Elusive Antimony‐Centered Radical Cations: Isolation,Characterization, Crystal Structures,and Reactivity Studies

One‐electron oxidation of the stibines Aryl₃Sb ( 1 , Aryl=2,6‐ⁱ Pr₂‐4‐OMe‐C₆H₂; 2 , Aryl=2,4,6‐ⁱ Pr₃‐C₆H₂) with AgSbF₆ and NaBAryl^F₄ (Aryl^F=3,5‐(CF₃)₂C₆H₃) afforded the first structurally characterized examples of antimony‐centered radical cations 1 ^.+[BAryl^F₄]⁻ and 2 ^.+[BAryl^F₄]⁻. Their molecular and electronic structures were investigated by single‐crystal X‐ray diffraction, electron paramagnetic resonance spectroscopy (EPR) and UV/Vis absorption spectroscopy, in conjunction with theoretical calculations. Moreover, their reactivity was investigated. The reaction of 2 ^.+[BAryl^F₄]⁻ and p ‐benzoquinone afforded a dinuclear antimony dication salt 3 ²⁺[BAryl^F₄]₂⁻, which was characterized by NMR spectroscopy and X‐ray diffraction analysis. The formation of the dication 3 ²⁺ further confirms that the isolated stibine radical cations are antimony‐centered.     

Elusive Antimony‐Centered Radical Cations: Isolation,Characterization, Crystal Structures,and Reactivity Studies

One‐electron oxidation of the stibines Aryl₃Sb ( 1 , Aryl=2,6‐ⁱ Pr₂‐4‐OMe‐C₆H₂; 2 , Aryl=2,4,6‐ⁱ Pr₃‐C₆H₂) with AgSbF₆ and NaBAryl^F₄ (Aryl^F=3,5‐(CF₃)₂C₆H₃) afforded the first structurally characterized examples of antimony‐centered radical cations 1 ^.+[BAryl^F₄]⁻ and 2 ^.+[BAryl^F₄]⁻. Their molecular and electronic structures were investigated by single‐crystal X‐ray diffraction, electron paramagnetic resonance spectroscopy (EPR) and UV/Vis absorption spectroscopy, in conjunction with theoretical calculations. Moreover, their reactivity was investigated. The reaction of 2 ^.+[BAryl^F₄]⁻ and p ‐benzoquinone afforded a dinuclear antimony dication salt 3 ²⁺[BAryl^F₄]₂⁻, which was characterized by NMR spectroscopy and X‐ray diffraction analysis. The formation of the dication 3 ²⁺ further confirms that the isolated stibine radical cations are antimony‐centered.     

Strengthening of the C−F Bond in Fumaryl Fluoride with Superacids

The reaction of fumaryl fluoride with the superacidic solutions XF/MF₅ (X=H, D; M=As, Sb) results in the formation of the monoprotonated and diprotonated species, dependent on the stoichiometric ratio of the Lewis acid to fumaryl fluoride. The salts [C₄H₃F₂O₂]⁺[MF₆]⁻ (M=As, Sb) and [C₄H₂X₂F₂O₂]²⁺([MF₆]⁻)₂ (X=H, D; M=As, Sb) are the first examples with a protonated acyl fluoride moiety. They were characterized by low-temperature vibrational spectroscopy. Low-temperature NMR spectroscopy and single-crystal X-ray structure analyses were carried out for [C₄H₃F₂O₂]⁺[SbF₆]⁻ as well as for [C₄H₄F₂O₂]²⁺([MF₆]⁻)₂ (M=As, Sb). The experimental results are discussed together with quantum chemical calculations of the cations [C₄H₄F₂O₂ ⋅ 2 HF]²⁺ and [C₄H₃F₂O₂ ⋅ HF]⁺ at the B3LYP/aug-cc-pVTZ level of theory. In addition, electrostatic potential (ESP) maps combined with natural population analysis (NPA) charges were calculated in order to investigate the electron distribution and the charge-related properties of the diprotonated species. The C−F bond lengths in the protonated dication are considerably reduced on account of the +R effect.     

Complexation and Versatile Reactivity of a Highly Lewis Acidic Cationic Mg Complex with Alkynes and Phosphines

[(BDI)Mg⁺][B(C₆F₅)₄⁻] ( 1 ; BDI=CH[C(CH₃)NDipp]₂; Dipp=2,6-diisopropylphenyl) was prepared by reaction of (BDI)MgnPr with [Ph₃C⁺][B(C₆F₅)₄⁻]. Addition of 3-hexyne gave [(BDI)Mg⁺ ⋅ (EtC≡CEt)][B(C₆F₅)₄⁻]. Single-crystal X-ray analysis, NMR investigations, Raman spectra, and DFT calculations indicate a significant Mg-alkyne interaction. Addition of the terminal alkynes PhC≡CH or Me₃SiC≡CH led to alkyne deprotonation by the BDI ligand to give [(BDI-H)Mg⁺(C≡CPh)]₂ ⋅ 2 [B(C₆F₅)₄⁻] ( 2 , 70 %) and [(BDI-H)Mg⁺(C≡CSiMe₃)]₂ ⋅ 2 [B(C₆F₅)₄⁻] ( 3 , 63 %). Addition of internal alkynes PhC≡CPh or PhC≡CMe led to [4+2] cycloadditions with the BDI ligand to give {Mg⁺C(Ph)=C(Ph)C[C(Me)=NDipp]₂}₂ ⋅ 2 [B(C₆F₅)₄⁻] ( 4 , 53 %) and {Mg⁺C(Ph)=C(Me)C[C(Me)=NDipp]₂}₂ ⋅ 2 [B(C₆F₅)₄⁻] ( 5 , 73 %), in which the Mg center is N,N,C-chelated. The (BDI)Mg⁺ cation can be viewed as an intramolecular frustrated Lewis pair (FLP) with a Lewis acidic site (Mg) and a Lewis (or Brønsted) basic site (BDI). Reaction of [(BDI)Mg⁺][B(C₆F₅)₄⁻] ( 1 ) with a range of phosphines varying in bulk and donor strength generated [(BDI)Mg⁺ ⋅ PPh₃][B(C₆F₅)₄⁻] ( 6 ), [(BDI)Mg⁺ ⋅ PCy₃][B(C₆F₅)₄⁻] ( 7 ), and [(BDI)Mg⁺ ⋅ PtBu₃][B(C₆F₅)₄⁻] ( 8 ). The bulkier phosphine PMes₃ (Mes=mesityl) did not show any interaction. Combinations of [(BDI)Mg⁺][B(C₆F₅)₄⁻] and phosphines did not result in addition to the triple bond in 3-hexyne, but during the screening process it was discovered that the cationic magnesium complex catalyzes the hydrophosphination of PhC≡CH with HPPh₂, for which an FLP-type mechanism is tentatively proposed.     

Aluminum(III) Cations [(NHC) ⋅ AlMes2]+: Synthesis,Characterization, and Application in FLP-Chemistry

The three-coordinate aluminum cations ligated by N-heterocyclic carbenes (NHCs) [(NHC) ⋅ AlMes₂]⁺[B(C₆F₅)₄]⁻ (NHC=IMe^Me 4 , IiPr^Me 5 , IiPr 6 , Mes=2,4,6-trimethylphenyl) were prepared via hydride abstraction of the alanes (NHC) ⋅ AlHMes₂ (NHC=IMe^Me 1 , IiPr^Me 2 , IiPr 3 ) using [Ph₃C]⁺[B(C₆F₅)₄]⁻ in toluene as hydride acceptor. If this reaction was performed in diethyl ether, the corresponding four-coordinate aluminum etherate cations [(NHC) ⋅ AlMes₂(OEt₂)]⁺ [B(C₆F₅)₄]⁻ 7 – 9 (NHC=IMe^Me 7 , IiPr^Me 8 , IiPr 9 ) were isolated. According to a theoretical and experimental assessment of the Lewis-acidity of the [(IMe^Me) ⋅ AlMes₂]⁺ cation is the acidity larger than that of B(C₆F₅)₃ and of similar magnitude as reported for Al(C₆F₅)₃. The reaction of [(IMe^Me) ⋅ AlMes₂]⁺[B(C₆F₅)₄]⁻ 4 with the sterically less demanding, basic phosphine PMe₃ afforded a mixed NHC/phosphine stabilized cation [(IMe^Me) ⋅ AlMes₂(PMe₃)]⁺[B(C₆F₅)₄]⁻ 10 . Equimolar mixtures of 4 and the sterically more demanding PCy₃ gave a frustrated Lewis-pair (FLP), i.e., [(IMe^Me) ⋅ AlMes₂]⁺[B(C₆F₅)₄]⁻/PCy₃ FLP-11 , which reacts with small molecules such as CO₂, ethene, and 2-butyne.     

Donor-Stabilised [SbF4]+: SbF5 as a Fluoride-Ion Donor

Antimony pentafluoride is a strong Lewis acid and fluoride-ion acceptor that has not previously demonstrated any discreet fluoride-ion donor properties. The first donor-stabilised [SbF₄]⁺ cations were prepared from the autoionisation of SbF₅ in the presence of bidentate N-donor ligands 2,2’-bipyridine (bipy) and 1,10-phenanthroline (phen) as their [SbF₆]⁻ salts. The [SbF₄(N−N)][Sb₂F₁₁] (N−N=bipy, phen) salts were synthesised by the addition of one equivalent of SbF₅⋅SO₂ to [SbF₄(N−N)][SbF₆] in liquid SO_2. The salts show remarkable stability and were characterised by Raman spectroscopy and multinuclear NMR spectroscopy. The crystal structures of [SbF₄(phen)][SbF₆] ⋅ 3CH₃CN and [SbF₄(phen)][SbF₆] ⋅ 2SO₂ were determined, showing distorted octahedral cations. DFT calculations and NBO analyses reveal that significant degree of electron-pair donation from N to Sb stabilizes [SbF₄]⁺ with the Sb−N bond strength being approximately two thirds of that of the Sb−F bonds in these cations and the cationic charge being primarily ligand-centred.     

Syntheses,Structures, and Bonding of NgF2⋅CrOF4, NgF2⋅2CrOF4 (Ng=Kr,Xe), and (CrOF4)∞

The noble-gas difluoride adducts, NgF₂ ⋅ CrOF₄ and NgF₂ ⋅ 2CrOF₄ (Ng=Kr and Xe), have been synthesized and structurally characterized at low temperatures by Raman spectroscopy and single-crystal X-ray diffraction. The low fluoride ion affinity of CrOF₄ renders it incapable of inducing fluoride ion transfer from NgF₂ (Ng=Kr and Xe) to form ion-paired salts of the [NgF]⁺ cations having either the [CrOF₅]⁻ or [Cr₂O₂F₉]⁻ anions. The crystal structures show the NgF₂ ⋅ CrOF₄ adducts are comprised of F_t−Ng−F_b- - -Cr(O)F₄ structural units in which NgF₂ is weakly coordinated to CrOF₄ by means of a fluorine bridge, F_b, in which Ng−F_b is elongated relative to the terminal Ng−F_t bond. In contrast with XeF₂ ⋅ 2MOF₄ (M=Mo or W) and KrF₂ ⋅ 2MoOF₄, in which the Lewis acidic, F₄(O)M- - -F_b- - -M(O)F₃ moiety coordinates to Ng through a single M- - -F_b−Ng bridge, both fluorine ligands of NgF₂ coordinate to CrOF₄ molecules to form F₄(O)Cr- - -F_b−Ng−F_b- - -Cr(O)F₄ adducts in which both Ng−F_b bonds are only marginally elongated relative to the Ng−F bonds of free NgF₂. Quantum-chemical calculations show that the Cr−F_b bonds of NgF₂ ⋅ CrOF₄ and NgF₂ ⋅ 2CrOF₄ are predominantly electrostatic with a small degree of covalent character that accounts for their nonlinear Cr- - -F_b−Ng bridge angles and staggered O−Cr- - -F_b−Ng−F_t dihedral angles. The crystal structures and Raman spectra of two CrOF₄ polymorphs have also been obtained. Both are comprised of fluorine-bridged chains that are cis- and trans-fluorine-bridged with respect to oxygen.     

An Isolable Radical Anion Featuring a 2-Center-3-Electron π-Bond without a Clearly Defined σ-Bond

Featuring an extra electron in the π* antibonding orbital, species with a 2-center-3-electron (2c3e) π bond without an underlying σ bond are scarcely known. Herein, we report the synthesis, isolation and characterization of a radical anion salt [K(18-C-6)]⁺{[(HCNDipp)₂Si]₂P₂}⋅⁻ (i.e. [K(18-C-6)]⁺ 3 ⋅⁻) (18-C-6=18-crown-6, Dipp=2,6-diisopropylphenyl), in which 3 ⋅⁻ features a perfectly planar Si₂P₂ four-membered ring. This species represents the first example of a Si- and P-containing analog of a bicyclo[1.1.0]butane radical anion. The unusual bonding motif of 3 ⋅⁻ was thoroughly investigated via X-ray diffraction crystallography, electron paramagnetic resonance spectroscopy (EPR), and calculations by density functional theory (DFT), which collectively unveiled the existence of a 2c3e π bond between the bridgehead P atoms and no clearly defined supporting P−P σ bond.     

Competitive Coordination of Chloride and Fluoride Anions Towards Trivalent Lanthanide Cations (La3+ and Nd3+) in Molten Salts

Molten salt electrolysis is a vital technique to produce high-purity lanthanide metals and alloys. However, the coordination environments of lanthanides in molten salts, which heavily affect the related redox potential and electrochemical properties, have not been well elucidated. Here, the competitive coordination of chloride and fluoride anions towards lanthanide cations (La³⁺ and Nd³⁺) is explored in molten LiCl-KCl-LiF-LnCl₃ salts using electrochemical, spectroscopic, and computational approaches. Electrochemical analyses show that significant negative shifts in the reduction potential of Ln³⁺ occur when F⁻ concentration increases, indicating that the F⁻ anions interact with Ln³⁺ via substituting the coordinated Cl⁻ anions, and confirm [LnCl_xF_y]^3−x−y (y_max=3) complexes are prevailing in molten salts. Spectroscopic and computational results on solution structures further reveal the competition between Cl⁻ and F⁻ anions, which leads to the formation of four distinct Ln(III) species: [LnCl₆]³⁻, [LnCl₅F]³⁻, [LnCl₄F₂]³⁻ and [LnCl₄F₃]⁴⁻. Among them, the seven-coordinated [LnCl₄F₃]⁴⁻ complex possesses a low-symmetry structure evidenced by the pattern change of Raman spectra. After comparing the polarizing power (Z/r) among different metal cations, it was concluded that Ln−F interaction is weaker than that between transition metal and F⁻ ions.     

Syntheses and Structures of 5-Membered Heterocycles Featuring 1,2-Diphospha-1,3-Butadiene and Its Radical Anion

LGa(P₂OC)cAAC 2 features a 1,2-diphospha-1,3-butadiene unit with a delocalized π-type HOMO and a π*-type LUMO according to DFT calculations. [LGa(P₂OC)cAAC][K(DB-18-c-6)] 3 [K(DB-18-c-6] containing the 1,2-diphospha-1,3-butadiene radical anion 3 ⋅ ⁻ was isolated from the reaction of 2 with KC₈ and dibenzo-18-crown-6. 3 reacted with [Fc][B(C₆F₅)₄] (Fc=ferrocenium) to 2 and with TEMPO to [L^−HGa(P₂OC)cAAC][K(DB-18-c-6)] 4 [K(DB-18-c-6] containing the 1,2-diphospha-1,3-butadiene anion 4⁻ . The solid state structures of 2 , 3 K(DB-18-c-6], and 4 [K(DB-18-c-6] were determined by single crystal X-ray diffraction (sc-XRD).     

Effect of Axial Ligands on Easy-Axis Anisotropy and Field-Induced Slow Magnetic Relaxation in Heptacoordinated FeII Complexes

A rational approach to modulating easy-axis magnetic anisotropy by varying the axial donor ligand in heptacoordinated Fe^II complexes has been explored. In this series of complexes with formulae of [Fe(H₄L)(NCS)₂] ⋅ 3 DMF ⋅ 0.5 H₂O ( 1 ), [Fe(H₄L)(NCSe)₂] ⋅ 3 DMF ⋅ 0.5 H₂O ( 2 ), and [Fe(H₄L)(NCNCN)₂] ⋅ DMF ⋅ H₂O ( 3 ) [H₄L=2,2′-{pyridine-2,6-diylbis(ethan-1-yl-1-ylidene)}bis(N-phenylhydrazinecarboxamide)], the axial positions are successively occupied by different nitrogen-based π-donor ligands. Detailed dc and ac magnetic susceptibility measurements reveal the existence of easy-axis magnetic anisotropy for all of the complexes, with 1 [U_eff=21 K, τ₀=1.72×10⁻⁶ s] and 2 [U_eff=25 K, τ₀=2.25×10⁻⁶ s] showing field-induced slow magnetic relaxation behavior. However, both experimental studies and theoretical calculations indicate the magnitude of the D value of complex 3 to be larger than those of complexes 1 and 2 due to the axial bond angle being smaller than that for an ideal geometry. Detailed analysis of the field and temperature dependences of relaxation time for 1 and 2 has revealed that multiple relaxation processes (quantum tunneling of magnetization, direct, and Raman) are involved in slow magnetic relaxation for both of these complexes. Magnetic dilution experiments support the role of intermolecular short contacts.     

Crystal Growth and Crystal Structures of Gold(V) Compounds: Cu(AuF6)2, Ag(AuF6)2, and O2(CuF)3(AuF6)4 ⋅ HF

Crystal growth from anhydrous hydrogen fluoride solutions of M²⁺ (M=Cu, Ag) and [AuF₆]⁻ gave M(AuF₆)₂ salts (M=Cu, Ag). Similar attempts to prepare single crystals of the corresponding nickel, zinc and magnesium salts failed. The crystal structure of Cu(AuF₆)₂ consists of layers of Cu²⁺ cations connected by [AuF₆]⁻ anions, thus forming slabs. Only van der Waals interactions exist between adjacent slabs. The crystal structure of Ag(AuF₆)₂ consists of a three-dimensional framework in which Ag⁺ cations are linked by [AuF₆]⁻ anions. Both structures are members of the M^II(X^VF₆)₂ family, in which seven different structure types have been observed to date. In the crystal structure of O₂(CuF)₃(AuF₆)₄ ⋅ HF, the bridging AuF₆ units connect [−Cu−F−Cu−F−]_∞ chains to form stacks between which O₂⁺ cations and HF molecules are located.     

Porphyrinylphosphonate-Based Metal–Organic Framework: Tuning Proton Conductivity by Ligand Design

A novel metal–organic framework [Zn₃(Ni-H₂TPPP)(Ni-H₄TPPP)(Ni-H₅TPPP) ⋅ 7(CH₃)₂NH₂ ⋅ DMF ⋅ 7 H₂O] (where Ni-H_xTPPP (x=2,4,5) are partially deprotonated [5,10,15,20-tetrakis(3-(phosphonatophenyl)-porphyrinato(2-))]nickel(II) species), IPCE-2Ni , with outstanding proton conductivity (1.0×10⁻² S cm⁻¹ at 75 °C and 95 % relative humidity) has been obtained. The high concentration of free phosphonate groups and compensating dimethylammonium cations bound by hydrogen bonds in the unique crystal structure of IPCE-2Ni is a key factor responsible for the observed high proton conductivity, which is one order of magnitude higher than for the corresponding MOF based on 5,10,15,20-tetrakis(4-(phosphonatophenyl)porphyrinato(2-))]nickel(II) IPCE-1Ni and comparable with that of leaders among MOFs.     

Self-Assembly of Polyoxometalate-Resorcin[4]arene-Based Inorganic-Organic Complexes: Metal Ion Effects on the Electrochemical Performance of Lithium Ion Batteries

With their adjustable structures and diverse functions, polyoxometalate (POM)-resorcin[4]arene-based inorganic–organic complexes are a kind of potential multifunctional material. They have potential applications for lithium ion batteries (LIBs). However, the relationship between different coordinated metal ions and electrochemical performance has rarely been investigated. Here, three functionalized POM-resorcin[4]arene-based inorganic–organic materials, [Co₂(TMR4 A)₂(H₂O)₁₀][SiW₁₂O₄₀] ⋅ 2 EtOH ⋅ 4.5 H₂O ( 1 ), [Ni₂(TMR4 A)₂(H₂O)₁₀][SiW₁₂O₄₀] ⋅ 4 EtOH ⋅ 13 H₂O ( 2 ), and [Zn₂(TMR4 A)₂(H₂O)₁₀][SiW₁₂O₄₀] ⋅ 2 EtOH ⋅ 2 H₂O ( 3 ), have been synthesized. Furthermore, to enhance the conductivities of these compounds, 1–3 were doped with reduced graphene oxide (RGO) to give composites 1 @RGO- 3 @RGO, respectively. As anode materials for LIBs, 1 @RGO- 3 @RGO can deliver very high discharge capacities (1445.9, 1285.0 and 1095.3 mAh g⁻¹, respectively) in the initial run, and show discharge capacities of 898, 665 and 651 mAh g⁻¹, respectively, at a current density of 0.1 A g⁻¹ over 100 runs. More importantly, the discharge capacities of 319, 283 and 329 mAh g⁻¹ were maintained for 1 @RGO- 3 @RGO even after 400 cycles at large current density (1 A g⁻¹).     

Spin-Crossover Iron(II) Compounds with Pendent Tetraphenylethylene Group

Two iron(II) compounds with the general formula of [Fe(phen-TPE)₂(NCX)₂] ⋅ Y (phen-TPE=3-(tetraphenylethylene)-1,10-phenanthroline; X=S and Y=2DMF for 1 ⋅ 2DMF ; X=Se and Y=DMF for 2 ⋅ DMF ) were synthesized and characterized by single-crystal X-ray crystallography and magnetic measurements. Both compounds exhibited thermal-induced complete one-step spin-crossover (SCO) behavior with the critical transition temperatures of 210 K and 260 K for 1 ⋅ 2DMF and 2 ⋅ DMF , respectively. The SCO behavior of these two isomorphic compounds depended significantly on robust intermolecular π⋅⋅⋅π interactions, NCX⁻ groups and solvent molecules.     

Pseudohalogen Chemistry in Ionic Liquids with Non-innocent Cations and Anions

Within the second funding period of the SPP 1708 “Material Synthesis near Room Temperature”,which started in 2017, we were able to synthesize novel anionic species utilizing Ionic Liquids (ILs) both, as reaction media and reactant. ILs, bearing the decomposable and non-innocent methyl carbonate anion [CO₃Me]⁻, served as starting material and enabled facile access to pseudohalide salts by reaction with Me₃Si−X (X=CN, N₃, OCN, SCN). Starting with the synthesized Room temperature Ionic Liquid (RT-IL) [nBu₃MeN][B(OMe)₃(CN)], we were able to crystallize the double salt [nBu₃MeN]₂[B(OMe)₃(CN)](CN). Furthermore, we studied the reaction of [WCC]SCN and [WCC]CN (WCC=weakly coordinating cation) with their corresponding protic acids HX (X=SCN, CN), which resulted in formation of [H(NCS)₂]⁻ and the temperature labile solvate anions [CN(HCN)_n]⁻ (n=2, 3). In addition, the highly labile anionic HCN solvates were obtained from [PPN]X ([PPN]=μ-nitridobis(triphenylphosphonium), X=N₃, OCN, SCN and OCP) and HCN. Crystals of [PPN][X(HCN)₃] (X=N₃, OCN) and [PPN][SCN(HCN)₂] were obtained when the crystallization was carried out at low temperatures. Interestingly, reaction of [PPN]OCP with HCN was noticed, which led to the formation of [P(CN)₂]⁻, crystallizing as HCN disolvate [PPN][P(CN⋅HCN)₂]. Furthermore, we were able to isolate the novel cyanido(halido) silicate dianions of the type [SiCl_0.78(CN)_5.22]²⁻ and [SiF(CN)₅]²⁻ and the hexa-substituted [Si(CN)₆]²⁻ by temperature controlled halide/cyanide exchange reactions. By facile neutralization reactions with the non-innocent cation of [Et₃HN]₂[Si(CN)₆] with MOH (M=Li, K), Li₂[Si(CN)₆] ⋅ 2 H₂O and K₂[Si(CN)₆] were obtained, which form three dimensional coordination polymers. From salt metathesis processes of M₂[Si(CN)₆] with different imidazolium bromides, we were able to isolate new imidazolium salts and the ionic liquid [BMIm]₂[Si(CN)₆]. When reacting [Mes(nBu)Im]₂[Si(CN)₆] with an excess of the strong Lewis acid B(C₆F₅)₃, the voluminous adduct anion {Si[CN⋅B(C₆F₅)₃]₆}²⁻ was obtained.     

One- and Two-Electron Transfer Oxidation of 1,4-Disilabenzene with Formation of Stable Radical Cations and Dications

Electron-transferable oxidants such as B(C₆F₅)₃/nBuLi, B(C₆F₅)₃/LiB(C₆F₅)₄, B(C₆F₅)₃/LiHBEt₃, Al(C₆F₅)₃/(o-RC₆H₄)AlH₂ (R=N(CMe₂CH₂)₂CH₂), B(C₆F₅)₃/AlEt₃, Al(C₆F₅)₃, Al(C₆F₅)₃/nBuLi, Al(C₆F₅)₃/AlMe₃, (CuC₆F₅)₄, and Ag₂SO₄, respectively were employed for reactions with (L)₂Si₂C₄(SiMe₃)₂(C₂SiMe₃)₂ (L=PhC(NtBu)₂, 1 ). The stable radical cation [ 1 ]^+. was formed and paired with the anions [nBuB(C₆F₅)₃]⁻ (in 2 ), [B(C₆F₅)₄]⁻ (in 3 ), [HB(C₆F₅)₃]⁻ (in 4 ), [EtB(C₆F₅)₃]⁻ (in 5 ), {[(C₆F₅)₃Al]₂(μ-F)]⁻ (in 6 ), [nBuAl(C₆F₅)₃]⁻ (in 7 ), and [Cu(C₆F₅)₂]⁻ (in 8 ), respectively. The stable dication [ 1 ]²⁺ was also generated with the anions [EtB(C₆F₅)₃]⁻ ( 9 ) and [MeAl(C₆F₅)₃]⁻ ( 10 ), respectively. In addition, the neutral compound [(L)₂Si₂C₄(SiMe₃)₂(C₂SiMe₃)₂][μ-O₂S(O)₂] ( 11 ) was obtained. Compounds 2 – 11 are characterized by UV-vis absorption spectroscopy, X-ray crystallography, and elemental analysis. Compounds 2 – 8 are analyzed by EPR spectroscopy and compounds 9 – 11 by NMR spectroscopy. The structure features are discussed on the central Si₂C₄-rings of 1 , [ 1 ]^+., [ 1 ]²⁺, and 11 , respectively.     

Preparation and Structural Characterization of [CpRu(1,10-phenanthroline)(CH3CN)][X] and Precursor Complexes (X=PF6, BArF,TRISPHAT-N)

Cationic [Ru(η⁵-C₅H₅)(CH₃CN)₃]⁺ complex, tris(acetonitrile)(cyclopentadienyl)ruthenium(II), gives rise to a very rich organometallic chemistry. Combined with diimine ligands, and 1,10-phenanthroline in particular, this system efficiently catalyzes diazo decomposition processes to generate metal-carbenes which undergo a series of original transformations in the presence of Lewis basic substrates. Herein, syntheses and characterizations of [CpRu(Phen)(L)] complexes with (large) lipophilic non-coordinating (PF₆⁻ and BAr_F⁻) and coordinating TRISPHAT-N⁻ anions are reported. Complex [CpRu(η⁶-naphthalene)][BAr_F] ( [1][BAr_F] ) is readily accessible, in high yield, by direct counterion exchange between [1][PF₆] and sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBAr_F) salts. Ligand exchange of [1][BAr_F] in acetonitrile generated stable [Ru(η⁵-C₅H₅)(CH₃CN)₃][BAr_F] ( [2][BAr_F] ) complex in high yield. Then, the desired [CpRu(Phen)(CH₃CN)] ( [3] ) complexes were obtained from either the [1] or [2] complex in the presence of the 1,10-phenanthroline as ligand. For characterization and comparison purposes, the anionic hemilabile ligand TRISPHAT−N (TTN) was introduced on the ruthenium center, from the complex [3][PF₆] , to quantitatively generate the desired complex [CpRu(Phen)(TTN)] ( [4] ) by displacement of the remaining acetonitrile ligand and of the PF₆⁻ anion. Solid state structures of complexes [1][BAr_F] , [2][BAr_F] , [3][BAr_F] , [3][PF₆] and [4] were determined by X-ray diffraction studies and are discussed herein.     

Chromium Oxide Tetrafluoride and Its Reactions with Xenon Hexafluoride; the [XeF5]+ and [Xe2F11]+ Salts of the [CrVIOF5]−, [CrVOF5]2−, [CrV2O2F8]2−, and [CrIVF6]2− Anions

Molten mixtures of XeF₆ and Cr^VIOF₄ react by means of F₂ elimination to form [XeF₅][Xe₂F₁₁][Cr^VOF₅] ⋅ 2 Cr^VIOF₄, [XeF₅]₂[Cr^IVF₆] ⋅ 2 Cr^VIOF₄, [Xe₂F₁₁]₂[Cr^IVF₆], and [XeF₅]₂[Cr^V₂O₂F₈], whereas their reactions in anhydrous hydrogen fluoride (aHF) and CFCl₃/aHF yield [XeF₅]₂[Cr^V₂O₂F₈] ⋅ 2 HF and [XeF₅]₂[Cr^V₂O₂F₈] ⋅ 2 XeOF₄. Other than [Xe₂F₁₁][M^VIOF₅] and [XeF₅][M^VI₂O₂F₉] (M=Mo or W), these salts are the only Group 6 oxyfluoro-anions known to stabilize noble-gas cations. Their reaction pathways involve redox transformations that give [XeF₅]⁺ and/or [Xe₂F₁₁]⁺ salts of the known [Cr^VOF₅]²⁻ and [Cr^IVF₆]²⁻ anions, and the novel [Cr^V₂O₂F₈]²⁻ anion. A low-temperature Raman spectroscopic study of an equimolar mixture of solid XeF₆ and CrOF₄ revealed that [Xe₂F₁₁][Cr^VIOF₅] is formed as a reaction intermediate. The salts were structurally characterized by LT single-crystal X-ray diffraction and LT Raman spectroscopy, and provide the first structural characterizations of the [Cr^VOF₅]²⁻ and [Cr^V₂O₂F₈]²⁻ anions, where [Cr^V₂O₂F₈]²⁻ represents a new structural motif among the known oxyfluoro-anions of Group 6. The X-ray structures show that [XeF₅]⁺ and [Xe₂F₁₁]⁺ form ion pairs with their respective anions by means of Xe- - -F–Cr bridges. Quantum-chemical calculations were carried out to obtain the energy-minimized, gas-phase geometries and the vibrational frequencies of the anions and their ion pairs and to aid in the assignments of their Raman spectra.     

Synthesis and Characterization of a Stable Nickelocenium Dication Salt

We report the synthesis and characterization of the nickelocenium cations [NiCp₂]⋅⁺ and [NiCp₂]²⁺ as their [F-{Al(OR^F)₃}₂]⁻ (Cp = C₅H₅; R^F=C(CF₃)₃) salts. Diamagnetic [NiCp₂]²⁺ represents the first example for the isolation of an unsubstituted parent metallocene dication. Both salts were generated by reacting neutral NiCp₂ with [NO]⁺[F-{Al(OR^F)₃}₂]⁻ in 1,2,3,4-tetrafluorobenzene (4FB). The salts were characterized by single crystal X-ray diffraction (XRD), indicating shorter metal-ligand bond lengths for the higher charged salt. Powder XRD shows the salts to be phase pure, cyclic voltammetry in 4FB gave quasi reversible redox waves at −0.44 (0→1) and +1.17 V (1→2) vs Fc/Fc⁺. The ¹H NMR of [NiCp₂]²⁺ is a singlet at 8.6 ppm, whereas paramagnetic [NiCp₂]⋅⁺ is significantly shifted upfield to −103.1 ppm.