Electron structure and reactivity of organofluorine compounds. 4. AMI calculations of anion radicals of primary,secondary, and tertiary perfluoroalkyl chlorides,bromides, and iodides

Calculations were carried out using the semiempirical quantum chemical AMI method for anion radicals (AR) of the perfluoroalkyl halides (R_FX): CF₃X, CF₃CF₂X, (CF₃)₂-CFX, and (CF₃)₃CX for X=Cl, Br, and I. All the AR's studied are thermally stable. The electron affinity of the perfluoroalkyl halides, and consequently, the thermal stability of their AR's increases in the series from F-methyl to F-tertbutyl halides and from the chlorides to bromides and iodides. During formation of an AR the spin density is preferentially localized on the * orbital of the C–X bond which leads to an increase in the distance between these atoms. Dissociation of the AR of tert-perfluorobutyl iodide to a perfluorocarbanion and an I atom is thermodynamically more favorable than dissociation with formation of a perfluoroalkyl radical and I^–.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1064–1068, May, 1990.     

Polar addition of perfluoro-tert-hexyl iodide to alkenes and alkynes

The effective charges on the atoms in molecules of perfluoroalkyl halides of general formula (CF₃)_nCF_3–nX (X=Cl, Br, I) have been calculated by the AM1 semiempirical method. In polar solvents perfluoro-tert-hexyl iodide is reduced under the action of alkenes and aromatic hydrocarbons to form 2-hydroperfluoro-2-methyl-pentane and perfluoro-2-methyl-2-pentene. In ethyl acetate the regio- and stereo-specific addition of perfluoro-tert-hexyl iodide to alkenes, butadiene, and alkynes takes place, which is associated with the realization of a polar ion-radical mechanism for the reaction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2057–2061, September, 1989.     

Photoelektronen-Spektren und Moleküleigenschaften. 132 [1, 2]. Trifluormethylsulfan und Derivate F3CSX (X  CF3, Cl,Br, I)

Photoelectron Spectra and Molecular Properties. 132. Trifluoromethylsulfane and Derivatives F₃CSX (X ? CF₃, Cl, Br, I) The He(I) photoelectron spectra of trifluoromethylsulfane F₃CSH and its derivatives F₃CSX (X ? CF₃, Cl, Br, I) are assigned by Koopmans' correlations, IE = ?ε, with MNDO eigenvalues, by radical cation state comparison and based on resolved vibrational fine structures, which can' be discussed by MNDO FORCE calculations. The spin/orbit splitting in F₃CSI can be approximated by additional ITEREX-85 calculations. Gasphase thermolysis of the trifluoromethylhalogensulfanes F₃CSX at 10^?4 mbar yields decomposition temperatures, which decrease from X ? Cl to I, and as fragmentation products of presumably radical intermediates, in addition to the respective halogens X₂ and F₂C?S, also F₃CX as well as S₂ and CS₂ (X ?Cl, Br) are PE spectroscopically detected.     

Mass spectra of perfluoroalkyl and perfluoroalkylether nitriles and acyl halides

Electron impact fragmentation patterns were obtained for perfluoroalkylether nitriles, C,F,O[CF(CF₃)CFIO]ICF(CF₃)CN (x = 1 and 2), perfluoroalkylether acyl halides, CSF,OCF(CF,)-CF₂OCF(CF₃)COX (X = F and Cl), n-perfluorooctanonitrile and n-perfiuorooctanoyl chloride. The perfluoroalkyl and perfluoroalkylether nitriles afforded ions characteristic of the nitrile function. The major fragment from the acyl chlorides was the [COClJ]+ ion; the presence of chlorine was evidenced also by rearrangement ions of the general form [R_fCl] t. The perfluoroalkylether compounds appeared to undergo a typical fragmentation governed by the cleavage of the carbon-oxygen bond.     

Tris(trifluoromethyl)borane Adducts of Cyanogen Halides

The reactivity of carbonyl‐tris(trifluoromethyl)borane (CF₃)₃BCO against the homologous series of cyanogen (pseudo)halides NCX, X = F, Cl, Br, I, CN, was investigated. Lewis acid‐base adducts (CF₃)₃BNCX were obtained for X = Cl, Br, I, CN and were characterized by vibrational and NMR spectroscopy. It appeared that FCN did not react and twofold complexation of NCCN does not occur, in agreement with theoretical complexation energies and QTAIM charges.     

Magnitude and origin of the attraction and directionality of the halogen bonds of the complexes of C6F5X and C6H5X (X = I, Br, Cl and F) with pyridine

The geometries and interaction energies of complexes of pyridine with C₆F₅X, C₆H₅X (X=I, Br, Cl, F and H) and R_FI (R_F=CF₃, C₂F₅ and C₃F₇) have been studied by ab initio molecular orbital calculations. The CCSD(T) interaction energies (E_int) for the C₆F₅X–pyridine (X=I, Br, Cl, F and H) complexes at the basis set limit were estimated to be ?5.59, ?4.06, ?2.78, ?0.19 and ?4.37 kcal mol^?1, respectively, whereas the E_int values for the C₆H₅X–pyridine (X=I, Br, Cl and H) complexes were estimated to be ?3.27, ?2.17, ?1.23 and ?1.78 kcal mol^?1, respectively. Electrostatic interactions are the cause of the halogen dependence of the interaction energies and the enhancement of the attraction by the fluorine atoms in C₆F₅X. The values of E_int estimated for the R_FI–pyridine (R_F=CF₃, C₂F₅ and C₃F₇) complexes (?5.14, ?5.38 and ?5.44 kcal mol^?1, respectively) are close to that for the C₆F₅I–pyridine complex. Electrostatic interactions are the major source of the attraction in the strong halogen bond although induction and dispersion interactions also contribute to the attraction. Short‐range (charge‐transfer) interactions do not contribute significantly to the attraction. The magnitude of the directionality of the halogen bond correlates with the magnitude of the attraction. Electrostatic interactions are mainly responsible for the directionality of the halogen bond. The directionality of halogen bonds involving iodine and bromine is high, whereas that of chlorine is low and that of fluorine is negligible. The directionality of the halogen bonds in the C₆F₅I– and C₂F₅I–pyridine complexes is higher than that in the hydrogen bonds in the water dimer and water–formaldehyde complex. The calculations suggest that the C? I and C? Br halogen bonds play an important role in controlling the structures of molecular assemblies, that the C? Cl bonds play a less important role and that C? F bonds have a negligible impact.     

Copper(I) complexes of nitrogen-sulphur ligands. 1-Phenyl-4,6-dimethylpyrimidine-2-thione and its protonated form as ligands in copper(I) complexes. Chemical,spectroscopic, conductivity and polarographic studies

Summary 1-Phenyl-4,6-dimethylpyrimidine-2-thione (L) and its protonated cation 1-phenyl-4,6-dimethyl pyrimidinium-2-thione , have been employed to prepare the following copper(I) complexes: CuXL (X=Cl, Br, I, ClO₄ or BF₄), (CuX)₃L₂ (X=Cl, Br, I or SCN), (CuX)₂L₅ (X= ClO₄ or BF₄) and the zwitterionic species CuXY(LH) X=Y=Cl, Br or I; X=Br; Y=Cl; X=I; Y=Br). Chemical analysis, conductivity, and near-and far-i.r. spectroscopic data are presented and the chemical relationships between them discussed in terms of postulated dinuclear or polynuclear species for the complexes. Metalligand vibrations suggest that the neutral ligand is N, S-bidentate in its copper(I) complexes as well as S-coordinat for the cation in the zwitterionic compounds. Diagnostic i.r. bands frequencies of counterions and (Cu–X) modes indicate the coordinating character of Cl^–, Br^–, I^–, SCN^– and of ClO ₄ ^– , BF ₄ ^– (in CuXL) anions. For the chloro-complexes CuClL and (CuCl)₃L₂, salt-like species of the [CuL₂][CuCl₂] and [{Cu₂L₂Cl}_n] [CuCl₂]_n type respectively, are proposed. The polarographic data for the perchlorate complexes have shown that in dimethylformamide (DMF) solution, the prevailing species are CuClO₄L, CuClO₄L₂ and (CuClO₄)₂L₅; their overall stability constants were determined.     

Disordered Crystal Structures of Three Halogenated Propionamides CF3CFXCONH2 (X = Cl, Br, I)

The disordered crystal structures of three halogenated propionamides of the general formula CF₃CFXCONH₂, X = Cl (I), Br (II), and I (III), were studied by X-ray diffraction (CAD-4 automatic diffractometer, MoK ). All these structures are monoclinic with space group P2 _1/c . The structures were solved by direct methods and refined by the full-matrix least-squares procedure anisotropically for nonhydrogen atoms. It was established that structures II and III is isomorphic to each other, whereas structure I is not isomorphic to them, although it has a similar molecular packing. The same crystallographic position is statistically (with different probabilities) occupied by two identical molecules (I, II, or III) with different configurations, which may be regarded as one disordered molecule where two substituents at the C₂ atom (halogen X atom and CF₃ group) are mutually statistically interchangeable in the space of the unit cell. The amide fragment (–CONH₂) of these disordered molecules is practically ordered. The crystal structures of I, II, and III have a developed system of intermolecular H-bonds of N–H O type and unusual intramolecular H-bonds of N–H F–C type.     

Studies on sulfinatodehalogenation: XVII. The sulfinatodehalogenation of primary perfluoroalkyl iodides and bromides by Rongalite

Using acetonitrile or DMF as cosolvent, both perfluoroalkyl iodides such as Cl(CF₂)_nI (n = 4,6,8, la—lc ), CF₃ (CF₂)_n I (n = 5,6,7, ld—lf ), I (CF₂)_n O (CF₂) SO₃ Na(n = 2,4,6, lg—li ) and perfluoroalkyl bromides such as Cl (CF₂)_n Br (n = 4,6, 3a—3b ) and C₇F₁₅ Br (3e) reacted with Rongalite in aqueous solution to give the corresponding sulfinates Cl (CF₂)_n SO₂ Na (n = 4,6,8, 2a—2c ), CF₃-(CF₂)_nSO₂Na (n = 5,6,7, 2d—2f ) and NaO₂S(CF₂)_nO(CF₂)₂SO₃Na (n = 2,4,6, 2g—2i ) in moderate yields. 1 H-perfluoroalkanes were formed as the main products when other solvents such as ethanol. iso-propanol, 1,4-dioxane and morpholine were used.     

The reactions of perfluoro- and α,α-dichloropolyfluoroalkanesulfinates

Sodium perfluoroalkanesulfinate, R_FSO₂Na [R_F?Cl(CF₂)₄, 1a; CF₃(CF₂)₅, 1b; Cl(CF₃)₆, 1c] reacted with bromine in aqueous solution to give the corresponding sulfonyl bromide R_FSO₂Br (2a-2c) and in acetonitrile or acetic acid, to form perfluoroalkyl bromide R_FBr (3a-3c). Heating in acetonitrile at 80°C, 2a-2c were converted smoothly into 3a-3c. However, reaction of sodium α,α-dichloropolyfluoroalkanesulfinate RCCl₂SO₂Na (R?CF₃, Cl(CF₂)n, n=2, 4, 6, 5a-5d) with bromine in aqueous solution gave directly the corresponding bromoalkanes 1-bromo-1,1-dichloropolyfluoroalkane RCCl₂Br (6a-6d). In aqueous potassium iodide solution, 1a-1c, 5a and 5b also reacted with iodine to form the corresponding iodo-polyfluoroalkane 4a-4c, 7a and 7b directly. 6a and 7a underwent free radical addition to alkene readily in the presence of free radical initiator and reacted with Na₂S₂O₄ in the usual way to form α,α-dichloropolyfluoroethane sulfinate (5a). 5a was stable in strong acid, but reacted with strong base to yield 10. 5a was oxidised by hydrogen peroxide to the sulfonate 11 and reduced by zinc in dilute acid to from the α-chloro sulfinate 12.     

Synthese et reactivite d'organomagnesiens perfluores. V.[1] Synthese et identification de nouveaux composes perfluoroalkyles du mercure a chaine longue.

The reaction of mercuric salts HgY₂ or organic mercuric compounds R_HHgX with long chain perfluorinated Grignard reagents R_FMgBr leads to a series of new perfluoroalkyl mercury derivatives with the general formula R_FHgZ (R_F=C₄F₉, C₆F₁₃, C₈F₁₇ ; Z=R_F,R_H,Y with Y = I,Br,Cl, NO₃,OCOCH₃,OCOCF₃).The synthesis of these organomercuric compounds is described, and their spectroscopic properties are reported.     

A NEW EFFICIENT SYNTHESIS OF TRIFLUOROACETYL HALIDES AND MIXED ANHYDRIDES OF PHOSPHORUS AND TRIFLUOROACETIC ACIDS

Abstract

Reaction of trifluoroacetic anhydride with chloroanhydrides of phosphorus acids R₂P(O)CI results in formation of mixed anhydrides R₂P(O) OCOCF₃ and trifluoroacetic acid halides CF₃COX (X=Cl, Br, I) in quantitative yield.     

The Reactivity of CF3C6F4OC6F4Li towards Halogens and Cyanogen Halides

The reaction of 4‐(4′‐trifluoromethyl‐tetrafluorophenoxy)‐tetrafluorophenyllithium (R_FLi, 1 ) with halogens, dicyanogen, cyanogen halides, and xenon difluoride was examined. The corresponding halogenated aromatics R_FCl ( 2 ), R_FBr ( 3 ) and R_FI ( 4 ) were formed upon reaction with chlorine, bromine, and iodine. Essentially the same products were isolated in the reaction of 1 with cyanogen chloride, bromide, and iodide, respectively. The nitrile R_FCN ( 5 ) was obtained from the reaction of 1 with dicyanogen only as a minor product. The reaction of 1 with XeF₂ resulted in the isolation of R_FCH(CH₃)CH₂CH₃ ( 6 ). All products were identified and characterized by analytical and spectroscopic methods. In addition the molecular structures of 2 , 3 , and 4 have been determined by X‐ray crystallography. The reaction enthalpies for the gas phase reactions of pentafluorophenyllithium, C₆F₅Li, as a model for 1 , with XCN (X = F, Cl, Br, I) were calculated.     

Advances in Trifluoromethylating Phosphorus Compounds

Abstract

The System CF₃I/Me₃P is re-investigated and Me₂PCF₃, Me₄P⁺γ, (CF₃)₂PMe₃, Me₃PI₂, [Me₃(CF₃)P]⁺γ are found as products. Using CF₃Br/P(NEt₂)₃ the phosphines R¹ ₂PCF₃ and R¹P(CF₃)₂ (e.g. R¹ = Me, iPr, NEt₂) can be obtained which are precursors either for phosphoranes (e.g. 1,2λ⁵σ⁵-oxaphosphetanes) or phosphonium salts (e.g. [R¹ ₂(Me)PCF₃]⁺X^? or [R¹(Me)P(CF₃)₂X^?]. The latter are deprotonated to furnish methylene phosphoranes R¹ ₂(CH₂=)PCF₃ or R¹(CH₂=)P(CF₃)₂, reactive synthons. From CF₃Br/P(NEt₂)₃/P(OPh)₃ the phosphine P(CF₃)₃ is available, which turned out to be a potent electrophile. Amido phospites ROP(NEt₂)₂ and halides R²X (R²=CCl₂CF₃, X=Cl; R²=CF=CFCF₃, X=F; R²=C₆F₅, X=Br, I; R²=C(CF₃)₃, X=Br; R²=SCF₃, X=CF₃) undergo an ARBUZOV reaction.     

Thermolyse des halogenures de perfluoroalcanesulfonyle

Perfluoroalkanesulfonyl chlorides [R_FSO₂Cl ; R_F  CF₃, C₂F₃, C₄F₉], decompose thermally to give the corresponding perfluoroalkyl chlorides with evolution of SO₂. The latter retards the reaction, but it is catalysed by copper which also inhibits the SO₂ effect. 2-methyl-2-nitrosopropane traps the perfluoroalkyl free radicals. In the presence of a perfluoroalkyl iodide [R′_FI ≠ R′_F≠R_F], other products, R_FI and R_FCl, are obtained. A free radical chain-mechanism is then suggested.On the other hand, perfluorobutanesulfonyl fluoride is very stable thermally.     

Silver‐Catalyzed Formal Insertion of Arynes into RfI Bonds

An unprecedented silver‐catalyzed formal insertion of arynes into R_f?I (R_f=CF₃, C₂F₅) bonds has been developed. This protocol provides easy access to various ortho‐perfluoroalkyl iodoarenes under mild conditions. In this insertion reaction, an ionic atom‐transfer reaction of R_fI occurs, and a silver‐mediated metathesis process is involved in the efficient transfer of the electropositive iodine atom.     

Fluorinated Sulfilimino Iminiums: Efficient and Versatile Sources of Perfluoroalkyl Radicals under Photoredox Catalysis

Reported herein is the use of S‐perfluoroalkyl sulfilimino iminiums as a new source of R_F radicals under visible‐light photoredox catalysis (R_F=CF₃, C₄F₉, CF₂Br, CFCl₂). These shelf‐stable perfluoroalkyl reagents, readily prepared on gram scale from the corresponding sulfoxide using a one‐pot procedure, allow the efficient photoredox‐induced oxyperfluoroalkylation of various alkenes using fac‐Ir(ppy)₃ as the photocatalyst. Importantly, spin‐trapping/electron paramagnetic resonance experiments were carried out to characterize all the radical intermediates involved in this radical/cationic process.     

Studies on sulfinatodehalogenation: IV. The sulfinatodebromination of primary perfluoroalkyl bromides and perfluoroalkylene α, ω-dibromides

Using PTC or cosolvent, both perfluoroalkyl bromides such as Br (CF₂)₂O(CF₂)₂SO₂Na ( 1 ), Br(CF₂)₂OCF₂CO₂H ( 2 ), Cl(CF₂)₄Br ( 3 ), Cl(CF₂Br ( 4 ), n-C₆F₁₃Br ( 5 ), n-C₈F₁₇Br ( 6 ), H(CF₂)₈Br ( 7 ), α, ω-dibromides O(CF₂CF₂Br)₂ ( 8 ), Br(CF₂)₆Br ( 9 ) and Br(CF₂)₈Br ( 10 ) reacted readily with Na₂S₂O₄ in the presence of NaHCO₃ in aqueous solution to form the corresponding perfluoroalkane sulfinates NaO₂S(CF₂)₂O(CF₂)₂SO₂Na ( 11 ), NaO₂S(CF₂)₂OCF₂CO₂Na ( 12 ), Cl(CF₂)₄SO₂Na ( 13 ), Cl(CF₂)₂SO₂Na ( 14 ), n-C₃F₁₃SO₂Na ( 15 ), n-C₈F₁₇SO₂Na ( 16 ), H(CF₂)₈SO₂Na ( 17 ), α, ω-disulfinates O(CF₂CF₂SO₂Na)₂ ( 18 ), NaO₂S(CF₂)₄SO₂Na ( 19 ) and NaO₂S(CF₂)₈SO₂Na ( 20 ) in 66—97% yields. To this new and general reaction of perfluoroalkyl bromides, the name sulfinatodebromination is proposed.     

Studies on fluoroalkylation and fluoroalkoxylation: 2. Perfluoroalkylation of aromatics with perfluoroalkyl iodides in the presence of copper

Perfluoroalkyl iodide R_fI [R_f = (CF₂)_nO(CF₂)₂SO₂F, n = 2, (a); n = 4, (b); (CF₂)₄Cl, (c)] reacted with substituted benzene C₆H₅Y (Y = alkyl, OCH₃, CF₃, F, Cl, Br, I) in the presence of copper in acetic anhydride to give the corresponding mixture of isomeric disubstituted benzene (R_fC₆H₄Y). The conversion and yield depend on both the amount of copper used and nature of substituent. The likely explanation is that the reaction may involve a free radical process. The perfluoroalkyl radical can be trapped by cyclohexene, isopropylbenzene and styrene. Using DMSO in place of acetic anhydride as a solvent the reaction takes a different course, it is believed that the reaction in DMSO proceeds through a perfluoroalkylcopper intermediate.     

Perfluoro and polyfluoroalkanesulfonic acid: XVII. Difluoromethyl perfluoroalkanesulfonates and their reactions

In contrast to R_FSO₃CH₂R(1)(R=hydrogen, alkyl and perfluoroalkyl) and R_FSO₃CF₂R_F′ (2), the reactions of difluoromethyl perfluoroalkanesulfonates RFSO₃CF₂H (3) With nucleophiles are more complicated. Halide inos, X^? (X = F, Cl, I) and ethanol only attack the alkoxyl carbon atom, cleaving the C? O bond to give HCF₂X (4) and HCF₂OEt (5) respectively. Other reagents such as RCO₂^? (R=CH₃, CF₃), C₆H₅S^? etc. can either attack the carbon or sulfur atom of 3 to give the corresponding products of C? O and S? O bond cleavages. More basic nucleophiles RO^? (R = C₆H₅, Et) mainly abstract the proton of the HCF₂ moiety to produce difluorocarbene. Ether and benzene, which can be alkylated by methyl perfluoroalkanesulfonate, do not react with 3 under similar conditions. The reaction rate of 3 with KF is much slower than that of 1 (R = H). All these data seem to indicate that the shielding effect caused by the two fluorine atoms on the methyl carbon in 3 prevents to some extent the nucleophilic attack on this carbon, but not so completely as in 2 due to the presence of a hydrogen atom.