Robust S4⋅⋅⋅O Supramolecular Synthons: Structures of Radical-Radical Cocrystals [p-XC6F4CNSSN]2[TEMPO] (X=F,Cl, Br,I, CN)

Cocrystallization of the dithiadiazolyl (DTDA) radicals p-XC₆F₄CNSSN (X=F, Cl, Br, I, CN) with TEMPO afforded the 2 : 1 cocrystals [p-XC₆F₄CNSSN]₂[TEMPO] ( 1 – 5 ) whose structures all reflect a common S₄⋅⋅⋅O supramolecular motif. The nature of this interaction was probed by DFT calculations (M06/aug-cc-pVDZ) on 1 which revealed that the enthalpy of formation of the [C₆F₅CNSSN]₂[TEMPO] supramolecular motif from [C₆F₅CNSSN]₂ and TEMPO is substantial (−54.0 kJ mol⁻¹). Electronic structure calculations revealed a TEMPO-based doublet S= configuration as the ground state with limited spin density on the DTDA rings (2.4 %). The corresponding spin quartet state is +78.9 kJ mol⁻¹ higher in energy. An atoms-in-molecules analysis reveals four bond critical points (BCPs) between the TEMPO O and the DTDA S atoms as well as additional BCPs between selected DTDA S atoms and methyl H atoms of the TEMPO molecule. Herein, the structures of 2 – 5 are considered within the context of a hierarchical view of competing and complementary intermolecular interactions; in particular, the established supramolecular CN⋅⋅⋅S−S synthon is sacrificed in order to form the new S₄⋅⋅⋅O interaction.     

Strukturen von Bis(trifluormethyl)halogeno‐ und ‐thiocyanato‐mercuraten, [Hg(CF3)2X]— (X = Br,I, SCN), und ein Vergleich der Strukturparameter der CF3‐Gruppen

Structures of Bis(trifluoromethyl)halogeno and thiocyanato Mercurates, [Hg(CF₃)₂X]^— (X = Br, I, SCN), and a Comparison of the Structural Parameters of the CF₃ Groups [(18‐C‐6)K]₂[Hg(CF₃)₂SCN]₂ (1) and [P(CH₃)(C₆H₅)₃]₂[Hg(CF₃)₂X]₂ (X = Br (2) , I (3) ) are prepared and their crystal structures are determined. [(18‐C‐6)K]₂[Hg(CF₃)₂SCN]₂ (1) crystallizes in the monoclinic space group P2₁/c with Z = 2, [P(CH₃)(C₆H₅)₃]₂[Hg(CF₃)₂Br]₂ (2) in the monoclinic space group P2₁/n with Z = 2 and [P(CH₃)(C₆H₅)₃]₂[Hg(CF₃)₂I]₂ (3) in the triclinic space group P1¯ with Z = 1. In the solid state the three compounds form dimeric anions with planar Hg₂X₂ rings. The structural parameters of the Hg(CF₃)₂ units in the till now known bis(trifluoromethyl)halogeno mercurates are compared. In all compounds one nearly symmetric and one distorted CF₃ group exist. The largest differences of the C—F bond lengths is found for [(18‐C‐6)K][Hg(CF₃)₂I]. This can be regarded as the experimental evidence for the properties of trifluoromethyl mercury compounds to act as excellent difluorocarbene sources in the presence of alkali iodides.     

Synthesis,Reactivity and Structural Properties of Trifluoromethylphosphoranides

Phosphoranides are interesting hypervalent species which serve as model compounds for intermediates or transition states in nucleophilic substitution reactions at trivalent phosphorus substrates. Herein, the syntheses and properties of stable trifluoromethylphosphoranide salts are reported. [K(18-crown-6)][P(CF₃)₄], [K(18-crown-6)][P(CF₃)₃F], and [NMe₄][P(CF₃)₂F₂] were obtained by treatment of trivalent precursors with sources of CF₃⁻ or F⁻ units. These [P(CF₃)_4-nF_n]⁻ (n=0–2) salts exhibit fluorinating (n=1–2) or trifluoromethylating (n=0) properties, which is disclosed by studying their reactivity towards selected electrophiles. The solid-state structures of [K(18-crown-6)][P(CF₃)₄] and [K(18-crown-6)][P(CF₃)₃F] are ascertained by single crystal X-ray crystallography. The dynamics of these compounds are investigated by variable temperature NMR spectroscopy.     

Fluoroborates by Cleavage of Trimethylamine‐bis(trifluoromethyl)boranes with NEt3 × 3 HF. Structures of C6F5(CF3)2B · NMe3, K[C6H5CH2(CF3)2BF], and K[C6H5(CF3)2BF]

Trimethylamine‐bis(trifluoromethyl)boranes R(CF₃)₂B · NMe₃ (R = cis/trans‐CF₃CF=CF ( 1/2 ), HC≡C ( 3 ), H₂C=CH ( 4 ), C₂H₅ ( 5 ), C₆H₅CH₂ ( 6 ), C₆F₅ ( 7 ), C₆H₅ ( 8 )) react with NEt₃ × 3 HF depending on the nature of R at 155–200 °C under replacement of the trimethylamine ligand to form the corresponding fluoro‐bis(trifluoromethyl)borates [R(CF₃)₂BF]^– ( 1 a/2 a – 8 a ). The structures of 7 , K[C₆H₅CH₂(CF₃)₂BF] ( K‐6 a ), and K[C₆H₅(CF₃)₂BF] ( K‐8 a ) have been investigated by single‐crystal X‐ray diffraction. In 7 the CF₃ groups make short repulsive contacts with NMe₃ and C₆F₅ entities – the B–CF₃ bonds being unusually long. The B–F bond lengths of K‐6 a and K‐8 a (1.446(3) and 1.452(2) Å, respectively) are long for a fluoroborate.     

Low-temperature heat capacity of hydrophilic ionic liquids [BMIM][CF3COO] and [BMIM][CH3COO] and a correlation scheme for estimation of heat capacity of ionic liquids

Heat capacity for 1-butyl-3-methylimidazolium trifluoroacetate [bmim][CF₃COO] and acetate [bmim][CH₃COO] in the temperature range of (5 to 370) K has been measured by adiabatic calorimetry. Temperatures and enthalpies of phase transitions in [bmim][CF₃COO] have been determined. Thermodynamic functions for the compounds in the condensed state have been calculated. Physicochemical properties for the studied ionic liquids and alkali acetate salts have been compared. The correlation scheme for estimation of C_p of ionic liquids in a range of (190 to 370) K has been developed.     

Eine neue Synthese für Nitrosyl‐Salze mit schwach koordinierenden Anionen am Beispiel von NO[B(CF3)4]

A New Synthesis for Nitrosyl Salts with Weakly Coordinating Anions Exemplified by NO[B(CF₃)₄] A new synthesis for nitrosyl salts of weakly coordinating anions is described, using the corresponding guanidinium salts as starting materials. The guanidinium salt [C(NH₂)₃][B(CF₃)₄] was obtained by a metathesis reaction of K[B(CF₃)₄] with [C(NH₂)₃]Cl. Treatment of the guanidinium salt with liquid NO₂ resulted in analytical pure NO[B(CF₃)₄] in quantitative yield. The guanidinium and nitrosyl tetrakis(trifluormethyl)borates were characterized by vibrational and NMR spectroscopy as well as by DSC measurements.     

The infrared spectra of gaseous 1,1,3,3-tetrachlorotetrafluoro-4-(trifluoromethyldioxy)butyl trifluoromethyl ether and 1,1,3,3-tetrachlorotetrafluoro-1,4-bis(trifluoromethoxy)butane

1,1,3,3-Tetrachlorotetrafluoro-4-(trifluoromethyldioxy)butyl trifluoromethyl ether, CF₃O(CF₂CCl₂)₂O₂CF₃, was formed as one of the products in the reaction of CF₃O₃CF₃ with CF₂CCl₂ at 322.6 - 342.5 K. It was isolated by fractional condensation between 213 and 243 K and characterized by molecular weight determination and ¹⁹F NMR spectrum. 1,1,3,3-Tetrachlorotetrafluoro-1,4-bis(trifluoromethoxy)butane, CF₃O(CF₂CCl₂)₂OCF₃, was condensed as residue at 193 K from the reaction of CF₃OF with CF₂CCl₂ at 266 - 302.7 K, when [CF₂CCl₂]/[CF₃OF] ≦ 0.5. It was characterized by gas chromatography and molecular weight determination. The infrared spectra of both compounds are given, providing additional support for their characterization.     

Relative rate constants for reactions of HFC 152a, 143, 143a, 134a,and HCFC 124 with F or Cl atoms and for CF2CH3, CF2HCH2, and CF3CFH radicals with F2, Cl2, and O2

Relative rate experiments using UV photolysis of F₂ or Cl₂ have been used to determine rate constant ratios for several hydrofluorocarbon (HFC) reactions with Cl or F atoms and for HFC alkyl radicals with molecular halogens. For mixtures with F₂ present, dark reactions are, also, observed which are attributed to thermal dissociation of the F₂ to form F atoms. At 296 K, the rate of reaction (1a) [CF₂HCH₃ + F → CF₂CH₃ + HF] relative to (1b) [CF₂HCH₃ + F → CF₂HCH₂ + HF] is k_1a/k_1b = 0.73 (±0.13) and is independent of T (= 262–348 K). At 296 K, the ratio of reaction (2a) [CF₂HCH₂F + F → products] to that of (k_1a + k_1b) is (k_1a + k_1b)/k_2a = 2.7 (±0.4), and for reaction (2b) [CF₃CH₃ + F → products] (k_1a + k_1b)/k_2b = 22 ± 12. The temperature dependence (263–365 K) of the rate constant of reaction (3) [CF₃CFH₂ + Cl → products] relative to reaction (4) [CF₃CFClH + Cl → products] is k₃/k₄(±10%) = 1.55 exp(?300 K/T). For the alkyl radicals formed from HFC 152a (CF₂HCH₂ and CF₂CH₃) and from HFC 134a (CF₃CFH), rate constants for the reactions with F₂ and Cl₂ were measured relative to their reactions with O₂. The rate constant of reaction (5cl) [CF₂CH₃ + Cl₂ → CF₂ClCH₃ + Cl] relative to (5o) [CF₂CH₃ + O₂ → CF₂(O₂)CH₃] is k_5cl/k_5o(±15%) = 0.3 exp(200 K/T). For reaction (5f) [CF₂CH₃ + F₂ → CF₃CH₃ + F], k_5f/k_5o(±35%) = 0.23. The ratio for reaction (6f) [CF₂HCH₂ + F₂ → CF₂HCH₂F + F] relative to (6o) [CF₂HCH₂ + O₂ → CF₂HCH₂O₂] is k_6f/k_6o(±40%) = 1.23 exp(?730 K/T). The rate constant ratio for reaction (8cl) [CF₃CFH + Cl₂ → CF₃CFClH + Cl] relative to reaction (8o) [CF₃CFH + O₂ → CF₃CFHO₂] is k_8cl/k_8o(±18%) = 0.16 exp(?940 K/T). For reaction (8f) [CF₃CFH + F₂ → CF₃CF₂H + F], k_8f/k_8o(±35%) = 0.6 exp(?860 K/T). © 1993 John Wiley & Sons, Inc.     

Reaktionen eines Tetraalkoxyhydro-spirophosphorans

Reactions of a Tetraalkoxy Hydrospirophosphorane The hydrophosphorane HP[OC(CF₃)₂C(CF₃)₂O]₂ is oxidized by dimethylsulfoxide to form a hydroxy phosphorane, which may be silylated easily. Chlorine and bromine react to give the corresponding halo spirophosphoranes. FP[OC(CF₃)₂C(CF₃)₂O]₂ is obtained from FPCl₂[OC(CF₃)₂C (CF₃)₂O] and Li₂[OC(CF₃)₂C(CF₃)₂O]. In the presence of triethyl amine HP[OC(CF₃)₂C(CF₃)₂O]₂ is converted by benzylbromide or acetylchloride to RP[OC(CF₃)₂C(CF₃)₂O]₂ (R ? PhCH₂, MeC(O)). Trimethylphosphine performs an acid-base reaction producing a thermally unstable Me₃PH⁺{P[OC(CF₃)₂C(CF₃)₂O]₂}^?. The hydrolysis of the parent compound gives phosphorous acid and perfluoropinacole.     

Substituenteneffekte auf azido-tetrazolo-gleichgewichte elektronische und sterische effekte bei s-triazolo[4,3-c]tetrazolo[1,5-a]pyrimidinen1

The azido tetrazolo valence isomerism of twenty 9-methyl-s-triazolo[4,3-c]tetrazolo[1,5-a]pyrimidines with different substituents at position 5 has been studied by means of ¹H NMR spectroscopy. All the compounds have been found to be tetrazoles in the solid state and in (CD₃)₂SO solution; in CF₃COOH azido and tetrazolo isomers are in equilibrium. From equilibrium constants K and thermodynamic data determined it is concluded that in this series K depends on both electronic effects and steric requirements of the 5-substituents. A linear relation between K and σ was found for 5-arylderivatives because ΔS° keeps approximately constant and the substituent mainly operates on ΔH°.     

Preparation of 1‐X‐2, 2‐Difluoroethenylxenon(II) Tetrafluoroborates [CF2=CXXe][BF4]

The new type of alkenylxenon(II) salts [CF₂=CXXe] [BF₄] (X = H, Cl, CF₃) was prepared by reacting the corresponding alkenyldifluoroboranes CF₂=CXBF₂ with XeF₂ in 1, 1, 1, 3, 3‐pentafluoropropane (PFP) at —60 °C. The alkenylxenon(II) salts were characterised by multinuclear NMR spectroscopy. The influence of the substituent X at C‐1 on the stability of alkenylxenon(II) salts is discussed. Additionally the preparation of the potassium alkenyltrifluoroborate salts K [CF₂=CXBF₃] and their transformation into the boranes CF₂=CXBF₂ by fluoride abstraction in PFP is reported.     

Tunning CO2 Separation Performance of Ionic Liquids through Asymmetric Anions

This work aims to explore the gas permeation performance of two newly-designed ionic liquids, [C₂mim][CF₃BF₃] and [C₂mim][CF₃SO₂C(CN)₂], in supported ionic liquid membranes (SILM) configuration, as another effort to provide an overall insight on the gas permeation performance of functionalized-ionic liquids with the [C₂mim]⁺ cation. [C₂mim][CF₃BF₃] and [C₂mim][CF₃SO₂C(CN)₂] single gas separation performance towards CO₂, N₂, and CH₄ at T = 293 K and T = 308 K were measured using the time-lag method. Assessing the CO₂ permeation results, [C₂mim][CF₃BF₃] showed an undermined value of 710 Barrer at 293.15 K and 1 bar of feed pressure when compared to [C₂mim][BF₄], whereas for the [C₂mim][CF₃SO₂C(CN)₂] IL an unexpected CO₂ permeability of 1095 Barrer was attained at the same experimental conditions, overcoming the results for the remaining ILs used for comparison. The prepared membranes exhibited diverse permselectivities, varying from 16.9 to 22.2 for CO₂/CH₄ and 37.0 to 44.4 for CO₂/N₂ gas pairs. The thermophysical properties of the [C₂mim][CF₃BF₃] and [C₂mim][CF₃SO₂C(CN)₂] ILs were also determined in the range of T = 293.15 K up to T = 353.15 K at atmospheric pressure and compared with those for other ILs with the same cation and anion’s with similar chemical moieties.     

A model for the etching of Si in CF4 plasmas: Comparison with experimental measurements

A model has been developed to describe the chemistry which occurs in CF₄ plasmas and the etching of Si both in the plasma and downstream. One very important feature of this model is that for discharge residence times which vary by more than an order of magnitude, the amount of CF₄ consumed is low and relatively constant. This is because the gas-phase combination reactions between F and both CF₃ and CF₂ lead to the rapid reforming of CF₄. The model predicts that CF₂ is a major species in the gas phase and that the [F] detected as a sample point downstream is a very sensitive function of [CF₂]/[F] in the discharge. Even though the calculations show that [F] in the discharge varies only slightly over the wide range of experimental conditions considered, large variations in [F] at the sample point occur because the [CF₂]/[F] ratio in the discharge changes. The concentrations of C₂F₆ and SiF₄ are predicted to within a factor of 2 over a very wide range of experimental conditions. This confirms the importance of gas-phase free radical reactions in the etching of Si.     

A new method for the preparation of perfluorocarboxylic acids

The reaction of both primary perfluoroalkyl iodides and bromides containing 3 ∼ 12 carbon atoms [CF₃(CF₂)_nX, n = 2 ∼ 11, X = Br, I] with a Rongalite-NaHCO₃ reagent in aqueous dipolar aprotic solvents, such as DMF or DMSO, has been investigated. The reaction gave sodium perfluorocarboxylates [CF₃(CF₂)_n-1CO₂Na, n = 2 ∼ 11] in 51 – 86 % yields, and these were transformed to the respective perfluorocarboxylic acids [CF₃(CF₂)_n−1CO₂H, n = 2 ∼ 11] by treatment with sulfuric acid. This provides a new method for the synthesis of perfluorocarboxylic acids.     

Force field studies of some trifluoromethyl- and trichloromethyl-mercury-II) compounds

Force constants of [Hg(CF₃)₂], [Hg(CCl₃)₂], [Hg(CF₃)X] (X = Cl, Br, or I) and [Hg(CCl₃)X] (X = Cl or Br) have been calculated using a valence force field and wavenumber data from solutions. The potential energy distributions show substantial mixing between the symmetrical stretching and umbrella deformation coordinates of the trihalomethyl groups. The high degree of mixing of HgC and HgX stretching coordinates in [Hg(CF₃)Br] and [Hg(CF₃)I] accounts for the discontinuous frequency and intensity trends in the [Hg(CF₃)X] series.The results are discussed in comparison with methylmercury and other trifluoromethyl systems.     

C(CF3)2OH → OCH(CF3)2 Isomerism in some sulfur and phosphorus compounds

The insertion of (CF₃)₂CO into the PH bond of Me_nH_3?nP yields Me_nH_2?nPC(CF₃)₂OH and Me_nH_1?nP[C(CF₃)₂OH]₂ (n=O, 1), respectively [1]. MeP[C(CF₃)₂OH]₂ rearranges giving the diphosphine [MePOCH(CF₃)₂]₂ and the phosphorane MeP[OCH(CF₃)₂]₄. Me₂PH reacts with (CF₃)₂CO forming several products, e.g. MePF[OCH(CF₃)₂]₂ and Me₂PPMe₂ [1]. The phosphines tBu(R)PH(R=Me, tBu), however, add (CF₃)₂CO giving rise to the phosphinites tBu(R)POCH(CF₃)₂, which furnish stable phosphonium salts upon treating with MeI. (CF₃)₂CO inserts into the SH bond of RSH to yield RSC(CF₃)₂OH (R=H,Me,Ph), which were reacted with MeI, too. Reacting SCl₂ with LiOCH(CF₃)₂ gives S[OCH(CF₃)₂]₂ which is oxidised by chlorine to the sulfurane ClS[OCH(CF₃)₂]₃ [2]. The sulfurane is able to transfer (CF₃)₂CHO groups to phosphorus (III) compounds, e.g. P[OCH(CF₃)₂]₃ and Me₃P yielding P[OCH(CF₃)₂]₅ and [Me₃POCH(CF₃)₂]⁺Cl^?. ClS[OCH(CF₃)₂]₃ gives a stable salt upon reaction with SbCl₅, like ClP[OCH(CF₃)₂]₄. The mechanisms for these reactions are discussed.     

Mössbauer spectroscopic studies on the products of [2]ferrocenophane with CF3COOH,CCl3COOH,CF3SO3H,CH3COOH and SbCl5

Reaction products of [2]ferrocenophane with CF₃COOH, CCl₃COOH, CF₃SO₃H and SbCl₅ were prepared. Mössbauer spectroscopic data and magnetic susceptibility measurements suggest the bond formation of Fe–H⁺ and Fe–Cl⁺, in which iron atoms are in a high-spin Fe/II/state.     

A variable temperature study of the 19-F N.M.R. spectra of some fluoroalkylhydroxylamines: Conformational changes at the nitrogen atom [1]

The fluoroalkylhydroxylamines (I) - (VII) have been examined by variable temperature 19-F n.m.r. spectroscopy, and free energies of activation obtained for the process which renders equivalent the fluorines of the CF₂N group in (I), and the trifluoromethyl groups of the (CF₃)₂CFN group in (IV), and of the trifluoromethyl groups of the (CF₃)₂N group nearest to the asymmetric carbon atom in (V) - (VII). The possible conformational processes at the nitrogen atom are discussed. Δ$\text{G}$^≠/kJ mol^-1 (I) (CF₃CF₂CF₂)₂NOCF₂CF₂CF₃ 72 ± 6 (II) CF₃CF₂CF₂N(CF₃)OCF₂CF₂CF₃ (III) CF₃CF₂CF₂N(CF₃)OCF₃ (IV) (CF₃)₂CFN(CF₃)OCF(CF₃)₂ 71 ± 4 (V) (CF₃)₂NOCH₂CHClON(CF₃)₂ 60 ± 4 (VI) (CF₃)₂NOCH₂CHFON(CF₃)₂ 59 ± 4 (VII) (CF₃)₂NOCF₂CHFON(CF₃)2 59 ± 4 The perfluorotrialkylhydroxylamines (II) - (IV) were prepared by photochemical reaction of a perfluoroalkyl iodide with a perfluoroalkyl nitroso compound.Since it was observed that some alkyl hydroxylamines show magnetic non-equivalence in their low temperature n.m.r. spectra [2,3] there has been a number of studies of conformational changes in such compounds. For cyclic derivations [4,5] it is generally agreed that the changes are associated with hindered inversion at the nitrogen atom, but for acyclic compounds these have been variously ascribed to hindered inversion at the nitrogen atom [6,7] and to restricted rotation about the N-O bond [8,9]. The former explanation has received theoretical justification [10].     

[6,6]‐Open and [6,6]‐Closed Isomers of C70(CF2): Synthesis,Electrochemical and Quantum Chemical Investigation

Novel difluoromethylenated [70]fullerene derivatives, C₇₀(CF₂)_n (n=1–3), were obtained by the reaction of C₇₀ with sodium difluorochloroacetate. Two major products, isomeric C₇₀(CF₂) mono‐adducts with [6,6]‐open and [6,6]‐closed configurations, were isolated and their homofullerene and methanofullerene structures were reliably determined by a variety of methods that included X‐ray analysis and high‐level spectroscopic techniques. The [6,6]‐open isomer of C₇₀(CF₂) constitutes the first homofullerene example of a non‐hetero [70]fullerene derivative in which functionalisation involves the most reactive bond in the polar region of the cage. Voltammetric estimation of the electron affinity of the C₇₀(CF₂) isomers showed that it is substantially higher for the [6,6]‐open isomer (the 70‐electron π‐conjugated system is retained) than the [6,6]‐closed form, the latter being similar to the electron affinity of pristine C₇₀. In situ ESR spectroelectrochemical investigation of the C₇₀(CF₂) radical anions and DFT calculations of the hyperfine coupling constants provide evidence for the first example of an inter‐conversion between the [6,6]‐closed and [6,6]‐open forms of a cage‐modified fullerene driven by an electrochemical one‐electron transfer. Thus, [6,6]‐closed C₇₀(CF₂) constitutes an interesting example of a redox‐switchable fullerene derivative.     

The metathesis reactions of [SNS][SbF6] and [SN][AsF6] with Li[Al(OC(CF3)3)4] in liquid SO2

The small di- and triatomic molecules [SN]⁺ and [SNS]⁺ have shown versatile chemistries and [SNS]⁺ is an important starting reagent for many sulfur-nitrogen radicals. However, their chemistry is limited to the more polar solvents (e.g. SO₂). In this work an attempt is made to increase their solubility in less polar solvents by exchange of the usual [MF₆]⁻ (M = As, Sb) anions by the large and weakly coordinating [Al(OC(CF₃)₃)₄]⁻. As expected the metathesis reactions of [SN][AsF₆] and [SNS][SbF₆] with Li[Al(OC(CF₃)₃)₄] in liquid sulfur dioxide resulted in the formation of the insoluble Li[SbF₆], which is the driving force for these metathesis reactions. The characterization of the compounds by IR and multinuclear NMR revealed that [SNS]⁺ formed a [Al(OC(CF₃)₃)₄]⁻ salt in a clean reaction. A preliminary crystal structure of [SNS][Al(OC(CF₃)₃)₄] is presented. The solubility of [SNS][Al(OC(CF₃)₃)₄] in CH₂Cl₂ is significantly increased with respect to the corresponding [MF₆]⁻ salts, and potentially opens up new areas of [SNS]⁺ chemistry. The reaction of the more reactive [SN]⁺ with Li[Al(OC(CF₃)₃)₄] was less clear. Multinuclear NMR and IR spectra were consistent with the formation of [SN][Al(OC(CF₃)₃)₄], which also showed significant decomposition.