopper compounds can form mixed aggregates. For example, a mixture of pentafluorophenylcopper and o-(trifluoromethyl)phenyl-copper tetramers forms mixed cluster compounds in which ligands have been exchanged. The products may be explained by either a cluster... 

A slightly different mechanism has been proposed by Cairncross and Sheppard (37) for the reaction of fluoroarylcopper compounds with substituted alkyl halides. Pentafluorophenylcopper can form a complex with bicyclooctyl bromide by coordination with the halogen atom. Such a complex may go directly to coupled product in a four-center process, or, depending on the nature of the group attached and the nature of the alkyl moiety, may form an ion pair which collapses to the coupled... 

Coupling between a pentafluorophenylcopper reagent and an alkyl halide is not a recommended route to the alkylpentafluorobenzenes if the alkyllithium reagent is available 147). 

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