Molecular structure and IR absorption spectra of perfluorinated aldehyde hydrates (n-CxF2x+1CH(OH)2, x = 1-4)

Structures and IR absorption spectra of the conformational isomers of perfluorinated aldehyde hydrates, n-C_xF_2x+1CH(OH)₂, (x = 1-4) have been calculated using density functional theory (DFT) and compared to experimental FT-IR measurements. Two absorption peaks around 3600-3700 cm⁻¹ were observed and are assigned to OH stretching modes of OH groups with, and without, intramolecular hydrogen bonding. For n-C₃F₇CH(OH)₂, two absorption bands around 900-1000 cm⁻¹ were observed in the experimental spectra, whereas only a single in-phase stretching mode of the (CF₃)(C₂F₄CH(OH)₂) and (C₃F₇)(CH(OH)₂) bonds was calculated for each conformer. The experimental spectra were well described by composite spectra of the thermal equilibrium mixture of different conformational isomers of n-C_xF_2x+1CH(OH)₂ calculated by DFT.     

Reaction of trifluoromethylated β-alkoxyenones with tris(trimethylsilyl) phosphite: A temperature influence on regioselectivity

The interaction of tris(trimethylsilyl) phosphite (TMSO)₃P and E-trifluoromethyl-β-alkoxyenones CF₃C(O)CHCHOEt and CF₃C(O)CHC(OMe)Me yielded mixtures of E-1,2- and Z-1,4-adducts, CF₃C(OTMS)[P(O)(OTMS)₂]CCH(OAlk)R 2 and CF₃(OTMS)CCHCR(OAlk)[P(O)(OTMS)₂] 3 where R and Alk = H and Me, or both Me. Conversion of these 1,2-adducts to 1,4-isomers was effected by increased temperature or by exposure to more tris(trimethylsilyl) phosphite. Acid hydrolysis of 2b (R and Alk = Me) gave ketophosphonic acid CF₃C(OH)[P(O)(OH)₂]CH₂COMe in 88% yield, whereas hydrolysis of 2a (R = H and Alk = Et) with KOH in methanol gave CF₃C(OH)[P(O)(OK)₂]CHCHOEt in 37% yield. Acid hydrolysis of 3a (R = H and Alk = Et) and 3b (R and Alk = Me) gave phosphonic acid CF₃C(OH)₂CHCHP(O)(OH)₂ in 82% yield and trifluoromethylated 1,2λ⁵σ⁴-oxaphosphol-3-en.     

A computational study of SbnF5n (n = 1-4): Implications for the fluoride ion affinity of nSbF5

This contributions shows with a series of ab initio MP2 and DFT (BP86 and B3-LYP) computations with large basis sets up to cc-pVQZ quality that the literature value of the standard enthalpy of depolymerization of Sb₄F_20(g) to give SbF_5(g) (+18.5 kJ mol⁻¹) [J. Fawcett, J.H. Holloway, R.D. Peacock, D.R. Russell, J. Fluorine Chem. 20 (1982) 9] is by about 50 kJ mol⁻¹ in error and that the correct value of (Sb₄F_20(g)) is +68 ± 10 kJ mol⁻¹. We assign , , and values for Sb_nF_5n with n = 2-4 and compare the results to available experimental gas phase data. Especially the MP2/TZVPP values obtained in an indirect procedure that rely on isodesmic reactions or the highly accurate compound methods G2 and CBS-Q are in excellent agreement with the experimental data, and reproduce also the fine experimental details at temperatures of 423 and 498 K. With these data and the additional calculation of [Sb_nF_5n+1]⁻ (n = 1-4), we then assessed the fluoride ion affinities (FIAs) of Sb_nF_5n(g), nSbF_5(g), nSbF_5(l) and the standard enthalpies of formation of Sb_nF_5n(g) and [Sb_nF_5n+1]⁻_(g): FIA(Sb_nF_5n(g)) = 514 (n = 1), 559 (n = 2), 572 (n = 3) and 580 (n = 4) kJ mol⁻¹; FIA(nSbF_5(g)) = 667 (n = 2), 767 (n = 3) and 855 (n = 4) kJ mol⁻¹; FIA(nSbF_5(l)) = 434 (n = 1), 506 (n = 2), 528 (n = 3) and 534 (n = 4) kJ mol⁻¹. Error bars are approximately ±10 kJ mol⁻¹. Also the related Gibbs energies were derived. Δ_fH°([Sb_nF_5n+1]⁻_(g)) = −2064 ± 18 (n = 1), −3516 ± 25 (n = 2), −4919 ± 31 (n = 3) and −6305 ± 36 (n = 4) kJ mol⁻¹.     

Synthesis and characterization of (CHCH)n-bridged (n = 1, 2, 3) heterobimetallic and trimetallic ferrocene-ruthenium complexes

A series of heterobinuclear ferrocene-ruthenium complexes Fc(CHCH)_nRuCl(CO)(PMe₃)₃ (n = 1, 3; n = 2, 12), Fc(CHCH)RuCl(CO)(Py)(PPh₃)₂ (4), and trimetallic Fc(CHCH)RuCl(CO)(PPh₃)₂(Py-E-(CHCH)Fc) (6) have been prepared. The length of the molecular rods is extended by successive insertion of CHCH spacers in the bridging ligands or the ancillary ligands. The respective products have been fully characterized and the structures of 3 and 12 have been established by X-ray crystallography. Electrochemical studies have revealed that ethenyl heterobimetallic complexes display two successive one-electron processes, and that intermetallic electronic communication between the two endgroups is attenuated with the increase of the length of the conjugated bridge. The electrochemical behavior of the trimetallic complex reveals strong electronic communication between ruthenium and ferrocene transmitted through the ethenyl bridge, however, it also reveals a very weak interaction between ruthenium and ferrocene transmitted through the (E)-CHCH-Py bridge.     

New stable germylenes, stannylenes, and related compounds: 6. Heteroleptic germanium(II) and tin(II) compounds [(SiMe3)2N-E-OCH2CH2NMe2]n (E = Ge, n = 1; Sn, n = 2): synthesis and structure

New stable heteroleptic germanium(II) and tin(II) compounds [(SiMe₃)₂N-E¹⁴-OCH₂CH₂NMe₂]_n (E¹⁴ = Ge, n = 1 (1), Sn, n = 2 (2)) have been synthesized and their crystal structures have been determined by X-ray diffraction analysis. While compound 1 is monomer stabilized by intramolecular Ge ← N coordination, compound 2 is associated to dimer via intermolecular dative Sn ← O interactions.     

Study of ferrocenyl-substituted Co2(CO)6-bispropargylic alcohol complexes as substrates for the formation of chains and macrocycles

Treatment of [Fc-1-R¹-1′-R²] (R¹ = H, R² = CH(O); R¹ = H, R² = CMe(O); R¹ = R² = CMe(O)) with LiCCCH₂OLi (prepared in situ from HCCCH₂OH and n-BuLi) affords the ferrocenyl-substituted but-2-yne-1,4-diol compounds of general formula [Fc-1-R¹-1′-{CR(OH)CCCH₂OH}] (R¹ = R = H (1a); R¹ = H, R = Me (1b); R¹ = CMe(O), R = Me (1c)) in low to high yields, respectively (where Fc = Fe(η⁵-C₅H₄)₂). In the case of the reactions of [Fc-1-R¹-1′-R²] (R¹ = H, R² = CH(O); R¹ = R² = CMe(O)), the by-products [Fc-1-R¹-1′-{CR(OH)(CH₂)₃CH₃}] (R¹ = R = H (2a); R¹ = CMe(O), R = Me (2c)) along with minor quantities of [Fc-1,1′-{CMe(OH)(CH₂)₃CH₃}₂] (3) are also isolated; a hydrazide derivative of dehydrated 2c, [1-(CMeCHCH₂CH₂CH₃)-1′-(CMeNNH-2,4-(NO₂)₂C₆H₃)] (2c′), has been crystallographically characterised. Interaction of 1 with Co₂(CO)₈ smoothly generates the alkyne-bridged complexes [Fc-1-R¹-1′-{Co₂(CO)₆-μ-η²-CR(OH)CCCH₂OH}] (R¹ = R = H (4a); R¹ = H, R = Me(4b); R¹ = CMe(O), R = Me (4c)) in good yield. Reaction of 4a with PhSH, in the presence of catalytic quantities of HBF₄ · OEt₂, gives the mono- [Fc-1-H-1′-{Co₂(CO)₆-μ-η²-CH(SPh)CCCH₂OH}] (5) and bis-substituted [Fc-1-H-1′-{Co₂(CO)₆-μ-η²-CH(SPh)CCCH₂SPh}] (6) straight chain species, while with HS(CH₂)_nSH (n = 2,3) the eight- and nine-membered dithiomacrocylic complexes [Fc-1-H-1′-{cyclo-Co₂(CO)₆-μ-η²-CH(S(CH₂)_n-)CCCH₂S-}] [n = 2 (7a), n = 3 (7b)] are afforded. By contrast, during attempted macrocyclic formation using 4b and HSCH₂CH₂OCH₂CH₂SH dehydration occurs to give [Fc-1-H-1′-{Co₂(CO)₆-μ-η²-C(CH₂)CCCH₂OH}] (8). Single crystal X-ray diffraction studies have been reported on 2c′, 4b, 4c, 7b and 8.     

Atmospheric chemistry of CF3CFCH2: Products and mechanisms of Cl atom and OH radical initiated oxidation

The products of Cl atom and OH radical initiated oxidation of CF₃CFCH₂ were studied in 700 Torr of N₂/O₂ diluent at 296 ± 1 K. The reactions of Cl atoms and OH radicals with CF₃CFCH₂ proceed via electrophilic addition to the double bond. The reaction with chlorine atoms proceeds 56 ± 5% via addition to the central carbon. The chlorine atom initiated oxidation of CF₃CFCH₂ gives CF₃C(O)F in a molar yield which is indistinguishable from 100% and independent of [O₂], and HC(O)Cl in a molar yield which increased from 30% to 59% as [O₂] was increased from 3 to 700 Torr. The OH radical initiated oxidation of CF₃CFCH₂ gives CF₃C(O)F as major product in a yield of 91 ± 6%. The results are discussed with respect to the atmospheric chemistry and environmental impact of CF₃CFCH₂.     

Synthesis and crystal structures of the first germanium-containing alkylidene complexes of molybdenum R3Ge-CHMo(NAr)(OR′)2 (R = Me, Ph) with direct germanium-carbene carbon bond

The novel germanium-containing alkylidene complexes of molybdenum R₃Ge-CHMo(NAr)(OCMe₂CF₃)₂ (Ar = 2,6-i-Pr₂C₆H₃; R = Me, Ph) have been prepared by the reaction of organogermanium vinyl reagents R₃ GeCHCH₂ with known alkylidene compounds Alkyl-CHMo(NAr)(OCMe₂CF₃)₂ (Alkyl = Bu^t, PhMe₂C). The titled compounds were isolated as crystalline solids and characterized by elemental analysis, ¹H NMR, ¹³C NMR spectroscopy and X-ray diffraction studies. The geometry of the Mo atoms in the compounds can be described as a distorted tetrahedron.     

Theoretical study on the substitution and insertion reactions of silylenoid H2SiLiF with CH3XHn−1 (X = F, Cl, Br, O, N; n = 1, 1, 1, 2, 3)

The substitution and insertion reactions of H₂SiLiF (A) with CH₃XH_n−1 (X = F, Cl, Br, O, N; n = 1, 1, 1, 2, 3) have been studied using density functional theory. The results indicate that the substitution reactions of A with CH₃XH_n−1 proceed via two reaction paths, I and II, forming the same product H₂SiFCH₃. The insertion reactions of A with CH₃XH_n−1 form H₂SiXH_n−1CH₃. The following conclusions emerge from this work. (i) The substitution reactions of A with CH₃XH_n−1 occur in a concerted manner. The substitution barriers of A with CH₃XH_n−1 for both pathways decrease with the increase of the atomic number of the element X for the same family systems or for the same row systems. Path I is more favorable than path II. (ii) A inserts into a C-X bond via a concerted manner, and the reaction barriers increase for the same-row element X from right to left in the periodic table, whereas change very little for the systems of the same-family element X. (iii) The substitution reactions occur more readily than the insertion reactions for A with CH₃XH_n−1 systems. (iv) All substitution and insertion reactions of A with CH₃XH_n−1 are exothermic. (v) In solvents, the substitution reaction process of A with CH₃XH_n−1 is similar to that in vacuum. The barrier heights in solvents increase in the order CH₃F < CH₃Cl < CH₃Br < CH₃OH < CH₃NH₂. The solvent polarity has little effects on the substitution barriers. The calculations are in agreement with experiments.     

Intermolecular hydrogen bonding in the binary mixture [(C2H5)2CO + CH3OH] probed by polarized Raman measurements and DFT calculations

The Raman spectra of neat (C₂H₅)₂CO (pentanone) and its binary mixtures with hydrogen donor solvent (CH₃OH), [(C₂H₅)₂CO + CH₃OH] having different mole fractions of the reference system, (C₂H₅)₂CO in the range 0.1-0.9 at a regular interval of 0.1 were recorded in the CO stretching region. In neat liquid, the Raman peak appears asymmetric. The asymmetric nature of the peak has been attributed to the CO stretching mode of the two conformers of (C₂H₅)₂CO having C₂ and C_2v point groups and the corresponding bands at ∼1711 and ∼1718 cm⁻¹, respectively. A careful analysis of the I_iso (isotropic component of the Raman scattered intensity) at different concentrations reveals that upon dilution with methanol, at mole fraction C = 0.6, an additional peak in the CO stretching region is observed at ∼1703 cm⁻¹ which is attributed to the hydrogen bonding with methanol. A peculiar feature in this study is that upon dilution, the peak at ∼1718 cm⁻¹ shows a minimum at C = 0.6, but on further dilution it shows a blue shift. However, the other peak at ∼1711 cm⁻¹ shows a continuous red shift with dilution as well as a maximum at C = 0.7 in the linewidth vs. concentration plot, which is essentially due to competition between motional narrowing and diffusion phenomena. A significant amount of narrowing in the Raman band at ∼1718 cm⁻¹ can be understood in terms of caging effect of the reference molecule by the solvent molecules at high dilution. A density functional theoretic (DFT) calculation on optimized geometries and vibrational frequencies of two conformers of neat (C₂H₅)₂CO in C₂ ad C_2v forms and the complexes with one and two CH₃OH molecules with both the conformers was performed. The experimental results and theoretical calculations together indicate a co-existence of two conformers as well as hydrogen bonded complex with methanol in the binary mixture, [(C₂H₅)₂CO + CH₃OH] at intermediate concentrations.     

Reactivity of TpRu(L)(NCMe)R (L = CO, PMe3; R = Me, Ph) systems with isonitriles: Experimental and computational studies toward the intra- and intermolecular hydroarylation of isonitriles

The Ru(II) phenyl complex TpRu(PMe₃)(NCMe)Ph {Tp = hydridotris(pyrazolyl)borate} reacts with isonitriles to form complexes of the type TpRu(PMe₃)(CNR)Ph (R = ^tBu, CH₂Ph, CH₂CH₂Ph). Neither thermal nor photolytic reactions of these systems with excess isonitrile and benzene resulted in the production of corresponding imines. DFT studies that probed the energetics of the desired catalytic transformations revealed that (Tab)Ru(PH₃)(CNCH₂CH₂Ph)Ph {Tab = tris(azo)borate} is the most stable species in a proposed catalytic cycle. Exclusive of calculated transition states, the highest points on the calculated free energy surface are 34 kcal/mol, for (Tab)Ru(PH₃)(o,η²-C,C-CNCH₂CH₂Ph)Ph {relative to the starting material (Tab)Ru(PH₃)(CNCH₂CH₂Ph)Ph}, and 27 kcal/mol for the C-H activation product (Tab)Ru(PH₃)(o-C₆H₄CH₂CH₂NC) and benzene. The substantial increases in free energy result primarily from the loss of the stable ruthenium-η¹-isonitrile interaction.     

Novel generation ponytails in fluorous chemistry: Syntheses of primary, secondary, and tertiary (nonafluoro-tert-butyloxy)ethyl amines

(Nonafluoro-tert-butyloxy)ethyl tosylate 4 was prepared in 65% yield from nonafluoro-tert-butanol 1 using commercially available reagents. Further reaction of 4 with HNR¹R² (R¹ = R² = H, CH₃; R¹ = H, R² = CH₃, (CH₂)₃C₈F₁₇, CH₂CH₂OC(CF₃)₃) affords the appropriate (CF₃)₃COCH₂CH₂NR¹R² amines in 20-69% yields. Improved overall yields of [(CF₃)₃COCH₂CH₂]_3−nNR_n to 1 were obtained by the reaction of (CF₃)₃CONa 2 and (XCH₂CH₂)_3−nNR_n (X = Cl, n = 0, 1, 2, R = CH₃; X = CH₃SO₂O, n = 1, R = CH₃SO₂) nitrogen mustards and a similar reactive β-substituted ethyl amine. The title amines are mobile colorless liquids and volatile with steam. The bulky fluorous ponytail (CF₃)₃CO(CH₂)₂ displays high acidic stability and increases fluorous character almost as much as the classical straight-chain C₈F₁₇(CH₂)₃ ponytail.     

Bis(perfluoroorganyl)bromonium salts [(RF)2Br]Y (RF = aryl, alkenyl, and alkynyl)

Bromonium salts [(R_F)₂Br]Y with perfluorinated groups R_FC₆F₅, CF₃CFCF, C₂F₅CFCF, and CF₃C≡C were isolated from reactions of BrF₃ with R_FBF₂ in weakly coordinating solvents (wcs) like CF₃CH₂CHF₂ (PFP) or CF₃CH₂CF₂CH₃ (PFB) in 30-90% yields. C₆F₅BF₂ formed independent of the stoichiometry only [(C₆F₅)₂Br][BF₄]. 1:2 reactions of BrF₃ and silanes C₆F₅SiY₃ (Y = F, Me) ended with different products - C₆F₅BrF₂ or [(C₆F₅)₂Br][SiF₅] - as pure individuals, depending on Y and on the reaction temperature (Y = F). With C₆F₅SiF₃ at ≥−30 °C [(C₆F₅)₂Br][SiF₅] resulted in 92% yield whereas the reaction with less Lewis acidic C₆F₅SiMe₃ only led to C₆F₅BrF₂ (58%). The interaction of K[C₆F₅BF₃] with BrF₃ or [BrF₂][SbF₆] in anhydrous HF gave [(C₆F₅)₂Br][SbF₆]. Attempts to obtain a bis(perfluoroalkyl)bromonium salt by reactions of C₆F₁₃BF₂ with BrF₃ or of K[C₆F₁₃BF₃] with [BrF₂][SbF₆] failed. The 3:2 reactions of BrF₃ with (C₆F₅)₃B in CH₂Cl₂ gave [(C₆F₅)₂Br][(C₆F₅)_nBF_4−n] salts (n = 0-3). The mixture of anions could be converted to pure [BF₄]⁻ salts by treatment with BF₃·base.     

The reaction of the group-13 alkyls ER3 (E = Al, Ga, In; R = CH2t-Bu, CH2 SiMe3) with the platinum-complex [(dcpe)Pt(H)(CH2t-Bu)]

The reactions of the sterically demanding group-13 alkyls ER₃ (E = Al, Ga, In; R = CH₂t-Bu, CH₂SiMe₃) with the platinum-complex [(dcpe)Pt(H)(CH₂t-Bu)] were re-investigated. The bimetallic compounds [(dcpe)Pt(ER₂)(R)] (3: E = Ga, R = CH₂SiMe₃; 5: E = In, R = CH₂t-Bu; dcpe = bis(dicyclohexylphosphino)ethane) with direct σ(Pt-E) bonds were obtained by oxidative addition of an E-C bond to the coordinatively unsaturated fragment [(dcpe)Pt] produced in situ by thermolysis of the starting complex [(dcpe)Pt(CH₂t-Bu)(H)]. The single crystal structure determination reveals a Pt-Ga bond length of 2.376(2) Å and a Pt-In bond length of 2.608(1) Å. All new compounds were characterised by elemental analysis, ³¹P and ¹⁹⁵Pt NMR spectroscopy. Interestingly, the Pt-Ga compound 3 slowly transforms into the platinum alkyl/hydride isomer {(dcpe)Pt(μ₂-H)[CH₂Si(CH₃)₂ CH₂Ga(CH₂SiMe₃)₂]} (4) during crystallization from solution at room temperature. The X-ray single crystal structure analysis revealed both complexes 3 and 4 coexisting in the unit cell in a 1:1 relation. The inaccessibility of analytically pure samples of the Pt-Al complex {(dcpe)Pt[Al(CH₂t-Bu)₂](CH₂t-Bu)} (6), postulated as intermediate of the reaction of [(dcpe)Pt(H)(CH₂t-Bu)] with Al(CH₂t-Bu) on the basis of ³¹P and ¹⁹⁵Pt NMR data, is attributed to an enhanced tendency to isomerisation into the alkyl/hydride Pt/Al congener of 4. A brief DFT analysis of the bonding situation of the model complex [(dhpe)Pt(GaMe₂)(Me)] (1M) revealed, that the contribution of π(Pt-Ga) back-bonding is negligible.     

Preparation, crystal structures, EPR and reflectance spectra of two new charge-transfer salts, [CpFeCpCH2N(CH3)3]4[XMo12O40] · nCH3CN (n = 0 for X = P or n = 1 for X = Ge)

Two new charge-transfer salts, [CpFeCpCH₂N(CH₃)₃]₄[PMo₁₂O₄₀] · CH₃CN (1) and [CpFeCpCH₂N(CH₃)₃]₄[GeMo₁₂O₄₀] (2), were synthesized by the traditional solution synthetic method and their structures were determined by single-crystal X-ray analysis. Salt 1 belongs to the triclinic space group P1, and salt 2 belongs to the triclinic space group . There exist the complex interactions of the cationic ferrocenyl donor and Keggin polyanion in the solid state. The solid state UV-Vis diffuse reflectance spectra indicate the presence of a charge-transfer band climbing from 450 nm to well beyond 900 nm for 1, a charge-transfer band from 460 to 850 nm with λ_max = 630 nm for 2.The EPR spectra of salts 1 and 2 at 77 K show a signal at g = 2.0048 and 1.9501, respectively, ascribed to the delocalization of one electron in reduced Keggin ion in salt 1 and the Mo^VI in [GeMo₁₂O₄₀]⁴⁻ is partly reduced to Mo^V owing to the charge-transfer transitions taking place between the ferrocenyl donors and the POM acceptors. The two compounds were also characterized by IR spectroscopy and cyclic voltammetry.     

Fluorous modification of 2,2′-bipyridine

A series of 2,2′-bipyridines featuring fluorinated alkyl groups [(CH₂)₃(CF₂)_xCF₃: x = 0, (1); 5, (2); 7, (3); 9 (4)] appended in the 4 and 4′ positions have been prepared. 1-4 were characterized by spectroscopy and physical methods including partition coefficient (biphase: perfluoromethylcyclohexane/toluene) and cyclic voltammetry (THF). Ab-initio calculations of vertical ionization potentials (VIPs) for 1-4 confirm the insulating role of the methylene spacers as the electrochemical reduction potentials of 1-4 are almost identical to that of 2,2′-bipyridine. Calculations for (CH₂)_nCF₃ derivatives (n = 0-10) describe a limit for impact of the CF₃ group through 9-10 methylenes. From both physical and theoretical data fluorinated alkyl groups of the formula (CH₂)₃(CF₂)_xCF₃ [x = 0-9] are inductively equivalent to a hydrogen substituent when appended to the bipyridine moiety.     

Triadic analysis of substituent effects—gas-phase acidity of para-substituted phenols

A large variety of para-substituted phenols was examined and their acidities in the gas-phase were rationalized by a triadic formula, which is capable of delineating the initial, intermediate and final state effects in the deprotonation process. It is shown that triadic analysis is equivalent to the homodesmotic reactions approach, while being much more informative at the same time. The applied MP2(fc)/6-311+G(d,p)//B3LYP/6-31G(d) theoretical method gives acidities in very good agreement with available measured values, meaning that calculations can safely replace the missing experimental data for compounds not easily amenable to laboratory examinations. It is found that the underlying principle leading to enhanced acidity of para-substituted phenols containing strong π-electron acceptor groups is the final state effect. It reflects a more pronounced ability to accommodate the excess negative charge. Particular attention has been focused on superacidifying NO₂, SO₂CF₃ and S(O)(NSO₂CF₃)CF₃ and C(CN)C(CN)₂ moieties. It is shown that their influence on acidity is strong and that the deprotonation ability increases along the sequence of substituents NO₂<SO₂CF₃<S(O)(NSO₂CF₃)CF₃<C(CN)C(CN)₂. On the contrary, the electron releasing substituents NH₂, OCH₃, OH and CH₃ decrease acidity of phenol albeit to a small extent. Finally, it is demonstrated that pentacyano derivative of phenol is a powerful OH superacid as evidenced by ΔH_acid value of 287.5 kcal mol⁻¹.     

New types of asymmetrical bromonium salts [RF(RF′)Br]Y where RF and/or RF′ represent perfluorinated aryl, alkenyl, and alkynyl groups

A series of previously unknown asymmetrical fluorinated bis(aryl)bromonium, alkenyl(aryl)bromonium, and alkynyl(aryl)bromonium salts was prepared by reactions of C₆F₅BrF₂ or 4-CF₃C₆H₄BrF₂ with aryl group transfer reagents Ar′SiF₃ (Ar′ = C₆F₅, 4-FC₆H₄, C₆H₅) or perfluoroorganyl group transfer reagents R_F′BF₂ (R_F = C₆F₅, trans-CF₃CFCF, C₃F₇C≡C) preferentially in weakly coordinating solvents (CCl₃F, CCl₂FCClF₂, CH₂Cl₂, CF₃CH₂CHF₂ (PFP), CF₃CH₂CF₂CH₃ (PFB)). The presence of the base MeCN and the influence of the adducts R_F′BF₂·NCMe (R_F = C₆F₅, CF₃C≡C) on reactions aside to bromonium salt formation are discussed. Reactions of C₆F₅BrF₂ with Alk_F′BF₂ in PFP gave mainly C₆F₅Br and Alk_F′F (Alk_F′ = C₆F₁₃, C₆F₁₃CH₂CH₂), presumably, deriving from the unstable salts [C₆F₅(Alk_F′)Br]Y (Y = [Alk_F′BF₃]⁻). Prototypical reactivities of selected bromonium salts were investigated with the nucleophile I^-and the electrophile H⁺. [4-CF₃C₆H₄(C₆F₅)Br][BF₄] showed the conversion into 4-CF₃C₆H₄Br and C₆F₅I when reacted with [Bu₄N]I in MeCN. Perfluoroalkynylbromonium salts [C_nF_2n+1C≡C(R_F)Br][BF₄] slowly added HF when dissolved in aHF and formed [Z-C_nF_2n+1CFCH(R_F)Br][BF₄].