Rapid Determination of Trifluoromethanesulfonate and p-Toluenesulfonate by Ion-Pair Chromatography Using a Reversed-Phase Silica-Based Monolithic Column: Application to the Analysis of Ionic Liquids

A method of ion-pair chromatography was developed on a reversed-phase silica-based monolithic column for the fast and simultaneous determination of trifluoromethanesulfonate (CF₃SO₃ ⁻) and p-toluenesulfonate (C₇H₇SO₃ ⁻). The analysis was performed using a mobile phase of tetrabutylammonium hydroxide + citric acid + acetonitrile on the Chromolith Speed ROD RP-18e column with direct conductivity detection. The effects of the eluent, column temperature and flow rate on the retention of the anions were investigated. The experimental phenomenon was discussed according to hydrophobic interaction and ion-exchange mechanism in the separation. The optimized chromatographic conditions were selected. The optimized eluent for the separation consisted of 0.2 mmol L⁻¹ tetrabutylammonium hydroxide + 0.10 mmol L⁻¹ citric acid + 9% acetonitrile (pH 5.5). The flow rate was set at 6.0 mL min⁻¹. The column temperature was 25 °C. Under the optimal conditions, the better separation of CF₃SO₃ ⁻ and C₇H₇SO₃ ⁻ was achieved without any interference by other anions (Cl⁻, Br⁻, I⁻, NO₃ ⁻, SO₄ ²⁻, ClO₃ ⁻, BF₄ ⁻ and PF₆ ⁻). The detection limit (S/N = 3) was 0.28 and 0.71 mg L⁻¹ for CF₃SO₃ ⁻ and C₇H₇SO₃ ⁻, respectively. The method has been applied to the determination of CF₃SO₃ ⁻ and C₇H₇SO₃ ⁻ in ionic liquids. The spiked recoveries of CF₃SO₃ ⁻ and C₇H₇SO₃ ⁻ were 101.1 and 100.2%, respectively.

     

Activity coefficients and pitzer parameters in the systems Na+/Cs+/Cl-/TcO 4 - or ClO 4 - /H2O at 25°C

Isopiestic vapor pressure experiments are performed at 25°C with aqueous NaTcO₄, mixed NaTcO₄-NaCl, and NaCl reference solutions. The solubility of CsTcO₄ is determined in 0–7.4m CsCl and in 0–5.6m NaCl solutions. The osmotic coefficients of the binary and ternary solutions are used to evaluate the binary Pitzer parameters Β⁰, Β^l, and C^Φ for NaTcO₄ and the mixing parameters θ_{TcO 4} ^- /cl^- and ψ_Na ⁺/TcO ₄ ^- /cl^-. The binary Pitzer parameters for the sparingly soluble CsTcO₄ and CsC1O₄ are calculated together with ψ_Cs ⁺/mo ₄ ^- /cl^- from their solubilities in CsCl solution. The solubilities of CsTcO₄ in NaCl and CsClO₄ in NaClO₄ solution are also included in the parametrization of the reciprocal salt systems Na⁺/Cs⁺/Cl^-/MO ₄ ^- . The parameters Β⁰ and Β^l of pertechnetate and perchlorate salts correlate well with the ionic radii.     

Carbon skeletal rearrangements in 2-phenylthiophene and 2,5-diphenylthiophene under conditions of electron-impact

The mass spectra of ¹³C-labelled 2-phenylthiophenes and 2,5-diphenylthiophenes were studied. The label distributions for the [HCS]⁺, [C₂H₂S]^+·, [C₈H₆]^+·, [C₉H₇]⁺ and [C₇H₅]S⁺ ions from 2-phenylthiophene and the [HCS]⁺, [C₉H₇]⁺, [C₇H₅S]^+·, and [C₁₅H₁₁]⁺ ions from 2,5-diphenylthiophene were interpreted in terms of both carbon skeletal rearrangements in the thiophene ring and migration of the phenyl substituent. The degree of carbon scrambling in the thiophene ring appeared to be almost independent of the electron beam energy. The formation of some of the fragment ions studied seems to be so fast that no carbon scrambling could be detected at all; in neither case was complete scrambling of the carbon atoms of the thiophene ring observed.     

Strukturdynamische organometall-komplexe: III. Synthese,struktur und bindungsverhältnisse der komplexe (η5-C5H5)Pd(η1-C5H5)PR3

The complexes (η₅-C₅H₅)Pd(η¹-C₅H₅)PR₃ which are prepared from [Cl(PR₃)-Pd]₂(μ-OCOCH₃)₂ and TlC₅H₅ are fluxional in solution. According to the ¹H and ¹³C NMR spectra at various temperatures, two dynamic processes occur. The process with the higher activation energy is a π/σ (η⁵/η¹) exchange of the two different cyclopentadienyl ligands, whereas the second one with the lower activation energy presumably is a metallotropic rearrangement (1,2-shift). The coalescence temperature for the η⁵/η¹ exchange depends on the size of the phosphine. The X-ray structural analysis of (C₅H₅)₂PdPPrⁱ₃ proves that it exists as a “frozen” η⁵ + η¹ structure in the crystal with the palladium approximately in a square-planar coordination. The η⁵-bonded cyclopentadienyl ring shows some unusual bonding patterns which are obviously electronic in nature. EHT-MO calculations for (η⁵-C₅H₅)PdCH₃(PH₃) indicate that in this model system alternating CC distances in the ring and a stronger bond of the metal to one of the five carbon atoms of the C₅H₅ ligand are to be expected. The calculations suggest that in similar complexes possessing a six-electron donor ligand like C₅H₅^? and a metal fragment which is isolobal to PdCH₃(PH₃)⁺, analogous distortions should be observed. Some reactions of the compounds (η⁵-C₅H₅)Pd(η¹-C₅H₅)PR₃ are described.     

The study of distribution coefficients of silver and mercury with chelating ion-exhange resin Dowex A-1

The distribution coefficients (DC) for HgCl ₄ ^2– , Hg(SO₄) ₂ ^2– , Hg(NO₃) ₄ ^2– , Ag⁺, Ag(SCN) ₂ ^– and Ag(NH₃) ₂ ⁺ between aqueous solutions and Dowex A-1 were measured in varying hydrogen ion concentrations. The DC of Ag⁺ in the NO ₃ ^– media was very low (4 to 6). The DC for the Ag(SCN) ₂ ^– complex decreased as pH increased. The Ag(NH₃) ₂ ⁺ complex had a constant DC of about 65 from pH 8 and above. The trend observed for three mercury complexes in HCl, H₂SO₄ and HNO₃ was similar; the DC decreased steadily from 0.1M to 6M. The HgCl ₄ ^2– complex had the highest DC (9000) while the Hg(NO₃) ₄ ^2– complex had the lowest DC (2000).     

Study on the extraction of U(IV) relevant to PUREX process

The paper presents a radiokinetic study on the appearance and growth of^*Fe₂S₃,^*Fe(OH)₃,^*Fe₂(C₂O₄)₃,^*Fe(IO₃)₃ crystals in a colloidal medium of agar and gelatine. The values of the diffusion constants through gels of⁵⁵⁺⁵⁹Fe³⁺ radioactive cations and of the rate of global growth process of these crystals in agar or gelatine were calculated using the experimental data. A new method for the determination of the starting time for the complex nucleation process was proposed. The formation rate of crystals under study decreases in the order:^*Fe(OH)₃>^*Fe(IO₃)₃>^*Fe₂S₃>^*Fe₂(C₂O₄)₃, in agar medium and^*Fe(OH)₃>^*Fe(IO₃)₃>^*FeC₂O₄)₃>^*FeS₃, in gelatine medium.     

Gas‐phase reactions of XH3+ (X = C,Si, Ge) with NF3: a comparative investigation on the detailed mechanistic aspects

The gas‐phase reaction of CH₃⁺ with NF₃ was investigated by ion trap mass spectrometry (ITMS). The observed products include NF₂⁺ and CH₂F⁺. Under the same experimental conditions, SiH₃⁺ reacts with NF₃ and forms up to six ionic products, namely (in order of decreasing efficiency) NF₂⁺, SiH₂F⁺, SiHF₂⁺, SiF⁺, SiHF⁺, and NHF⁺. The GeH₃⁺ cation is instead totally unreactive toward NF₃. The different reactivity of XH₃⁺ (X = C, Si, Ge) toward NF₃ has been rationalized by ab initio calculations performed at the MP2 and coupled cluster level of theory. In the reaction of both CH₃⁺ and SiH₃⁺, the kinetically relevant intermediate is the fluorine‐coordinated isomer H₃X‐F‐NF₂⁺ (X = C, Si). This species forms from the exoergic attack of XH₃⁺ to one of the F atoms of NF₃ and undergoes dissociation and isomerization processes which eventually result in the experimentally observed products. The nitrogen‐coordinated isomers H₃X‐NF₃⁺ (X = C, Si) were located as minimum‐energy structures but do not play an active role in the reaction mechanism. The inertness of GeH₃⁺ toward NF₃ is also explained by the endoergic character of the dissociation processes involving the H₃Ge‐F‐NF₂⁺ isomer. Copyright © 2009 John Wiley & Sons, Ltd.     

S,N,N′-Substituted sulfurdiimines as ligands: II. Compounds [(ν3-RC3H4)Pd{R1NS(R2)NR1}] (R  H,CH3;R1  aryl; R2  CH3, t-C4H9) and some related triazenido and amidino compounds of palladium(II)

The complexes [(ν³-RC₃H₄)Pd{R¹NS(R²)NR¹}] (R  H, CH₃;R¹  aryl; R²  CH₃, t-C₄H₉) have been obtained from the reaction of [(ν³-RC₃H₄)PdCl]₂ with [Li{R¹NS(R²)NR¹}]; two isomers are produced, differing in the orientation of the allyl group. The sulfurdiimino group has some π-allylic character. The compounds decompose in solution into azo—arenes and [(ν³-RC₃H₄)Pd(SR²)]₂, and this is shown to be dependent upon steric and electronic factors.The properties of the sulfurdiimino compounds are compared with those of the compounds [(ν³-RC₃H₄)Pd(R³N₃R³)]₂ and [(ν³-RC₃H₄)Pd(R³NC(R⁴)NR³)]₂ (R  H, CH₃;R³  CH₃, aryl; R⁴  H, CH₃), which have been prepared by new methods.     

Die Reaktion von Tellurhexafluorid mit Trimethylamin,Strukturen der TeF5−- und SeF5−-Anionen

Reaction of Telluriumhexafluoride and Trimethylamine, Structures of the TeF₅^? and SeF₅^? Anions The reaction of TeF₆ and (CH₃)₃N is of the redox kind, resulting in reduction of tellurium: X-ray single crystal analysis reveals the compounds (CH₃)₂N? CH₂? N(CH₃)₂⁺TeF₅^? and [(CH₃)₃NH⁺]₅(TeF₅^?)₃(HF₂^?)₂. By comparison with published data it can be shown that this mixture is identical to previously published [(CH₃)₃N]₂TeF₆. The latter was supposed to be one of the few examples of tellurium in a coordination state of eight. (CH₃)₄N⁺TeF₅^? and (CH₃)₄N⁴SeF₅^? are obtained and their structure is investigated by single crystal x-ray methods also. The anions SF₅^?, SeF₅^? and TeF₅^? are discussed in terms of weak interactions.     

Production of 1 Δg O2 from microwave discharges in CO2, NO2 and SO2

The production of ¹Δ_g O₂ in microwave discharges in CO₂ and NO₂ has been confirmed by the observation of its EPR spectrum. Quantitative measurements of the EPR spectra of ¹Δ_g and ³Σ⁺_g O₂ and ³P O atoms yield conversion efficiencies for these species. These combined measurements its show that the observed ¹Δ_g O₂ is not formed by simple excitation of ³Σ⁺_g O₂ formed in the discharge. Rather there must exist a direct mechanism for the production of ¹Δ_g O₂ from CO₂ and NO₂. The SO₂ discharge products give rise to no ¹Δ_g O₂ EPR spectrum.     

Equilibrium constants of HF,F-, HF-2 and H2F2 species in formic acid.

Equilibrium constants for the fluorinated species HF, F^-, HF^-₂ and H₂F₂ in formic acid and in a 1M potassium formate solution in formic acid have been studied by ¹⁹F NMR. The chemical shifts of these species have been determined from measurements of the shifts for various initial mixtures of differing concentrations of dissolved HF, F^- and HF^-₂. From these values, relative concentrations of HF, F^-, and HF^-₂ and H₂F₂ in each solution have been calculated through a numerical method. The following constants were obtained: K₁ = [H⁺][F^-]/[HF] = 1.1 x 10^-5M; K_D = [HF][F^-]/[HF^-₂] = 0.5 M; K′₁ = [H⁺][HF^-₂]/[H₂F₂]= 1.1 x 10^-5 M; K′_D = [HF]²/[H₂F₂]=0.5 M.     

Absorption,fluorescence and phosphorescence spectra of the singlet and triplet states of s-tetrazine in the crystal and in mixed crystals at low temperatures

The electronic absorption, fluorescence and phosphorescence spectra of s-tetrazine at low temperatures (4.2-1.5 K) are reported and analyzed in the neat crystal and in several mixed crystals. The ³B_3u-¹A_g (nπ^*) origin is at 18414 ± 5 cm^?1 for neat tetrazine. In the mixed crystal several sites identified. The lowest energy origin is at 17453 cm^?1 for tetrazine in pyrazine; 17 701 cm^?1 in pyrimidine; and 17 676 cm^?1 in pyridazine. The ^eB_3u-¹A_g (nπ^*) origin is at 14 096 ± 2 cm^?1 for the neat crystal. The phosphorescence lifetime of neat tetrazine is measured to be 96.8 ± 2.1 μs at 4.2 and 1.8 K. All the spectra are predominately composed of members of progressions in a single totally symmetric mode (ν_6a) built upon site origins and vibrational fundamentals. The ν_6a interval is: 743 (¹A_g), 715 (³B_3u), and 709 cm^?1 (¹B_3u) in the neat tetrazine crystal; 732 (¹A_g) and 705 cm^?1 (¹B_3u in pyrazine host, 737 (¹A_g) and 701 cm^?1 (¹B_3u) in pyrimidine host, and 732 (¹A_g) and 703 cm^?1 (¹B_3u) in pyridazine host mixed crystals. All emission spectra may be analyzed by Oi → (ν″_6a)^o_n (i), i indicating the observed s     

金属组学在急性心肌梗死早期诊断的应用

为探讨急性心肌梗死(AMI)患者血清中K⁺、Na⁺、Ca²⁺、Fe²⁺、Mg²⁺含量变化,并研究其与心肌梗死患者之间的关系。选取2022年5月至2023年2月收治的AMI患者37例,同时选取健康体检者35例作为对照组。依据入院时或体检时收集的抽血样本进行临床生化分析,比较两组间血清K⁺、Na⁺、Ca²⁺、Fe²⁺、Mg²⁺含量,采用判别方程、主成分分析法(PCA),判断分析哪种金属离子对于心肌梗死的诊断价值大。结果表明,AMI患者的血清中Ca²⁺和Fe²⁺含量低于健康对照组,差异具有统计学意义。基于血钙、铁水平两组具有显著性差异,以它们为基础进行判别分析,获得判别函数式。将血清中K⁺、Na⁺、Ca²⁺、Fe²⁺、Mg²⁺     

Photoinduced electron transfer of fullerenes (C60 and C70) studied by transient absorption measurements in near-IR region

Efficiencies and rates of electron transfer from various electron donors to excited fullerenes (C₆₀ and C₇₀) have been determined by observing the transient absorption bands in the near-IR region, where the anion radicals of fullerenes appear. From the rise of the absorption bands of C₆₀ ⁻⁺ and C₇₀ ⁻⁺ in the near-IR region, electron transfer takes place via the triplet states (^TC₆₀ ^* and ^TC₇₀ ^*) under appropriately low concentrations of electron donors. By analysis of the rise curves C₆₀ ⁻⁺ and C₇₀ ⁻⁺, contribution of the excited singlet states (^SC₆₀ ^* and ^SC₇₀ ^*) in addition to the route of the triplet states (^TC₆₀ ^* and ^TC₇₀ ^*) is confirmed. The quantum yield for electron transfer via the triplet states Φ_ct ^T was evaluated by the ratio of [C₆₀ ⁻⁺]/[^TC₆₀ ^*] (or [C₇₀ ⁻⁺/[^TC₇₀ ^*]). The Φ_ct ^T depends upon the donor-ability, donor concentration, and solvent polarity. The back electron-transfer process, which was evaluated by observing C₆₀ ⁻⁺, also depends upon the solvent polarity.     

Base Catalysed Racemization of Ethylenediamine-N,N,N′-triacetato-aqua-cobalt(III)

The kinetics of the base catalysed racemization of [Co(EN3A)H₂O]

1 Abbreviations: EN3A^3?=(^?OOCCH₂)₂N(CH₂)₂NHCH₂COO^?; ME3A^3?=(^?OOCCH₂)₂N(CH₂)₂ N(CH₃)CH₂COO^?; EDDA^2?=^?OOCCH₂NH(CH₂)₂NHCH₂COO^?; EDTA^4?=(^?OOCCH₂)₂N(CH₂)₂N(CH₂COO^?)₂;TNTA^4?=(^?OOCCH₂)₂N(CH₂)₃N(CH₃COO^?)₂; HETA^3?=(^?OOCCH₂)₂N(CH₂)₂N(CH₂COO^?)CH₂CH₂OH; en=H₂N(CH₂)₂NH₂; Meen=H₂N(CH₂)₂NHCH₃; sar^?=^?OOCCH₂NHCH₃.

were studied polarimetrically in aqueous buffer solution. The reaction rate is first order in OH^? and in complex, in weakly acidic medium. Activation parameters are ΔH≠=22 kcal · mol^?1, ΔS≠=26 cal · K^?1. The results are discussed in terms of an S_N1CB mechanism involving exchange of the ligand water molecule. The N-methylated analogue [Co(ME3A)H₂O] does not racemize in the pH-range investigated. Loss of optical activity occurs at a rate which is about 1,000 times slower than the racemization of [Co(EN3A)H₂O](60°) and coincides with the decomposition of the complex.     

Conductivity and Redox Potentials of Ionic Liquid Trihalogen Monoanions [X3]−, [XY2]−, and [BrF4]− (X=Cl,Br, I and Y=Cl,Br)

The ionic liquid (IL) trihalogen monoanions [N₂₂₂₁][X₃]⁻ and [N₂₂₂₁][XY₂]⁻ ([N₂₂₂₁]⁺=triethylmethylammonium, X=Cl, Br, I, Y=Cl, Br) were investigated electrochemically via temperature dependent conductance and cyclic voltammetry (CV) measurements. The polyhalogen monoanions were measured both as neat salts and as double salts in 1-butyl-1-methyl-pyrrolidinium trifluoromethane-sulfonate ([BMP][OTf], [X₃]⁻/[XY₂]⁻ 0.5 M). Lighter IL trihalogen monoanions displayed higher conductivities than their heavier homologues, with [Cl₃]⁻ being 1.1 and 3.7 times greater than [Br₃]⁻ and [I₃]⁻, respectively. The addition of [BMP][OTf] reduced the conductivity significantly. Within the group of polyhalogen monoanions, the oxidation potential develops in the series [Cl₃]⁻>[BrCl₂]⁻>[Br₃]⁻>[IBr₂]⁻>[ICl₂]⁻>[I₃]⁻. The redox potential of the interhalogen monoanions was found to be primarily determined by the central halogen, I in [ICl₂]⁻ and [IBr₂]⁻_, and Br in [BrCl₂]⁻. Additionally, tetrafluorobromate(III) ([N₂₂₂₁]⁺[BrF₄]⁻) was analyzed via CV in MeCN at 0 °C, yielding a single reversible redox process ([BrF₂]⁻/[BrF₄]⁻).     

Oxidation of Ascorbate by Ni(III) Complexes with Tetraaza-macrocyclic Ligands in Neutral Aqueous Solutions. A Pulse-Radiolysis Study

Abstract

The mechanisms and kinetics of oxidation of ascorbate, AH^?, by Ni(III)Lⁱ _aq and by LⁱNi(III) (HPO₄)₂ ^? complexes (L¹ = meso-(5,12)-7,7,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane; L² = 1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane) in neutral aqueous solutions have been investigated.

The oxidation of ascorbate by the LⁱNi(III) (HPO₄)₂ ^? and Ni(III)L¹ _aq proceeds via two consecutive reactions well separated in time. The products of the first reaction are the A^.? radical anion and the corresponding Ni(II) complex. The oxidations by the LⁱNi(III)(HPO₄)₂ ^? complexes proceed via the outer sphere mechanism, whereas the detailed mechanism of reaction of Ni(III)L¹ _aq cannot be determined. The rate of reaction decreases with the increase in the concentration of phosphate, thus indicating that LⁱNi(III)(HPO₄)(H₂O)⁺ and LⁱNi(III)OH²⁺ are stronger oxidizing agents than LⁱNi(III)(HPO₄)^? ₂.

The oxidation of ascorbate by Ni(III)L² _aq proceeds via three consecutive reactions which are well separated in time. Thus the results clearly point out that this process occurs via the inner sphere mechanism. The first transient observed is tentatively identified as L²(H₂O)Ni(II)(A^.?)²⁺, i.e., an unexpected complex of the ascorbate anion radical. Also in this process the last transient observed is the A^.? anion radical. The stabilization of the ascorbyl radical in a transient complex might be of biological significance.     

A 1,3‐Capped Calix[4] Conjugate Possessing an Amine Moiety as an Anion Receptor: Reversible Anion Sensing Detected by Spectroscopy and Characterization of the Supramolecular Features by Microscopy

A phenylenediamine‐capped conjugate of calix[4]arene ( L_amino ) was synthesized by reducing its precursor, L_imino , with sodium borohydride in methanol. The L_amino sample binds to anions due to the more flexible and bent conformation of the capped aminophenolic binding core, compared to the precursor L_imino . The L_amino sample showed selectivity towards H₂PO₄^? by exhibiting a ratiometric increase in emission by about 11‐fold with a detection limit of (1.2±0.2) μm ((116±20) ppb) over 15 anions studied, including other phosphates, such as P₂O₇^4?, adenosine monophosphate (AMP^2?), adenosine diphosphate (ADP^2?), and adenosine triphosphate (ATP^2?). The L_amino sample shows an increase in the absorbance at λ=315 nm in the presence of H₂PO₄^?, CO₃^2?, HCO₃^?, CH₃CO₂^?, and F^?. The ¹H NMR spectroscopic titration of L_amino with H₂PO₄^?, F^?, and CH₃CO₂^? showed major changes in the phenylene‐capped and salicyl moieties, and thereby, confirming the aminophenolic region as the binding core. However, the binding strength of these anions followed the trend H₂PO₄^?>F^??CH₃CO₂^?>HSO₄^?. The heat changes observed by isothermal titration calorimetry support this trend. The L_amino sample showed reversible sensing towards H₂PO₄^? and F^? in the presence of Mg²⁺ and Ca²⁺, respectively. NOESY studies of L_amino , in comparison with its anionic complexes, revealed that major conformational changes occurred in the capping region to facilitate the binding of anion. ESI‐MS and the Job's method revealed 1:1 stoichiometry between L_amino and H₂PO₄^? or F^?. In the SEM micrographs of L_amino , the spherical particles are converted into spherical aggregates and further form large agglomerates and even branched sheets in the presence of anions, depending upon their binding strength.     

Permeability of polymer materials to compounds containing radionuclides

The permeability of rubber and PE gloves, PE bags and strippable PVC paint to HTO, Na¹²⁵I, H₂ ³⁵SO₄, H₃ ³²PO₄,¹⁴¹CeCl₃,⁸⁹SrCl₂, and,¹³⁷CsCl in aqueous solution was tested. All materials were permeable to HTO and Na¹²⁵I. Whereas rubber gloves were permeable the other materials were impermeable to H₂ ³⁵SO₄. The remaining radioactive compounds showed no penetration. The diffusion coefficients of the penetrating compounds were calculated on the basis of Fick's First Law for the respective materials. The permeability to Na¹²⁵I and HTO decreases in the order rubber, PVC paint, and PE. Penetration increases in the order H₂ ³⁵SO₄, Na¹²⁵I, and HTO.     

Ion‐Pairing of Phosphonium Salts in Solution: C?H⋅⋅⋅Halogen and C?H⋅⋅⋅π Hydrogen Bonds

The ¹H NMR chemical shifts of the C(α)? H protons of arylmethyl triphenylphosphonium ions in CD₂Cl₂ solution strongly depend on the counteranions X^?. The values for the benzhydryl derivatives Ph₂CH? PPh₃⁺ X^?, for example, range from δ_H=8.25 (X^?=Cl^?) over 6.23 (X^?=BF₄^?) to 5.72 ppm (X^?=BPh₄^?). Similar, albeit weaker, counterion‐induced shifts are observed for the ortho‐protons of all aryl groups. Concentration‐dependent NMR studies show that the large shifts result from the deshielding of the protons by the anions, which decreases in the order Cl^? > Br^? ? BF₄^? > SbF₆^?. For the less bulky derivatives PhCH₂? PPh₃⁺ X^?, we also find C? H???Ph interactions between C(α)? H and a phenyl group of the BPh₄^? anion, which result in upfield NMR chemical shifts of the C(α)? H protons. These interactions could also be observed in crystals of (p‐CF₃‐C₆H₄)CH₂? PPh₃⁺ BPh₄^?. However, the dominant effects causing the counterion‐induced shifts in the NMR spectra are the C? H???X^? hydrogen bonds between the phosphonium ion and anions, in particular Cl^? or Br^?. This observation contradicts earlier interpretations which assigned these shifts predominantly to the ring current of the BPh₄^? anions. The concentration dependence of the ¹H NMR chemical shifts allowed us to determine the dissociation constants of the phosphonium salts in CD₂Cl₂ solution. The cation–anion interactions increase with the acidity of the C(α)? H protons and the basicity of the anion. The existence of C? H???X^? hydrogen bonds between the cations and anions is confirmed by quantum chemical calculations of the ion pair structures, as well as by X‐ray analyses of the crystals. The IR spectra of the Cl^? and Br^? salts in CD₂Cl₂ solution show strong red‐shifts of the C? H stretch bands. The C? H stretch bands of the tetrafluoroborate salt PhCH₂? PPh₃⁺ BF₄^? in CD₂Cl₂, however, show a blue‐shift compared to the corresponding BPh₄^? salt.