Triiodide‐Mediated δ‐Amination of Secondary C−H Bonds

The C_δ?H amination of unactivated, secondary C?H bonds to form a broad range of functionalized pyrrolidines has been developed by a triiodide (I₃^?)‐mediated strategy. By in situ 1) oxidation of sodium iodide and 2) sequestration of the transiently generated iodine (I₂) as I₃^?, this approach precludes undesired I₂‐mediated decomposition which can otherwise limit synthetic utility to only weak C(sp³)?H bonds. The mechanism of this triiodide‐mediated cyclization of unbiased, secondary C(sp³)?H bonds, by either thermal or photolytic initiation, is supported by NMR and UV/Vis data, as well as intercepted intermediates.     

Ternary diffusion with charged-complex formation in aqueous I2+NaI and I2+KI solutions

Diaphragm cells have been used to measure ternary diffusion coefficients for I₂+NaI and I₂+KI in aqueous solution at 25°C. Although most of the iodine molecules are bound to iodide ions and are transported as the triiodide species [I₂(aq)+I^–(aq)=I ₃ ^– (aq)], diffusion of the iodide salts produces relatively small countercurrent coupled flows of the iodine component. The ternary diffusivity of the iodine component in the solutions is 10 to 20% larger than the diffusivity of the triiodide species. This behavior can be understood by considering electrostatic coupling of the ionic flows. The diffusion equations for I₂+NaI and I₂+KI components are reformulated in terns of NaI₃+NaI and KI₃+KI mixed electrolyte components.     

Zur Struktur zweier Isothiazolium‐Polyiodide (C19H16FeNS)I5 und (C15H12NS)2I8

On the Structure of Two Isothiazolium Polyiodides (C₁₉H₁₆FeNS)I₅ and (C₁₅H₁₂NS)₂I₈ By oxidation of 3‐phenylamino thiopropenones with iodine two isothiazolium polyiodides were obtained, whose structures have been determined by X‐ray structure analysis. 2‐Phenyl‐5‐ferrocenyl‐isothiazolium pentaiodide(C₁₉H₁₆FeNS)I₅ forms a layer structure with isothiazolium cations and polyiodide anions. The polyiodide layers contain pentaiodide ions I₅^–, triiodide ions I₃^– and iodine molecules I₂. Bis(2,5‐diphenyl‐isothiazolium) octaiodide (C₁₅H₁₂NS)₂I₈ also forms a layer structure with isothiazolium cations and polyiodide anions. The polyiodide layers are built up by octaiodide ions I₈^2–, pentaiodide ions I₅^– and triiodide ions I₃^–.     

Spectrophotometric analysis of iodide oxidation by chlorine in highly mineralized solutions

A spectrophotometric method for determining the concentrations of various iodine compounds (I⁻: initial compound, I₃⁻: under-oxidized iodine form, I₂ and I₂Cl⁻: target iodine forms and ICl₂⁻: over-oxidized iodine form) in their joint presence has been developed in order to study iodine processing from underground brines in Turkmenistan which are characterized by considerably higher mineralization and lower iodide content compared than those in Japan and USA. It was found that solutions with constant iodine concentrations and variable chloride concentrations had an isosbestic point at 474 nm with a molar absorbtivity of I₂ plus I₂Cl⁻ of 610.2 l mol⁻¹ cm⁻¹, while the absorbance of other iodine forms at this wavelength was negligible. This allowed us to use an absorbance at 474 nm for calculating the iodine concentration in solutions of variable chloride concentration. For calculating concentrations of other iodine compounds, absorbances at other wavelengths were used: 225 nm (I⁻ and ICl₂⁻), 248 nm (I₂Cl⁻) and 350 nm (I₃⁻). Beer’s law was valid for all iodine compounds in solutions with constant salt concentrations at all wavelengths. The authors have also developed a detailed algorithm for calculating the concentrations of the various iodine forms in their joint presence. The method was applied to solutions with various chloride concentrations and additions of microcomponents of natural solutions (bromide and iron ions, naphthenic acid and hydrogen sulfide). The overall precision for calculating the concentrations of various iodine compounds was <5% for solutions with an oxidant excess of <2-fold, and with chloride concentrations of <5 mol l⁻¹.     

Complex structure tri- and polyiodides of iodocyclization products of 2-allylthioquinoline

Iodocyclization products of 2-allylthioquinoline are obtained in the form of polyiodides with different stoichiometric compositions. X-ray crystallography data are analyzed for two different crystal structures of 1-iodomethyl-1,2-dihydro[1,3]thiazolo[3,2-a]quinolinium polyiodides: triiodide C₁₂H₁₁INS⁺I ₃ ^? and complex polyiodide 2(C₁₂H₁₁INS⁺I ₃ ^? )·I₂. A comparison is made of the nonbonding interactions of dihydrothiazoloquinolinium with atoms of the triiodide anion and complex polyiodide to show the crystal structure features attributed to the participation of molecular iodine.     

Electronic structures and reactivities of iodinating agents in the gas phase and in solutions: A density functional study

The electronic and spatial structures of a broad spectrum of neutral compounds with X-Hal (X = N, O, Cl; Hal = Cl, Br, I) bonds and their protonated forms and of different electronic states of triiodide cation, I₃ ⁺, were determined from density functional B3LYP/6 311G* quantum chemical calculations. The effects of the structure of these compounds on the parameters of electrophilic reactivity were revealed and the thermochemical characteristics of homolytic and heterolytic X-Hal bond dissociation and of iodine transfer in hydroxyl-containing solvents were calculated. Due to low homolytic bond dissociation energies of X-I, the formation of molecular iodine and triiodide cation I₃ ⁺ becomes thermodynamically favorable and the cation should act as iodinating agent alternative to acylhypoiodites and N-iodoimides. The solvation effects of MeOH and CH₂Cl₂ on the X-Hal bond homolysis and heterolysis were determined using the PCM model. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1280–1288, August, 2006.     

Reaction of polyamine polymer with molecular iodine via charge-transfer complex formation

The reaction of a Mannich base type-polyamine polymer with iodine (I₂) was studied kinetically and thermodynamically in order to clarify the polymer effects in the formation of triiodide ions (I₃^?). N,N-Dimethyl-p-(4-methylpiperazinomethyl) aniline and 1,4-dimethylpiperazine were used as low molecular weight donor model compounds. Triiodide ions are produced from the polyamine–I₂ system immediately after mixing the two-component solutions, while in the systems with I₂ and N,N-dimethyl-p-(4-methyl-piperazinomethyl)aniline and 1,4-dimethylpiperazine they are obtained only when relatively high concentrations of both donor and acceptor solutions were mixed. This is explained by the entropic contributions of the polymer chain such as the stacking effect of donor nitrogen atoms, i.e., the increment of local donor concentration around I₂ in the reaction field. The relation between the solution behavior of the reaction systems and the rate of formation of I₃^? ions also supports this kind of polymer effect. The effects of neighboring groups and dielectric constant on the reaction are also discussed.     

Untersuchungen an Polyhalogeniden. XVI. Darstellung und Kristallstrukturen der Bipyridiniumpolyiodide Bipy · HIn mit n = 3, 5 und 7

Studies on Polyhalides. 16. Preparation and Crystal Structures of Bipyridiniumpolyiodides Bipy · HI_n with n = 3, 5, and 7 With simply protonated α,α′-Bipyridyl Bipy · H⁺ a triiodide Bipy · HI₃, a pentaiodide Bipy · HI₅ and a heptaiodide Bipy · HI₇ may be prepared in the presence of iodide ions I^? and dependent of the iodine I₂ content. Bipyridiniumtriiodide C₁₀H₉N₂I₃ crystallizes at room temperature monoclinically in P2₁/n with a = 1 122.8(1) pm, b = 1 072.7(1) pm, c = 1 200.2(3) pm, β = 98.02(2)° and Z = 4. The crystal structure is built up from mixed cationic and anionic layers. Bipyridiniumpentaiodide C₁₀H₉N₂I₅ crystallizes at room temperature monoclinically in P2₁/c with a = 887.3(5) pm, b = 2 527.9(12) pm, c = 830.7(3) pm, β = 106.78(5)° and Z = 4. The crystal structure contains triiodide ions I₃^? till now uniquely connected by iodine molecules I₂ in a trigonal planar way. Bipyridiniumheptaiodide C₁₀H₉N₂I₇ crystallizes at room temperature triclinically in P&1macr; with a = 713.1(3) pm, b = 1 007.9(3) pm, c = 1 464,8(4) pm, α = 81.07(3)°, β = 89.92(3)°, γ = 82.77(3)° and Z = 2. The crystal structure contains a V-shaped pentaiodide ion I₅^? completed by an iodine molecule I₂ to a trigonal pyramidally shaped heptaiodide ion I₇^? and at the same time connected to a zigzag chain.     

Crystal and molecular structure of diphenyliodonium triiodide

A new salt diphenyliodonium triiodide (C₁₂H₁₀I₄) was obtained. The [C₁₂H₁₀I⁺][I₃⁻] compound was isolated as red brown crystals and studied by single-crystal X-ray diffraction. The structure of diphenyliodonium triiodide consists of separate, virtually linear I₃⁻ anions and C₁₂H₁₀I⁺ cations. Strong intermolecular anion-anion (I₃⁻…I₃⁻) and anion-cation (I₃⁻…I⁺) interactions in the crystal structure leads to a change in the symmetry of triiodide ions. The complex formation in the system organic cation iodide-elementary iodine was studied by spectrophotometry. The complex composition was found (1: 1), and the stability constant of the complex in chloroform was determined (loggB = 3.91).     

An All Solid State Potentiometric Sensor for Monohydrogen Phosphate Ions

An all solid state potentiometric sensor using anthracene thiourea derivative as ionophore was developed. It exhibited a near‐Nernstian slope of 30.8±1.0 mV/decade of activity for HPO₄^2? ions in the concentration range of 1.0×10^?7–1.0×10^?3 M at pH 7.4. It displayed excellent selectivity for monohydrogen phosphate over other anions and the selectivity sequence was determined as HPO₄^2?>SO₄^2?>Cl^?>NO₃^?>OAc^?>I^?>ClO₄^?. The developed sensor was evaluated for the analysis of monohydrogen phosphate ions in a standard reference material (SRM 1548) as well as in the potentiometric titration of phosphate ions with a barium chloride solution.     

Adsorption of Cl<Superscript>−</Superscript> ions on γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> oxide from nitrate solutions

The adsorption of chloride ions on γ-Fe₂O₃ oxide (maggemite) from nitrate solution is studied using the method of potentiometric titration and an ion-selective electrode. The specific character of adsorption is determined. It is shown that the maggemite surface coverage with Cl^? ions increases with increasing concentration of ions in the solution, decreasing pH value, and increasing potential. The adsorbability of ions changes drastically in the pH range about pH₀ (γ-Fe₂O₃)6.2. It is found that the adsorption of chloride ions from neutral nitrate solution exponentially increases in the potential range from 0.1 to 1.0 V. The type of adsorption isotherm and the adsorption parameters are determined. It is found that, in the absence of external polarization, the concentration dependences of adsorption of Cl^? ions are complex-shaped, and their initial portions are described by the Langmuir isotherm. Further increase of adsorption is explained by the penetration of Cl^? ions inwards the oxide.     

Building up 1‐D, 2‐D,and 3‐D Polyiodide Frameworks by Finely Tuning the Size of Aryls on Ar‐S‐TTF in the Charge‐Transfer (CT) Complexes of Ar‐S‐TTFs and Iodine

The arylthio‐substituted tetrathiafulvalenes (Ar‐S‐TTFs) are electron donors having three reversible states, neutral, cation radical, and dication. The charge‐transfer (CT) between Ar‐S‐TTFs ( TTF1 — TTF3 ) and iodine (I₂) is reported herein. TTF1 — TTF3 show the CT with I₂ in the CH₂Cl₂ solution, but they are not completely converted into cation radical state. In CT complexes of TTF1 — TTF3 with I₂, the charged states of Ar‐S‐TTFs are distinct from those in solution. TTF1 is at cation radical state, and TTF2 — TTF3 are oxidized to dication. The iodine components in complexes show various structures including 1‐D chain of V‐shaped (I₅)^–, and 2‐D and 3‐D iodine networks composed of I₂ and (I₃)^–.     

Electrochemiluminescence Quenching by Halide Ions at Bipolar Electrodes

Quenching of Ru(bpy)₃²⁺ electrochemiluminescence (ECL) by Cl^?, Br^?, and I^? ions was studied as a function of halide concentration in a bipolar electrochemical cell. All of the halides investigated showed similar qualitative behavior: above a critical concentration, ECL intensity was found to decrease linearly as the halide ion concentration was increased, due to dynamic quenching of Ru(bpy)₃²⁺ ECL. Stern‐Volmer slopes (K_SV) of 0.111±0.003, 4.2±0.3, and 6.2±0.3 mM^?1 were measured for Cl^?, Br^? and I^?, respectively. The magnitude of K_SV correlates with halide ion oxidation potential, consistent with an electron transfer quenching mechanism. Using the bipolar platform described herein, aqueous, halide‐containing solutions could be quantified rapidly using the sequential standard addition method. The lower detection limit is determined by a complex mechanism involving the competitive electrooxidation of halide ions and the ECL co‐reactants, as well as the passivation of the surface of the bipolar electrode, and was found to be 0.20±0.01, 0.08±0.01 and 10±1 mM, respectively, for I^?, Br^?, and Cl^?. The performance of the bipolar ECL quenching assay is comparable to previously published fluorescence quenching methods for the determination of halide ions, while being much simpler and less expensive to implement.     

Untersuchungen an Polyhalogeniden. XXVII. Über Tetra(n-propyl)ammoniumpolyiodide (n-Pr4N)In mit n = 3, 5, 7: Darstellung und strukturelle Charakterisierung eines Triiodids (n-Pr4N)I3, eines Pentaiodids (n-Pr4N)I5 und eines Heptaiodids (n-Pr4N)I7

Studies of Polyhalides. 27. On Tetra(n-propyl)ammonium Polyiodides (n-Pr₄N)I_n with n = 3, 5, 7: Preparation and Crystal Structures of a Triiodide (n-Pr₄N)I₃, a Pentaiodide (n-Pr₄N)I₅, and a Heptaiodide (n-Pr₄N)I₇ [(n-C₃H₇)₄N]I₃, [(n-C₃H₇)₄N]I₅ and [(n-C₃H₇)₄N]I₇ have been prepared by the reaction of tetra(n-propyl)ammoniumiodide [(n-C₃H₇)₄N]I with iodine I₂ in ethanol. Their crystal structures have been determined by single crystal X-ray diffraction methods. The triiodide is built up from layers of the quarternary ammonium ions n-Pr₄N⁺ and from two independent differently packed centrosymmetric triiodide ions I₃^? which alternate with each other along [100]. The pentaiodide ion forms slightly puckered almost squared nets perpendicular [001] of iodide ions which are connected with four iodine molecules by secondary bonds. The meshes from twelve iodine atoms include the cations. The centrosymmetric Z-shaped heptaiodide ion is built up from a linear symmetric triiodide ion and two iodine molecules forming twisted rope ladders along [001] which are separated by stacks of cations.     

Bis(2‐chloro‐N‐methyl­pyridinium) iodide triiodide

The title compound, 2C₆H₇ClN⁺·I^?·I₃^?, crystallizes with undulating layers of chains containing alternate iodide and triiodide anions formed from iodine and the heterocyclic iodide salt.     

Synthesis and structural characterization of cadmium(II) complexes of tetramethylthiourea (Tmtu); X-ray structure of [Cd(Tmtu)2Cl2]

The spectral characterization of cadmium(II) complexes of the general formula [Cd(Tmtu)₂X₂] (Tmtu = tetramethylthiourea, X = Cl^?, Br^?, I^?, and SCN^?) as well as the X-ray structure of one of them, [Cd(Tmtu)₂Cl₂] (I) is described. In (I), the cadmium atom lies on a twofold rotation axis and has a distorted tetrahedral coordination environment defined by two S atoms of telramelhylthioures (Tmtu) ligands and two chloride ions. The crystal structure is stabilized by non-classical intramolecular C-H?N and C-H?S hydrogen bonding interactions involving the methyl H and sulfur or nitrogen atoms. The spectroscopic data were discussed in terms of the nature of bonding.     

Ferric Chloride Complexes in Aqueous Solution: An EXAFS Study

A series of concentrated aqueous solutions of ferric chloride with different chloride:iron(III) ratios has been studied by means of EXAFS to determine the structure around the iron(III) ion of the dominating species in such solutions. The dominating species in dilute acidic aqueous solution of ferric chloride, at less than 1 mmol·dm^?3, are the hydrated iron(III) and chloride ions, while in concentrated aqueous solution and in solutions with an excess of chloride ions, up to 1.0 mol·dm^?3, it is the trans-[FeCl₂(H₂O)₄]⁺ complex. Possible higher chloroferrate(III) or dimeric [Fe₂Cl₆] complexes at room temperature, as proposed in the literature, were not observed in any of the studied solutions in spite of an excess of chloride ions of 1 mol·dm^?3.     

Isolierte I102−‐Ringe,ein neues Strukturelement in der Polyiodid‐Chemie

The novel compound bis(1,4,7,10‐tetraoxa­cyclo­do­decane)­cadmium(II) decaiodide, [Cd(C₈H₁₆O₄)₂]I₁₀, contains the [Cd(12‐crown‐4)₂]²⁺ complex cation, triiodide ions and iodine mol­ecules. Two triiodide ions and two iodine mol­ecules form isolated twisted I₁₀^2? rings. The geometry of the complex cation is as expected, e.g.d(Cd—O) = 2.366 (4) and 2.394 (4) Å.     

Structure of iodide ion arrays in iodinated nylon 6 and the chain orientation induced by iodine in nylon 6 films

Two species of iodide ions (I₃^? and I₅^?) are found in iodine—nylon 6 complexes. Orientation of I₅^? arrays (most likely I₂/I₃^? complex) along the polymer chain and I₃^? ions perpendicular to the chain axis in uniaxially drawn films and in films with planar orientation suggests that there is and intrinsic relation between the direction of iodide ion arrays and nylon 6 chains. When an unoriented film of nylon 6 in the amorphous or the α crystalline form is treated with an aqueous solution of iodine—potassium iodide, the I₃^? species in the resulting iodine—nylon complex lie in planes parallel to the surface of the film, and I₂/I₃^? units are oriented normal to the surface of the film. The γ form obtained by desorbing the iodine from this complex shows considerable uniaxial rientation with the nylon chains oriented perpendicular to the plane of the film; this orientation is maintained during the γ to α transition. It is proposed that the iodine-induced orientation of the nylon 6 chains is due to the nucleating effects of the iodide ion species as the iodine diffuses unidirectionally into the film.     

Photoelectron spectra of quaternary salts in solution

The ionisation energies, measured by He(I) photoelectron spectroscopy, are reported for I^?, Cl^?, Br^?, CNS^? and NO^?₂ in adiponitrile solution. These energies give a straight line when plotted against the energies of the electron transfer to solvent absorption bands of the ions in acetonitrile solution. The intercept gives the electron affinity of the solvent; for acetonitrile, assumed to be spectroscopically equivalent to adiponitrile, the electron affinity is found to be 1.85 eV; for water it is 1.65 eV. The energies of electron transfers not observable in the UV absorption spectrum of NO^?₂ solutions are estimated from the photoelectron spectra.