Synthesis,Characterization, and Application of Two Al(ORF)3 Lewis Superacids

We report herein the synthesis and full characterization of the donor‐free Lewis superacids Al(OR^F)₃ with OR^F=OC(CF₃)₃ ( 1 ) and OC(C₅F₁₀)C₆F₅ ( 2 ), the stabilization of 1 as adducts with the very weak Lewis bases PhF, 1,2‐F₂C₆H₄, and SO₂, as well as the internal C? F activation pathway of 1 leading to Al₂(F)(OR^F)₅ ( 4 ) and trimeric [FAl(OR^F)₂]₃ ( 5 , OR^F=OC(CF₃)₃). Insights have been gained from NMR studies, single‐crystal structure determinations, and DFT calculations. The usefulness of these Lewis acids for halide abstractions has been demonstrated by reactions with trityl chloride (NMR; crystal structures). The trityl salts allow the introduction of new, heteroleptic weakly coordinating [Cl‐Al(OR^F)₃]^? anions, for example, by hydride or alkyl abstraction reactions.     

Synthesis,Crystal Structure,and Physical Property of Sterically Unprotected Thiophene/Phenylene Co‐Oligomer Radical Cations: A Conductive π–π Bonded Supermolecular meso‐Helix

Sterically unprotected thiophene/phenylene co‐oligomer radical cation salts BPnT^.+[Al(OR_F)₄]^? (OR_F=OC(CF₃)₃, n=1–3) have been successfully synthesized. These newly synthesized salts have been characterized by UV/Vis‐NIR absorption and EPR spectroscopy, and single‐crystal X‐ray diffraction analysis. Their conductivity increases with chain length. The formed meso‐helical stacking by cross‐overlapping radical cations of BP2T^.+ is distinct from previously reported face‐to‐face overlaps of sterically protected (co‐)oligomer radical cations.     

Fluorination of alumino-silicate minerals: The example of lepidolite

The effect of fluorination on silicate and alumino-silicate minerals has been investigated, in particular on the lepidolite [K(Li,Al)₃ [Si₃AlO₁₀] (F,OH)₂] of the mica-type. The fluorination techniques included direct F₂-gas and cold radio-frequency-plasma involving c-C₄F₈ or O₂/CF₄ mixtures. The modifications of the surface properties have been followed mostly by XPS. Depending of the fluorination route used, either a reactive etching process involving M-F bonding occurs (direct F₂-gas; O₂-CF₄ rf-plasma), or a carbon fluoride deposition takes place (c-C₄F₈ rf-plasma).     

Snapshots of the Hydrolysis of the Lithium Alkoxide [Li{OC(CF3)3}]4

Exposure of the tetrameric, heterocubane‐like perfluorinated lithium alkoxide [Li{OC(CF₃)₃}]₄ to humid air gaverise to the hydrolysis products [{(CF₃)₃CO}Li(H₂O)₂‐μ‐(H₂O)‐Li(H₂O)₂{OC(CF₃)₃}], [{(CF₃)₃CO}Li(H₂O)₂‐μ‐(H₂O)‐Li‐(H₂O)₃]⁺[OC(CF₃)₃]^– and [Li(H₂O)₄]⁺[OC(CF₃)₃]^– because of stepwise addition of water molecules in a gas‐solid reaction without solvent. All compounds were studied by X‐ray crystallography and their solid‐state structures are strongly influenced by hydrogen bonding and fluorophilic interactions.     

A Systematic Investigation of Coinage Metal Carbonyl Complexes Stabilized by Fluorinated Alkoxy Aluminates

The reaction of Cu^I, Ag^I, and Au^I salts with carbon monoxide in the presence of weakly coordinating anions led to known and structurally unknown non‐classical coinage metal carbonyl complexes [M(CO)_n][A] (A=fluorinated alkoxy aluminates). The coinage metal carbonyl complexes [Cu(CO)_n(CH₂Cl₂)_m]⁺[A]^? (n=1, 3; m=4?n), [Au₂(CO)₂Cl]⁺[A]^?, [(OC)_nM(A)] (M=Cu: n=2; Ag: n=1, 2) as well as [(OC)₃Cu???ClAl(OR^F)₃] and [(OC)Au???ClAl(OR^F)₃] were analyzed with X‐ray diffraction and partially IR and Raman spectroscopy. In addition to these structures, crystallographic and spectroscopic evidence for the existence of the tetracarbonyl complex [Cu(CO)₄]⁺[Al(OR^F)₄]^? (R^F=C(CF₃)₃) is presented; its formation was analyzed with the help of theoretical investigations and Born–Fajans–Haber cycles. We discuss the limits of structure determinations by routine X‐ray diffraction methods with respect to the C? O bond lengths and apply the experimental CO stretching frequencies for the prediction of bond lengths within the carbonyl ligand based on a correlation with calculated data. Moreover, we provide a simple explanation for the reported, partly confusing and scattered CO stretching frequencies of [Cu^I(CO)_n] units.     

Facile access to the pnictocenium ions [Cp*ECl]+ (E = P, As) and [(Cp*)2P]+: chloride ion affinity of Al(OR(F))3

The pnictocenium salts [Cp*PCl]⁺[μCl]^? ( 1 a ), [Cp*PCl]⁺[ClAl(OR^F)₃]^? ( 1 b ), [Cp*AsCl]⁺[ClAl(OR^F)₃]^? ( 2 ), and [(Cp*)₂P]⁺[μCl]^? ( 3 ), in which Cp*=Me₅C₅, μCl=(^FRO)₃Al? Cl? Al(OR^F)₃, and OR^F=OC(CF₃)₃, were prepared by halide abstraction from the respective halopnictines with the Lewis superacid PhF→Al(OR^F)₃. 1 The X‐ray crystal structures of 1 a , 2 , and 3 established that in the half as well as in the sandwich cations the Cp* rings are attached in an η²‐fashion. By using one or two equivalents of the Lewis acid, the two new weakly coordinating anions [μCl]^? and [ClAl(OR^F)₃]^? resulted. They also stabilize the highly reactive cations in PhF or 1,2‐F₂C₆H₄ solution at room temperature. The chloride ion affinities (CIAs) of a range of classical strong Lewis acids were also investigated. The calculations are based on a set of isodesmic BP86/SV(P) reactions and a non‐isodesmic reference reaction assessed at the G3MP2 level.     

The Parent Cyclopentadienyltin Cation,Its Toluene Adduct,and the Quadruple‐Decker [Sn3Cp4]2+

Truly cationic metallocenes with the parent cyclopentadienyl ligand are so far unknown for the Group 14 elements. Herein we report on an almost “naked” [SnCp]⁺ cation with the weakly coordinating [Al{OC(CF₃)₃}₄]⁻ and [{(F₃C)₃CO}₃Al−F−Al{OC(CF₃)₃}₃]⁻ anions. [SnCp][Al{OC(CF₃)₃}₄] was used to prepare the first main‐group quadruple‐decker cation [Sn₃Cp₄]²⁺ again as the [Al{OC(CF₃)₃}₄]⁻ salt. Additionally, the toluene adduct [CpSn(C₇H₈)][Al{OC(CF₃)₃}₄] was obtained.     

The Parent Cyclopentadienyltin Cation,Its Toluene Adduct,and the Quadruple‐Decker [Sn3Cp4]2+

Truly cationic metallocenes with the parent cyclopentadienyl ligand are so far unknown for the Group 14 elements. Herein we report on an almost “naked” [SnCp]⁺ cation with the weakly coordinating [Al{OC(CF₃)₃}₄]⁻ and [{(F₃C)₃CO}₃Al−F−Al{OC(CF₃)₃}₃]⁻ anions. [SnCp][Al{OC(CF₃)₃}₄] was used to prepare the first main‐group quadruple‐decker cation [Sn₃Cp₄]²⁺ again as the [Al{OC(CF₃)₃}₄]⁻ salt. Additionally, the toluene adduct [CpSn(C₇H₈)][Al{OC(CF₃)₃}₄] was obtained.     

Homoleptic Gold Acetonitrile Complexes with Medium to Very Weakly Coordinating Counterions: Effect on Aurophilicity?

A series of gold acetonitrile complexes [Au(NCMe)₂]⁺[WCA]^? with weakly coordinating counterions (WCAs) was synthesized by the reaction of elemental gold and nitrosyl salts [NO]⁺[WCA]^? in acetonitrile ([WCA]^? = [GaCl₄]^?, [B(CF₃)₄]^?, [Al(OR^F)₄]^?; R^F = C(CF₃)₃). In the crystal structures, the [Au(NCMe)₂]⁺ units appeared as monomers, dimers, or chains. A clear correlation between the aurophilicity and the coordinating ability of counterions was observed, with more strongly coordinating WCAs leading to stronger aurophilic contacts (distances, C?N stretching frequencies of [Au(NCMe)₂]⁺ units). An attempt to prepare [Au(L)₂]⁺ units, even with less weakly basic solvents like CH₂Cl₂, led to decomposition of the [Al(OR^F)₄]^? anion and formation of [NO(CH₂Cl₂)₂]⁺[F(Al(OR^F)₃)₂]^?. All nitrosyl reagents [NO]⁺[WCA]^? were generated according to an optimized procedure and were thoroughly characterized by Raman and NMR spectroscopy. Moreover, the to date unknown species [NO]⁺[B(CF₃)₃CN]^? was prepared. Its reaction with gold unexpectedly produced [Au(NCMe)₂]⁺[Au(NCB(CF₃)₃)₂]^?, in which the cyanoborate counterion acts as an anionic ligand itself. Interestingly, the auroborate anion [Au(NCB(CF₃)₃)₂]^? behaves as a weakly coordinating counterion, which becomes evident from the crystallographic data and the vibrational spectral characteristics of the [Au(NCMe)₂]⁺ cation in this complex. Ligand exchange in the only room temperature stable salt of this series, [Au(NCMe)₂]⁺[Al(OR^F)₄]^?, is facile and, for example, [Au(PPh₃)(NCMe)]⁺[Al(OR^F)₄]^? can be selectively generated. This reactivity opens the possibility to generate various [AuL¹L²]⁺[Al(OR^F)₄]^? salts through consecutive ligand‐exchange reactions that offer access to a huge variety of Au^I complexes for gold catalysis.     

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.     

Synthesen und NMR‐Untersuchungen von Salzen mit den neuen Anionen [PtXn(CF3)6‐n]2— (n = 0 ‐ 5, X = F,OH, Cl,CN) und die Kristallstrukturanalyse von K2[(CF3)2F2Pt(μ‐OH)2PtF2(CF3)2]·2H2O

Syntheses and NMR Spectroscopic Ivestigations of Salts containing the Novel Anions [PtX_n(CF₃)_6‐n]^2— (n = 0 ‐ 5, X = F, OH, Cl, CN) and Crystal Structure of K₂[(CF₃)₂F₂Pt(μ‐OH)₂PtF₂(CF₃)₂]·2H₂O The first syntheses of trifluoromethyl‐complexes of platinum through fluorination of cyanoplatinates are reported. The fluorination of tetracyanoplatinates(II), K₂[Pt(CN)₄], and hexacyanoplatinates(IV), K₂[Pt(CN)₆], with ClF in anhydrous HF leads after working up of the products to K₂[(CF₃)₂F₂Pt(μ‐OH)₂PtF₂(CF₃)₂]·2H₂O. The structure of the salt is determined by a X‐ray structure analysis, P2₁/c (Nr. 14), a = 11.391(2), b = 11.565(2), c = 13.391(3)Å, β = 90.32(3)°, Z = 4, R₁ = 0.0326 (I > 2σ(I)). The reaction of [Bu₄N]₂[Pt(CN)₄] with ClF in CH₂Cl₂ generates mainly cis‐[Bu₄N]₂[PtCl₂(CF₃)₄] and fac‐[Bu₄N]₂[PtCl₃(CF₃)₃], but in contrast that of [Bu₄N]₂[Pt(CN)₆] with ClF in CH₂Cl₂ results cis‐[Bu₄N]₂[PtX₂(CF₃)₄], [Bu₄N]₂[PtX(CF₃)₅] (X = F, Cl) and [Bu₄N]₂[Pt(CF₃)₆]. In the products [Bu₄N]₂[PtX_n(CF₃)_6‐n] (X = F, Cl, n = 0—3) it is possibel to exchange the fluoro‐ligands into chloro‐ and cyano‐ligands by treatment with (CH₃)₃SiCl und (CH₃)₃SiCN at 50 °C. With continuing warming the trifluoromethyl‐ligands are exchanged by chloro‐ and cyano‐ligands, while as intermediates CF₂Cl and CF₂CN ligands are formed. The identity of the new trifluoromethyl‐platinates is proved by ¹⁹⁵Pt‐ and ¹⁹F‐NMR‐spectroscopy.     

Trifluoromethylation of carbon and boron with CF3SiMe3/NMe4F: formation of NMe4[trans-CF3CFCFB(CF3)3]

Trimethylamine-trifluoroethenyl-bis(trifluoromethyl)borane [F₂CCF(CF₃)₂B·NMe₃] (1) reacts with NMe₄[(CF₃)₂SiMe₃] in THF solution to form trimethylamine-bis(trifluoromethyl)pentafluoropropenylborane [trans-CF₃CFCF(CF₃)₂B·NMe₃] (3), the fluoroborate NMe₄[trans-CF₃CFCF(CF₃)₂BF] (4), the novel borates NMe₄[trans-CF₃CFCFB(CF₃)₃] (5) and NMe₄[cyclo-(CF₃)₂BCF₂CFCF₂CF₃] (6).     

Preparation and structural investigations of fluorinated tungsten(vi) alkoxides

The preparation and characterization of compounds of composition Cl_6-xW(OCH₂CF₃)_x (x = 1−6) and X₄W[OC(CH₃) (CF₃)₂]₂ (X = Cl,F) together with ¹⁹F NMR spectra are reported. An X-ray structure analysis of Cl₄W[OC(CH₃)(CF₃)₂]₂ shows a W-O-C angle of 173.6°, which is unusually large for metal alkoxides, and a short W-O distance of 181.9 pm. A discussion on structural aspects and a comparison with related tungsten-nitrogen compounds are presented. Cl₄W[OC(CH₃) (CF₃)₂]₂ is monoclinic, space group C2/m, with a = 820.3(2), b = 1059.2(2), c = 1071.6(2) pm, β = 99.72(2)°, Z = 2 and was refined to R = 0.031 for 848 observed reflections.     

The syntheses and mass spectra of P[CCCF3]3, As[CCCF3]3, and Sb[CCCF3]3

The syntheses of P[CCCF₃]₃, As[CC CF₃]₃, and Sb[CCCF₃]₃ are reported. The compounds are colorless and volatile, with melting points of ?20° to ?25°, 23–24°, and 55–56°C, respectively. The mass spectra show the molecular ion of each compound. The rearrangement ion [F₃CCCCCCF₂]⁺] gives the strongest peak in each spectrum.     

Silver–Ethene Complexes [Ag(η2‐C2H4)n][Al(ORF)4] with n=1, 2, 3 (RF=Fluorine‐Substituted Group)

Compounds including the free or coordinated gas‐phase cations [Ag(η²‐C₂H₄)_n]⁺ (n=1–3) were stabilized with very weakly coordinating anions [A]^? (A=Al{OC(CH₃)(CF₃)₂}₄, n=1 ( 1 ); Al{OC(H)(CF₃)₂}₄, n=2 ( 3 ); Al{OC(CF₃)₃}₄, n=3 ( 5 ); {(F₃C)₃CO}₃Al‐F‐Al{OC(CF₃)₃}₃, n=3 ( 6 )). They were prepared by reaction of the respective silver(I) salts with stoichiometric amounts of ethene in CH₂Cl₂ solution. As a reference we also prepared the isobutene complex [(Me₂C?CH₂)Ag(Al{OC(CH₃)(CF₃)₂}₄)] ( 2 ). The compounds were characterized by multinuclear solution‐NMR, solid‐state MAS‐NMR, IR and Raman spectroscopy as well as by their single crystal X‐ray structures. MAS‐NMR spectroscopy shows that the [Ag(η²‐C₂H₄)₃]⁺ cation in its [Al{OC(CF₃)₃}₄]^? salt exhibits time‐averaged D_3h‐symmetry and freely rotates around its principal z‐axis in the solid state. All routine X‐ray structures (2θ_max.<55°) converged within the 3σ limit at C?C double bond lengths that were shorter or similar to that of free ethene. In contrast, the respective Raman active C?C stretching modes indicated red‐shifts of 38 to 45 cm^?1, suggesting a slight C?C bond elongation. This mismatch is owed to residual librational motion at 100 K, the temperature of the data collection, as well as the lack of high angular data owing to the anisotropic electron distribution in the ethene molecule. Therefore, a method for the extraction of the C?C distance in [M(C₂H₄)] complexes from experimental Raman data was developed and meaningful C?C distances were obtained. These spectroscopic C?C distances compare well to newly collected X‐ray data obtained at high resolution (2θ_max.=100°) and low temperature (100 K). To complement the experimental data as well as to obtain further insight into bond formation, the complexes with up to three ligands were studied theoretically. The calculations were performed with DFT (BP86/TZVPP, PBE0/TZVPP), MP2/TZVPP and partly CCSD(T)/AUG‐cc‐pVTZ methods. In most cases several isomers were considered. Additionally, [M(C₂H₄)₃] (M=Cu⁺, Ag⁺, Au⁺, Ni⁰, Pd⁰, Pt⁰, Na⁺) were investigated with AIM theory to substantiate the preference for a planar conformation and to estimate the importance of σ donation and π back donation. Comparing the group 10 and 11 analogues, we find that the lack of π back bonding in the group 11 cations is almost compensated by increased σ donation.     

Synthesis of highly branched perfluoroethers by direct fluorination,promising new materials based on the hexafluoroacetone–ethylene copolymer

Direct fluorination of the hexafluoroacetone-ethylene copolymer, [CH₂CH₂OC(CF₃)₂]_n, under conditions designed to promote fragmentation of the polymer chain has led to the synthesis of a number of structurally unusual branched perfluoropolyethers [? CF₂? CF₂? O-C(CF₃)₂? ]_n. These new perfluoropolyethers have been characterized by ¹⁹F-NMR, and their physical properties are reported. Direct fluorination under milder conditions yields a high-molecular-weight perfluoropolyether.     

Darstellung und Kristallstruktur von (n-Bu4N)3[Ir(NCS)(SCN)5]

Preparation and Crystal Structure of (n-Bu₄N)₃[Ir(NCS)(SCN)₅] The evaporated ethanolic extrakt of the reaction product of K₃[IrCl₆] and HNO₃, refluxed with an aqueous KSCN solution yields a mixture of the linkage isomers [Ir(NCS)_n(SCN)_6?-n]^3?, n = 0? 2, and small amounts of linkage isomeric chloropentarhodanoiridates(III), from which [Ir(NCS)(SCN)₅]^3? has been isolated by ion exchange chromatography on DEAE-cellulose. The X-Ray structure determination on a single crystal of (n-Bu₄N)₃[Ir(NCS)(SCN)₅] (monoclinic, space group P 2₁/a, a = 17.513(5), b = 32.607(5), c = 23.661(5) Å, β = 94.757(5)°, Z = 8) confirms the existance of a heteroleptic hexakis(thiocyanato(N)-thiocyanato(S))iridate(III) with an Ir? N distance of 2.03 Å and Ir? S bond lengths between 2.29 and 2.38 Å. The SCN groups with angles between 166 and 175° are nearly linear with Ir? S? C angles from 99.9 to 109.4°. The Ir? N? C angles of the two crystallographic independent anions are 166 and 174°.     

Perfluormethyl-Element-Liganden. XVIII. Darstellung und spektroskopische Untersuchung von M(CO)5L und M(CO)4L2-Komplexen [L = MenP(CF3)3−n; n = 0–3; M = Cr,Mo, W]

Perfluoromethyl-Element-Ligands. XVIII. Preparation and Spectroscopic Investigation of M(CO)₅L and M(CO)₄L₂ Complexes [L = Me_nP(CF₃)_3?n; n = 0–3; M = Cr, Mo, W] M(CO)₅L and cis-M(CO)₄L₂ complexes, respectively [M = Cr, Mo, W; L = Me_nP(CF₃)_3?n; n = 0–3] are prepared reacting M(CO)₅ · THF or M(CO)₄norbor with L at room temperature. The cis-compounds isomerize above 50°C yielding the trans-complexes; the rate of isomerization increases with increasing number of CF₃ groups. Thermal reaction of M(CO)₆ (M = Cr, Mo, W) with P(CF₃)₃ yields M(CO)₅P(CF₃)₃ and trans-M(CO)₄[P(CF₃)₃]₂. Introduction of three P(CF₃)₃ ligands by reaction with M(CO)₃(cycloheptatriene) (M = Cr, Mo) proves unsuccessful; besides little M(CO)₅P(CF₃)₃ trans-M(CO)₄[P(CF₃)₃]₂ is formed. The new compounds are characterized by analytical and spectroscopic (n.m.r., i.r., MS) methods.     

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.     

Synthesis and Structural Characterization of Gallium(I) and Indium(I) Cations Coordinated by Pentamethylethylenediamine

Herein we report on the facile access to a Ga^I and In^I complex salt of pentamethyldiethylenetriamine (PMDTA) with the weakly coordinating counterion [Al(OR^F)₄]^– [R^F = C(CF₃)₃]. Thus, the low temperature reaction of [M(PhF)₂]⁺ (M = Ga, In) solutions in 1,2-F₂C₆H₄ (oDFB) with PMDTA yielded the title compounds M(PMDTA)⁺[Al(OR^F)₄]^– (M = Ga 1 , in 2 ) in non-optimized yields. Both compounds are highly sensitive towards air and moisture, have a rather limited lifetime at room temperature, but were structurally characterized.