Kinetics of the solvolysis oftrans-dichlorotetra-(4-t-butylpyridine)-cobalt(III) ions in water +t-butyl alcohol mixtures

Rates of solvolysis of the complex cation [Co(4tBupy)₄Cl₂]⁺ have been determined in mixtures of water with the hydrophobic solvent, t-butyl alcohol. The solvent composition at which the extremum is found in the variation of the enthalpy H^* and the entropy S^* of activation correlates well with the extremum in the variation of the relative partial molar volume of t-butyl alcohol in the mixture and the straight line found for the variation of H^* with S^* is coincident with the same plot for water + 2-propanol mixtures. A free energy cycle is applied to the process initial state (C ⁿ⁺) going to the transition state [M⁽ⁿ⁺¹⁾⁺...Cl^–] in water and in the mixture using free energies of transfer of the individual ionic species, G _t ^o (i), from water into the mixture. Values for G _t ^o (i) are derived from the solvent sorting method and from the TATB/TPTB method: using data from either method, changes in solvent structure on going from water into the mixture are found to stabilize the cation in the transition state, M⁽ⁿ⁺¹⁾⁺, more than in the initial state, C ⁿ⁺. This is compared with the application of the free energy cycle to the solvolysis of complexes [Co(Rpy)₄Cl₂]⁺ and [Coen₂LCl]⁺ in mixtures of water with methanol, 2-propanol or t-butyl alcohol: the above conclusion regarding the relative stabilization of the cations holds for all these complexes in their solvolyses in water+alcohol mixtures using values of G _t ^o (Cl^–) from either source.     

Kinetics of the solvolysis of [Co(3Rpy)4Cl2]+ ions (R = Me or Et) in water and in water + methanol mixtures

Rates of solvolysis of ions [Co(3Rpy)₄Cl₂]⁺ with R = Me and Et have been measured over a range of temperatures for a series of water-rich water + methanol mixtures to investigate the effect of changes in solvent structure on the solvolysis of complexes presenting a largely hydrophobic surface to the solvent. The variation of the enthalpies and entropies of activation with solvent composition has been determined. A free energy cycle relating the free energy of activation in water to that in water + methanol is applied using free energies of transfer of individual ionic species from water into water + methanol. Data for the free energy of transfer of chloride ions ΔG(Cl^?) from both the spectrophotometric solvent sorting method and the TATB method for separating ΔG(salt) into ΔG(i) for individual ions are used: irrespective of the source of ΔG(Cl^?), in general, ?ΔG(Co(Rpy)₄Cl²⁺) > ?ΔG(Co(Rpy)₄Cl₂⁺), where Rpy = py, 4Mepy, 4Etpy, 3Etpy, and 3Mepy, showing that changes in solvent structure in water-rich water + methanol mixtures generally stabilize the cation in the transition state more than the cation in the initial state for this type of complex ion. A similar result is found when the free energy cycle is applied to the solvolysis of the dichloro (2,2′,2″-triaminotriethylamine)cobalt(III) ion. The introduction of a Me or Et group on the pyridine ring in [Co(Rpy)₄Cl₂]⁺ has little influence on the difference {ΔG(Co(Rpy)₄Cl²⁺)?ΔG(Co(Rpy)₄Cl₂⁺)} in water + methanol with the mol fraction of methanol < 0.20.     

The influence of solvent structure on the solvolysis oftrans-dichlorotetra (4-ethylpyridine) cobalt(III) perchlorate

Summary The solvolysis oftrans-[Co(4-Etpy)₄Cl₂]ClO₄, was followed spectrophotometrically in water/isopropanol at different temperatures. The activation energy varied nonlinearly with the mole fraction of the co-solvent, ₂. The plot of logk versus D _s ^–1 was also non-linear. These features were attributed to the differential solvation of the initial and transition states. On plotting H versus S, the points fall very close to straight line. The isokinetic temperature was found to be 334K, indicating that the solvolysis reaction is controlled by S and not H. The change in H and S with the mole fraction of the cosolvent shows extrema at the composition range where changes in solvent structure occur. The influence of the solvent structure on the complex ion in the transition state dominates over that in the initial state, where –G _t ⁰ [Co(4-Etpy)₄Cl]²⁺>–G _t ⁰ [Co(4-Etpy)₄Cl₂]⁺.     

The solvolysis oftrans-[Co(4-Mepy)4Cl2]ClO4 in water-methanol mixtures

Summary The solvolysis of thetrans-[Co(4-Mepy)₄Cl₂]ClO₄ complex was studied in 0 to 70% v/v H₂O: MeOH mixtures at 40, 45, 50 and 55 °C. The high negative S^* values found for the complex cation under investigation, relative to that oftrans- [Co(py)₄Cl₂]⁺ reported in the literature, were attributed to the substituent methyl groups. The free energies of transfer of both the ground and the transition states were calculated from which the dominant effect of the solvent on the transition state is apparent.     

Solubilities in aqueous mixtures oft-butanol andtrans-dichlorotetra(3-alkylpyridine) cobalt(III) hexachlororhenate(IV): Gibbs energies of transfer of the complex cations

The solubilities of the hexachlororhenate(IV) salts of the complex cations trans-[Co(3Mepy)₄Cl₂]⁺ and trans-[Co(3Etpy)₄Cl₂]⁺ have been determined in water+t-butyl alcohol mixtures. By reference to the solubilities of Cs₂ReCl₆ and the Gibbs energies of transfer of Cs⁺ from water into water+t-butyl alcohol mixtures, G _t ^o (Cs⁺), G _t ^o [Co(3Mepy)₄Cl ₂ ⁺ ] and G _t ^o [Co(3Etpy)₄Cl ₂ ⁺ ] are calculated. These latter values, when introduced into the equation for a free energy cycle applied to the process of the initial state going to the transition state for the solvolyses of these two cations, produces values for G _t ^o [Co(3Mepy)₄Cl^2+*] and G _t ^o [Co(3Etpy)₄Cl^2+*] for the Co³⁺ cations in the transition state. These values are compared with (G _t ^o (i) for i=[Co(Rpy)₄Cl₂]⁺, [Co(Rpy)₄Cl]^2+*, [Coen₂XCl]⁺ and [Coen₂X]^2+* to investigate the influence of the hydrophobicity of the surface of the complex on its stability in the mixtures. G _t ^o (i) (solvent sorting) are compared with G _t ^o (i) (TATB).     

Dimethylglyoximkomplexe des Kobalts(III) mit aromatischen Diaminen Über α-Dioximkomplexe der Übergangsmetalle, 37. Mitt.

Zusammenfassung Durch Oxydation von Kobalt(II)salz-Lösungen in Anwesenheit von Dimethylglyoxim und aromatischen Diaminen wurden unter doppelter Umsetzung 41 Salze der [Co(HD)₂(o-Phenylendiamin)₂]⁺, [Co(HD)₂(m-Phenylendiamin₂])⁺, [Co(HD)₂-(2-Methyl-p-phenylendiamin)₂]⁺ und [Co(HD)₂(N-Dimethyl-p-phenylendiamin)₂]⁺-Kationen erhalten. Die Koordination von zwei Diaminliganden im Kobalt(III)-bis-dimethylglyoximin-Kern bestätigt dietrans-Konfiguration der [Co(HD)₂(Diamin)₂]⁺-Komplexe. Diese Annahme wurde auch durch UR-spektroskopische Untersuchung bestätigt.

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On-dioxime complexes of transition metals, XXXVII. Cobalt(III)-dimethylglyoxime complexes with aromatic diamines

The oxidation of cobalt(II) salts in presence of dimethyl-glyoxime and aromatic diamines, has been studied. A series of 41 novel complex salts of the cations [Co(HD)₂(o-phenylendiamine)₂]⁺, [Co(HD)₂(m-phenylendiamine)₂]⁺, [Co(HD)₂(2-methyl-p-phenylendiamine)₂]⁺ and [Co(HD)₂(N-dimethyl-p-phenylendiamine)₂]⁺ has been prepared and characterized by means of double decomposition reactions.The coordination of 2 diamine molecules to the Co(III)-dimethylglyoximine-skelet confirms thetrans-configuration of the [Co(HD)₂(diamine)₂ ⁺ complexes.

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Mit 2 Abbildungen     

Solubility of dichlorotetraalkylpyridinecobalt III hexachlororhenate(IV) in water + methanol mixtures: Free energies of transfer of the complex cation from water into the mixtures

The solubility of salts [Co(3Rpy)₄Cl₂]₂]ReCl₆] has been determined in water + methanol mixtures. By comparing these with the solubilities of the salt Cs₂ReCl₆ and using calculated activity coefficients for the ions in the water+methanol mixtures, values for {G _t ^o (Co(3Rpy)₄Cl ₂ ⁺ )–G _t ^o (Cs⁺)} can be determined where G _t ^o is the standard Gibbs free energy of transfer from water to an aqueous mixture. G _t ^o (Cs⁺) from the solvent sorting scale and from the TPTB scale are then used to calculate G _t ^o (Co(3Rpy)₄Cl ₂ ⁺ ). These two sets of values for G _t ^o (Co(3Rpy)₄Cl ₂ ⁺ ) on the differing scales are then inserted into a free energy cycle applied to the bond extension Co(3Rpy)₄Cl ₂ ⁺ (initial state)Co(3Rpy)₄Cl²⁺+Cl^– (transition state) for the solvolysis in water and in water + methanol mixtures to produce values for G _t ^o (Co(3Rpy)₄Cl²⁺) using both scales. Data for the solubilites of [Copy₄Cl₂]₂[ReCl₆] and [Co(4Rpy)₄Cl₂]₂[ReCl₆] have been re-calculated to compare free energies of transfer for these complex cations with those specified above.     

Hexamethylphosphorsäuretriamid als Ligand, 2. Mitt.: Umsetzungen von [Co(HMPT)4]2+ mit Chlorid-, Bromid- und Jodidionen

Zusammenfassung Folgende Koordinationsformen entstehen aus [Co(HMPT)₄]²⁺ bei Zusatz von Halogenidionen in Hexamethylphosphorsäuretriamid (HMPT): [Co(HMPT)₃Cl]⁺, [Co(HMPT)₂Cl₂], [Co(HMPT)Cl₃]^–, [CoCl₄]^2–, [Co(HMPT)₃Br]⁺, [Co(HMPT)₂Br₂] und [Co(HMPT)₃J]⁺.

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Hexamethylphosphoric triamide as a ligand II: Reactions of Co(HMPT)₄ ²⁺ with chloride, bromide, and iodide ions

The following coordination species are formed from [Co(HMPT)₄]²⁺, by addition of halide ions in hexamethylphosphoric triamide (HMPT): [Co(HMPT)₃Cl]⁺, [Co(HMPT)₂Cl₂], [Co(HMPT)Cl₃]^–, [CoCl₄]^2–, [Co(HMPT)₃Br]⁺, [Co(HMPT)₂Br₂] and [Co(HMPT)₃J]⁺.

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V. Gutmann, A. Weisz undW. Kerber, 1. Mitt., Mh. Chem.100, 2096 (1969).     

Kinetics and Thermodynamics of Solvolysis of a Cationic and an Anionic Chlorocobalt (III) Complex in Water–Ethanol Mixtures

Rate constants and derived thermodynamic activation parameters are reported for solvolysis of trans-[Co(3Mepy)₄Cl₂]⁺ and [Co(CN)₅Cl]^3– ions in water-rich mixtures of water with ethanol at various temperatures and are analyzed by initial- and transition-state contributions. The variation of enthalpies and entropies of activation with solvent composition show extrema in composition ranges where the physical properties of the mixtures, influenced by changes in solvent structures, also show extrema. From the application of a free-energy cycle to the process of the initial state going to the transition state, it is concluded for the solvolysis of both complexes that the Co(III) species in the transition state is more stable in water + ethanol mixtures than in the initial state.     

Organosilicon Amine Gels Based on 3-Aminopropyltriethoxysilane, Cobalt(II) or Chromium(III) Clorides, and Triethoxysilane

Organosilicon gels [Co(NH₂R²)₂Cl₂] and [Cr(NH₂R²)₃Cl₃], containing a diaminodichloride complex of cobalt(II) and triaminotrichloride complex of chromium(III) (R² = CH₂CH₂CH₂SiO(OEt)), were synthesized by the hydrolysis of complexes [Co(NH₂R¹)₂Cl₂] (I) and [Cr(NH₂R¹)₃Cl₃] (II) incorporating peripheral triethoxysilyl groups (R¹ = CH₂CH₂CH₂Si(OEt)₃). The coprecipitated [Co(NH₂R²)₂Cl₂] · 4NH₂R³, [Cr(NH₂R²)₃Cl₃] · 6NH₂R³, [Co(NH₂R²)₂Cl₂] · 2SiO₂, and [Cr(NH₂R²)₃Cl₃] ·xSiO₂ · (3 – x)SiHO_1.5 (R³ = CH₂CH₂CH₂SiO_1.5) gels were obtained by cohydrolysis of complexes I and II with 3-aminopropyltriethoxysilane or triethoxysilane. Interaction with SiH(OEt)₃ is accompanied by the decomposition of silicon hydride groups and the formation of tetraethoxysilane derivatives. The heating of dry gels in a flow of argon or oxygen to 600° results in the formation of amorphous silica having a specific surface area 2–467 m²/g and containing crystalline metals, their chlorides, oxides, silicates, or carbides.     

Synthesis and structural studies of Co(II) and Ni(II) complexes of glutaric- and adipic dihydrazides

Glutaric dihydrazide (GDH) and adipic dihydrazide (ADH) have been found to react with Co(II) chloride and Ni(II) chloride and nitrate in ethanolic solution to form complexes of the general empirical compositionsMLCl₂,ML ₂Cl₂ and [NiL ₂(H₂O)₂] (NO₃)₂ whereM=Co(II), Ni(II) andL=GDH,ADH. Tetrahedral geometry has been proposed for 11 complexes of Co(II) and octahedral geometry for the remaining complexes based on measurements of molar conductance, magnetic susceptibility, electronic and ir spectra.

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Synthese und Struktur von Co(II)- und Ni(II)-Komplexen von Glutarsäure- und Adipinsäuredihydraziden

Zusammenfassung Glutarsäuredihydrazid (GDH) und Adipinsäuredihydrazid (ADH) bilden mit Co(II)-Chlorid und Ni(II)-Chlorid bzw.-Nitrat in ethanolischer Lösung Komplexe der generellen ZusammensetzungenMLCl₂,ML ₂Cl₂ und [NiL(H₂O)₂] (NO₃)₂, mitM=Co(II), Ni(II) undL=GDH,ADH. Für 11-Komplexe von Co(II) wird eine tetragonale Geometrie, für alle anderen Komplexe eine oktaedrische Geometrie vorgeschlagen. Die Basis dazu lieferten Messungen der molaren Leitfähigkeit, der magnetischen Suszeptibilität und der UV- bzw. IR-Spektren.

     

Ruthenium(III) and iridium(III) complexes with nicotine

A new chloride-dimethylsulfoxide-ruthenium(III) complex with nicotine trans-[Ru^IIICl₄(DMSO)[H-(Nicotine)]] (1) and three related iridium(III) complexes; [H-(Nicotine)]trans-[Ir^IIICl₄(DMSO)₂] (2), trans-[Ir^IIICl₄(DMSO)[H-(Nicotine)]] (3) and mer-[Ir^IIICl₃(DMSO)(Nicotine)₂] (4) have been synthesized and characterized by spectroscopic techniques and by single crystal X-ray diffraction (1, 2, and 4). Protonated nicotine at pyrrolidine nitrogen is present in complexes 1 and 3 while two neutral nicotine ligands are observed in 4. In these three inner-sphere complexes coordination occurs through the pyridine nitrogen. Moreover, in the outer-sphere complex 2, an electrostatic interaction is observed between a cationic protonated nicotine at the pyrrolidine nitrogen and the anionic trans-[Ir^IIICl₄(DMSO)₂]^¯ complex.     

Kinetics of the solvolysis of [Co(Rpy)4Cl4]+ with R = 4-t-Bu, 3-Me or 3-Et in mixtures of urea with water

Summary The kinetics of the solvolysis of complex ions trans-[Co(Rpy)₄Cl₂]⁺, with R = 4-t-Bu, 3-Me and 3-Et, have been investigated in mixtures formed by adding urea to water, which enhances the dielectric constant and decreases solvent structure. Differential effects of the changes in solvent structure on the initial and transition states are found to be important factors controlling changes in the rate constant with solvent composition. The variation of the enthalpy and the entropy of activation with solvent composition are contrasted with their variations found for the solvolysis of [Co(Rpy)₄Cl₂]⁺ in mixtures where solvent structure is enhanced by additions of a co-solvent to water. The application of a free energy cycle to the process of the initial state going to the transition state suggests that the Co³⁺ cation in the transition state is more stable than the Co³⁺ cation in the initial state in the water + urea mixtures.     

Syntheses and characterization of cobalt(II) and iron(III) complexes with the Schiff basesN-(o-hydroxybenzylidene)-2-aminobenzimidazole andN-(o-hydroxybenzylidene)-2(2′-aminophenyl)benzimidazole

Summary N-(o-hydroxybenzylidene)-2-aminobenzimidazole (HL) andN-(o-hydroxybenzylidene)-2(2-aminophenyl)benzimidazole (HL) react with CoX₂ (X=Cl, Br, or NCS) and FeCl₃ yielding complexes of general formulae [Co(HL)₂X₂], [Co(HL)₂X₂], [FeCl₂(HL)₂] [FeCl₄], and [FeCl₂(HL)₂][FeCl₄]. Moreover, it was possible to isolate the complexes [Co(HL)Br₂] [Co(L)Cl] and [Co(L)Cl]. The complexes were characterized by elemental analyses, i.r. and electronic spectroscopies and conductivity and magnetic measurements at different temperatures.     

The substitution chemistry of RuCp* (temeda)Cl

Summary Halide abstraction from RuCp*(tmeda)Cl (1,tmeda=Me₂NCH₂CH₂NMe₂) with NaBPh₄ in CH₂Cl₂ leads to the formation of the sandwich complex RuCp*(⁶-C₆H₅BPh₃) (2). In the presence of CH₃CN (1 equiv.) and CO, however, the cationic complexes [RuCp*(tmeda)(CH₃CN)]⁺ (3) and [RuCp*(temeda)(CO)]⁺ (5) are obtained. In CH₃CN,tmeda is also replaced giving [RuCp*(CH₃CN)₃]⁺ (4). Complex1 reacts readily with terminal acetylenes HCCR, the products depending on the nature ofR (Ph, SiMe₃,n-Bu, COOEt). Thus, withR=Ph the ruthenacyclopentatriene complex RuCp*(,-C₄Ph₂H₂)Cl (6), withR=SiMe₃ the cyclobutadiene complex Ru(Cp*)(⁴-C₄H₂(1,2-SiMe₃)₂)Cl (7), and withR=n-Bu and COOEt the binuclear complexes (Cp*)RuCl₂(²:⁴-₂-C₄H₂(1,3-R)₂)Ru(Cp*) (8,9) are obtained. Furthermore, with diethyl maleate in the presence of 1 equiv. of LiCl,1 transforms into the new anionic complex Li[Ru(Cp*) (²-C₂H₂(COOEt)₂)Cl₂] (10). X-ray structures of2,3,4,7, and10 are included.

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Substitutionsreaktionen von RuCp*(tmeda)Cl

Zusammenfassung Chloridabspaltung von RuCp*(tmeda)Cl (1,tmeda=Me₂NCH₂CH₂NMe₂) mittels NaBPh₄ in CH₂Cl₂ führt zur Bildung des Halbsandwich-Komplexes RuCp*(⁶-C₆H₅BPh₃) (2), während in Gegenwart von CH₃CN oder CO die beiden kationischen Verbindungen [RuCp*(tmeda)(CH₃CN)]⁺ (3) und [RuCp*(tmeda)(CO)]⁺ (5) entstehen. In CH₃CN als Lösungsmittel wird sogartmeda unter Bildung von [RuCp*(CH₃CN)₃]⁺ (4) verdrängt. Komplex1 reagiert sehr leicht mit terminalen Alkinen HCCR, wobei die Produkte stark von der Natur des SubstituentenR (Ph, SiMe₃,n-Bu, COOEt) abhängen. Im Fall vonR=Ph entsteht der Ruthenacyclopentatrien-Komplex RuCp*(-C₄Ph₂H₂)Cl (6), mitR=SiMe₃ der Cyclobutadien-Komplex Ru(Cp*)(⁴-C₄H₂(1,2-SiMe₃)₂)Cl (7), und im Fall vonR=n-Bu und COOEt bilden sich die binuklearen Komplexe (Cp*)RuCl₂(²:⁴-₂-C₄H₂(1,3-R)₂)Ru(Cp*) (8,9). Überdies reagiert1 mit Maleinsäurediethylester in Gegenwart von LiCl zum neuen anionischen Komplex Li[Ru(Cp*) (²-C₂H₂(COOEt)₂)Cl₂] (10). Von2,3,4,7 und10 wurden die Kristallstrukturen bestimmt.

     

Formation and isomerisation of theO-sulphito complex of 1,4,7,10,13-penta-azacyclohexadecanecobalt(III)

Summary Dissolved SO₂ reacts rapidly with [Co([16]aneN₅)OH]²⁺ to give [Co([16]aneN₅OSO₂]⁺([16]aneN₅=1,4,7,10, 13-penta-azacyclohexadecane), which on immediate acidification loses SO₂ to give [Co([16]aneN₅)OH₂]³⁺. The O-bonded sulphito complex (_max 526 nm) undergoes a slow linkage isomerisation to give the S-bonded species [Co([16]aneN₅)SO₃]⁺ (_max 466 nm), rather than an internal redox reaction. The S-bonded complex has been isolated and characterised as the perchlorate salt [Co([16]aneN₅) (SO₃H)](ClO₄)₂.     

Synthesis and Structure of Different-Metal Different-Ligand Germanium(IV) and Cobalt(II) or Copper(II) Complexes with 1-Hydroxyethylidenediphosphonic Acid and 1,10-Phenanthroline

Different-metal different-ligand complexes [{Co(Phen)₃}₂{Co(Phen)(H₂O)₄}₂][{Ge(μ-OH)(μ- Hedp)}₆Cl₂] (I), [{Cu(Phen)₂(H₂O)}₂(HPhen)₂][Ge(μ-OH)(μ-Hedp)]₆ · 20H₂O (II) (H₄Hedp = 1-hydroxyethylidenediphosphonic acid, Phen = 1,10-phenanthroline) were synthesized and studied by X-ray diffraction. According to X-ray diffraction data (CIF files CCDC nos. 1573112 (I), 1573113 (II)), compounds I and II are cation–anion type complexes in which the anions are represented by {[Ge(μ-OH)(μ-Hedp)]⁶}^6– and, in the case of I, two additional Cl^– ions, while the cations are [Co(Phen)₃]²⁺, [Co(Phen)(H₂O)₄]²⁺ in I and [Cu(Phen)₂(H₂O)]²⁺, HPhen⁺ in II. In the crystals of compounds I and II, the cations, anions, and water molecules are combined by numerous intermolecular hydrogen bonds, giving rise to a 3D network.     

(18-Crown-6)potassium tetrachloroferrate(III), dibromodichloroferrate(III), and tetrabromoferrate(III): Synthesis and crystal structures

Three new crystalline complexes are synthesized: [K(18-crown-6)]⁺ · An, where An = [FeCl₄]^?(I), [FeBr₂Cl₂]^? (II), and [FeBr₄]^? (III). The crystals of compounds I–III are cubic and isomorphic, space group Fd $ \bar 3 Three new crystalline complexes are synthesized: [K(18-crown-6)]⁺ · An, where An = [FeCl₄]⁻(I), [FeBr₂Cl₂]⁻ (II), and [FeBr₄]⁻ (III). The crystals of compounds I–III are cubic and isomorphic, space group Fd (Z = 16): a = 20.770(2) ? for I, 20.844(3) ? for II, and 20.878(4) ? for III. Structures I–III are solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.047 (I), 0.059 (II), and 0.098 (III) for all 680 (I), 684 (II), and 686 (III) independent reflections. In two tetrahedral anions [Fe(1)X₄]⁻ and [Fe(2)X₄]⁻ in structures I–III, all halogen atoms (X = Cl and Br) are randomly disordered over three close positions relative to the crystallographic axes 3. Structures I–III contain the [K(18-crown-6)]⁺ host-quest complex cation. The K⁺ cation (CN = 8) resides in the cavity of the 18-crown-6 ligand and coordinated by its six O atoms and two disordered halogen X atoms. The coordination polyhedron of the K⁺ cation in complexes I–III is a distorted hexagonal bipyramid. Original Russian Text ? A.N. Chekhlov, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 9, pp. 1566–1570.     

New bipyridyl/phenanthroline ruthenium(II) and ruthenium(III) complexes possessing acetate appended thioether. Evidence for oxidative linkage isomerization

The acetate bearing dithioether, sodium di(2-carboxymethylsufanyl)maleonitrile, L¹ upon reaction with [Ru^II(bpy)₂Cl₂]·2H₂O, [Ru^II(phen)₂Cl₂]·2H₂O, [Ru^III(bpy)₂Cl₂]⁺ or [Ru^III(phen)₂Cl₂]⁺ in methanol formed complexes of the type [(bpy)₂Ru{S₂(CH₂COO)₂C₂(CN)₂}], (1), [(phen)₂Ru{S₂(CH₂COO)₂C₂(CN)₂}], (2), [(bpy)₂Ru{(OOCCH₂)₂S₂C₂(CN)₂}]⁺, (5) and [(phen)₂Ru{(OOCCH₂)₂S₂C₂(CN)₂}]⁺, (6) respectively. Four other Ru(III) complexes with di(benzylsulfanyl)maleonitrile, L², [(bpy)₂Ru{S₂(PhCH₂)C₂(CN)₂}]³⁺, (7) and [(phen)₂Ru{S₂(PhCH₂)₂C₂(CN)₂}]³⁺, (8), and with acetate, [(bpy)₂Ru(OOCCH₃)₂]⁺, (9) and [(phen)₂Ru(OOCCH₃)₂]⁺, (10) were also synthesized. In the cyclic voltammetry, complexes (1) and (2) exhibited quasireversible oxidation waves at 1.01 and 1.02 V vs. Ag/AgCl over GC electrode in DMF, while the corresponding Ru(III) L¹ complexes (5) and (6) exhibit reversible oxidation at E_1/2 0.59 and 0.58 V, respectively, under identical conditions. This is unlike the voltammetric behavior of the Ru(II) and Ru(III) L² complexes, wherein the complex pairs (3), (7) and (4), (8) exhibited identical voltammograms with single reversible one electron waves at E_1/2 0.98 and 0.92 V, respectively under identical conditions. The voltammograms of Ru(II)-L² complexes (3) and (4) also became irreversible in presence of nearly four molar equivalent of sodium acetate. Hence, the irreversible redox behavior of complexes (1) and (2) has been interpreted in terms of rapid linkage isomerization, i.e. shift in κ²-S,S′ to κ²-O,O′ coordination, following the Ru(II)/Ru(III) electrode process. The electronic spectra of Ru(III)-L¹ complexes (5) and (6) resemble closely with that of (9) and (10) instead of Ru(III)-L² complexes (7) and (8), further supports proposed linkage isomerization. The cationic complexes were obtained as [PF₆]⁻ salts and all compounds were characterized using analytical and spectral (IR, ¹H NMR, UV-vis and mass) data.