Stability of the valinomycin-rubidium complex in water saturated nitrobenzene

From the extraction experiments and -activity measurements, the extraction constant corresponding to the Rb⁺(aq)+CsL⁺(nb)RbL⁺(nb)+Cs⁺(aq) equilibrium in the two-phase water-nitrobenzene system (L=valinomycin; aq=aqueous phase, nb=nitrobenzene phase) was evaluated in the form logK _ex (Rb⁺, CsL⁺)=0.9. Further, the stability constant of the valinomycin-rubidium complex in nitrobenzene saturated with water was calculated as log _nb(RbL⁺)=11.7.     

Extraction of silver into nitrobenzene using cesium dicarbollylcobaltate in the presence of 18-crown-6

From several cesium distribution experiments with ¹³⁴ Cs tracer, the exchange extraction constant corresponding to the equilibrium Ag⁺ (aq)+CsL⁺ (nb)AgL⁺ (nb)+Cs⁺ (aq) in the two-phase water-nitrobenzene system (L = 18-crown-6; aq = aqueous phase, nb = nitrobenzene phase) was determined as log K _ex (Ag⁺ ,CsL⁺ ) = -0.6±0.1. Furthermore, the stability constant of the silver — 18-crown-6 complex in nitrobenzene saturated with water was evaluated for a temperature of 25 °C: log _nb (AgL⁺ ) = 8.2±0.1. Finally, the individual extraction constant of the species AgL⁺ in the water-nitrobenzene system corresponding to the equilibrium AgL⁺ (aq)AgL⁺ (nb) was calculated: K _AgL+ = O1.2±0.1.     

Extraction of sodium picrate into nitrobenzene in the presence of dicyclohexyl-18-crown-6

From extraction experiments and -activity measurements, the extraction constant corresponding to the equilibrium Na⁺(aq)+A^–(aq)+L(nb)NaL⁺(nb)+A^–(nb) taking place in the two-phase water-nitrobenzene system (A^–=picrate, L= dicyclohexyl-18-crown-6; aq-aqueous phase, nb=nitrobenzene phase) was evaluated as logK _ex(NaL⁺, A^–)=2.6.Further, the stability constant of the dicyclohexyl-18-crown-6-sodium complex in nitrobenzene saturated with water was calculated: _nb(NaL⁺)=7.8.     

Stability of dicyclohexyl‐18‐crown‐6‐hydrogen complex in nitrobenzene saturated with water

From extraction experiments with 22 Na as a tracer, the extraction constant corresponding to the equilibrium H⁺ (aq)+NaL ⁺(nb) HL⁺ (nb)+Na ⁺ (aq) in the twophase waternitrobenzene system (L = dicyclohexyl18crown6; aq = aqueous phase, nb = nitrobenzene phase) wasevaluated in the form log K ex (H⁺ , NaL⁺ ) = 0.2. Further, the stability constant of the complex HL⁺ in nitrobenzene saturated with water wascalculated for a temperature of 25 °C : log bnb (HL⁺ ) = 7.7.     

Extraction of Pb2+ with sodium dicarbollylcobaltate in the presence of 15-crown-5

From extraction experiments with ²² Na as a tracer, the exchange extraction constant corresponding to the equilibrium Pb²⁺ (aq)+2 NaL⁺ (nb)PbL₂ ²⁺ (nb)+2 Na⁺ (aq) in the two-phase water-nitrobenzene system (L = 15-crown-5; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K_ex (Pb²⁺ , 2NaL⁺ ) = 4.7±0.1. Moreover, the stability constant of the complex PbL₂ ²⁺ in nitrobenzene saturated with water was calculated for a temperature of 25 °C as log _nb (PbL₂ ²⁺ ) = 17.9±0.1.     

Distribution of Strontium in the System Water — Ca(NO3)2 — Nitrobenzene — Strontium Dicarbollylcobaltate — 18-crown-6

From several strontium distribution experiments with ⁸⁵Sr tracer, the extraction constant corresponding to the equilibrium Ca²⁺(aq)+SrL²⁺(nb) CaL²⁺(nb)+Sr²⁺ (aq) in the two-phase water-nitrobenzene system (L = 18-crown-6; aq = aqueous phase, nb = nitrobenzene phase) was tentatively evaluated as log K _ex (Ca²⁺,SrL²⁺) = –1.9±0.1. Furthermore, the stability constant of the calcium — 18-crown-6 complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log _nb(Cal²⁺) = 10.1±0.1.     

Stability of Complexes of NH4 + with 18-Crown-6, Dicyclohexyl-18-Crown-6, Dibenzo-18-Crown-6 and Dibenzo-24-Crown-8 in Water Saturated Nitrobenzene

From extraction experiments with ²²Na tracer, the exchange extraction constants corresponding to the NH₄ ⁺(aq) + NaL⁺ (nb)NH₄L⁺(nb) + Na⁺ (aq) equilibrium taking place in the two-phase water-nitrobenzene system (L = 18-crown-6, dicyclohexyl-18-crown-6, dibenzo-18-crown-6 and dibenzo-24-crown-8; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the NH₄L⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the order dibenzo-24-crown-8 (DB24C8) < dibenzo-18-crown-6 (DB18C6) < dicyclohexyl-18-crown-6 (DCH18C6) < 18-crown-6 (18C6).     

Extraction of barium picrate into nitrobenzene in the presence of benzo-15-crown-5

From extraction experiments with ¹³³Ba as a tracer, the extraction constant corresponding to the equilibrium Ba²⁺(aq) + 2A^-(aq) + 2L(nb) BaL₂ ²⁺(nb) + 2A^-(nb) in the two-phase water-nitrobenzene system (A^- = picrate, L = benzo-15-crown-5; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K _ex (BaL₂ ²⁺, 2A^-) = 5.7. Furthermore, the stability constant of the benzo-15-crown-5 - barium complex in nitrobenzene saturated with water was calculated: log b_nb (BaL₂ ²⁺) = 14.6.     

Reaction of the Hexa-1,3,5-triyne Me3SiC≡CC≡CC≡CSiMe3 with Ru4(CO)13(μ 3-PPh): Parallels with the Chemistry of Alkynes and Diynes

Reaction of Ru₄(CO)₁₃(₃-PPh) (1) with the 1,3,5-hexatriyne Me₃SiCCCCC CSiMe₃ under mild thermal conditions affords initially Ru₄(CO)₁₀(-CO)₂{₄-¹,¹,²-P(Ph)C(CCSiMe₃)C(CCSiMe₃) (2), via the facile formation of a P–C bond in a manner similar to that demonstrated previously with alkynes and diynes. The 62-CVE cluster 2 readily decarbonylates to give crystallographically characterised Ru₄(CO)₁₀(-CO)(₄-PPh){₄-¹,¹,²,²-Me₃SiCCC₂CCSiMe₃} (3). Attempts to further incorporate the pendant alkyne moieties in 3 into the Ru₄ coordination environment were partially successful with Ru₄(CO)₁₀(₄-PPh)(₄-¹,¹,³,³-RC₄R') (4, R/R'=SiMe₃/CCSiMe₃) being formed as a minor product together with the unusual toluene coordinated species Ru₄(CO)₇(⁶-C₆H₅Me)(₄-PPh)(₄-¹,¹,³,³-Me₃SiC₄CCSiMe₄) (5). Cluster 3 reacts with an excess of Me₃SiCCCCCCSiMe₃ to give the open chain cluster Ru₄(CO)₉(₃-PPh){₄-²,²,⁴,⁴,-C₄(CCSiMe₃)(SiMe₃)C₄(CCSiMe₃)₃} (6).     

Iron Catalysis of SO2 Oxidation in the Atmosphere

The mechanisms of SO₂ oxidation catalyzed by iron ions in the droplet phase of the convective cloud in the lower atmosphere were examined. The relations of the catalytic SO₂ decrease to the concentration of the iron ions and to the intensity of fluxes to the droplet of the OH _(g) and HO _2(g) radicals were characterized. The determining role of the replacement of the low-reactive HO _2(g)(O^– _2(aq)) radical by the reactive SO^– _5(aq) radical in the sulfite medium during daytime was revealed. This process occurred due to the coupling of the decay of the radicals and their regeneration in the liquid-phase reactions O^– _2(aq) + FeOH²⁺ _(aq) Fe²⁺ _(aq) + OH^– _(aq) + O_2(aq), HSO^– _5(aq) + Fe²⁺ _(aq) FeOH²⁺ _(aq) + SO^– _4(aq)HSO ₃ ^- _(aq),O_{2 (aq)} SO^– _5(aq).     

Separation of Cs and Sr using polyoxonium compounds

Extraction separation and concentration of Cs and Sr from aqueous solutions, containing macroconcentrations of competitive ions (Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Al³⁺, Fe³⁺) by the nitrobenzene solutions of bis-1,2-dicarbollylcobaltate in the presence of linear and cyclic polyoxonium compounds (POC) has been investigated. It has been found, that the addition of DB18C6 increases the distribution ratio of cesium (D_cs) but the addition of other crowns and PEG decreases D_Cs value and selectivity of D_Sr and the selectivity of Sr/Ca separation. Separation factors of Sr/Ca increase from (Sr/Ca)2 (found in the absence of POD) to (Sr/Ca)50 (for DB18C6), (Sr/Ca)100 (for 18C6 and DCH18C6) and (Sr/Ca)1000 for 15C5.     

Transfer activity coefficient of the proton in water-pyridine mixtures. A comparison of some extrathermodynamic assumptions

Various water-pyridine mixtures have been selected in order to compare several of the most popular extrathermodynamic assumptions involved in the determination of the transfer activity coefficient of the proton, _t(H⁺). Two techniques have been utilized for this purpose: voltammetry [study of the ferrocene, ferricyanide, or thallium(1) systems] and potentiometry at equilibrium (emf measurements of various galvanic cells, including liquid junctions and hydrogen electrode or silver electrode as a test electrode). The assumptions have been classified into various groups [e.g., _t(Z^p+)=_t(Z^q+) or _t(X^–)=_t(Y⁺)], and the values of _t(H⁺) have been experimentally determined in each case. The results vary depending upon the basic assumption (several pH units); less important differences (e.g., 0.5 pH unit) occur within a given group, and this may be assigned to the nature of the reference species chosen. A simple model of solvation has been also examined; the application of the law of mass action to the corresponding equilibrium provides results close to the _t(X^–) =_t(Y⁺)type of assumptions which ultimately leads to most self-consistent results.     

Chemistry on the rhomboidal Ru4 faces of the clusters RU4(CO)13(μ-PR2)2: Novel small molecule,ligand, and skeletal transformations

Tetrametal clusters such as Ru₄(CO)₁₃(-PPh₂)₂ and Ru₄(CO)₁₀(-PPh₂)₄ are 64-electron systems and, with five metal-metal interactions, are formally electron rich. In fact these clusters have unusual rhomboidal (or flat butterfly) structures with three or four elongated Ru-Ru bonds. With molecular orbitals antibonding with respect to metal metal interactions occupied in such clusters, facile two electron oxidation or ligand dissociation processes should occur, giving electron precise molecules. The molecule Ru₄(CO)₁₃(-PPh₂)₂ 1a undergoes a remarkable, reversible transformation upon loss of CO affording (-H)Ru₄(CO)₁₀(-PPh₂)[₄-¹(P),¹(P),¹(P),¹,²-{C₆H₄}PPh]3 a cluster which contains a five coordinate phosphido bridge and an orthometallated ² arene ring. This conversion is reversible under CO. These and other results which will be discussed confirm that M₄ clusters with electrons in excess of the expected EAN rule count may exhibit unusual reactivity. The solid-state CP/MAS and static powder³¹P NMR spectra of some of these clusters exhibit^99/101Ru-³¹P couplings, values of which have been measured for the first time.     

Temperature Dependence of Chloride Complexation for the Trivalent f-Elements

The influence of elevated temperatures on the formation of 1:1 chloro complexes for Eu³⁺ and Am³⁺ are reported. Using a solvent extraction technique, stability constants for the equilibrium M_(aq) ³⁺+Cl_(aq) ^– MCl_(aq) ²⁺ have been measured in the temperature range of 25–75 °C. Modest increases in ₁ are observed, and small positive enthalpies for these reactions are reported. These data are discussed in the context of previous reports for the trivalent lanthanide and actinide chloro systems.     

Solubility of Crystalline Calcium Isosaccharinate

The solubility of calcium isosaccharinate Ca(ISA)₂(c) was determined at 23°C as a function of pH (1–14) and calcium ion molality (0.03–0.52). The similarity of solubility from the over- and undersaturation directions for different equilibration periods indicated that equilibrium in these solutions was reached rapidly (< 7 days) and that these data can be used to develop thermodynamic equilibrium constants. The solubility data were interpreted using the Pitzer ion–interaction model. The logarithms of the thermodynamic equilibrium constants determined from these data were 1.30 for the dominant reaction at pH < 4.5 [Ca(ISA)₂(c) + 2H⁺ Ca²⁺ + 2HISA(aq)], and –2.22 for the dominant reaction at 4.5 [Ca(ISA)₂(c)+ Ca(ISA)₂(aq)]. In addition, the logarithm of the dissociation constant of HISA [HISA(aq) ISA- + H⁺] was calculated to be –4.46.     

Bi- and polynuclear organometallic complexes of palladium(II) with 4,4′-bipyridine

Summary Binuclear organometallic palladium complexes of the general formulae Pd₂[-(N-N)]R₂L₄(ClO₄)₂ and Pd₂[-(N-N)]Cl₂R₂L₂ [R = C₆F₅ or C₆CI₅; L = group VB or VIB ligand; (N-N') = 4,4-bipyridine] have been prepared by reacting the ligand (N-N) with compounds of the type Pd₂(-CI)₂R₂L₂ or PdOClO₃RL₂. Furthermore, polynuclear [PdR₂(N-N)]_x (R = Cl, C₆F₅ or C₆Cl₅) type complexes have been obtained by reaction of the ligand (N-N) with PdR₂(tht)₂, whilst treatment of [Pd₂(-CI)₂(C₆F₅)₄](NBu₄)₂ with an excess of (N-N) leads to the polynuclearcis-[Pd(C₆F₅)z(N-N)]_x species. Evidence for the structure of these compounds is obtained from their i.r. spectra.     

Synthesis of Platinum-Triruthenium Clusters Using the Zero-Valent Platinum Reagent Pt(nb)3: X-Ray Crystal Structures of Ru3Pt(CO)11(P-iPr3)2, Ru3Pt(μ-H)(μ3-η3-MeCCHCMe)(CO)9(P-iPr3), Ru3Pt(μ3-η2-PhCCPh)(CO)10(P-iPr3), Ru3Pt(μ-H)(μ4-N)(CO)10(P-iPr3) and Ru3Pt(μ-H)(μ4-η2-NO)(CO)10(P-iPr3)

The complexes Pt(nb)_3-n(P-iPr₃)_n (n=1, 2, nb=bicyclo[2.2.1]hept-2-ene), prepared in situ from Pt(nb)₃, are useful reagents for addition of Pt(P-iPr₃)_n fragments to saturated triruthenium clusters. The complexes Ru₃Pt(CO)₁₁(P-iPr₃)₂ (1), Ru₃Pt(-H)(₃-³-MeCCHCMe)(CO)₉(P-iPr₃) (2), Ru₃Pt(₃-²-PhCCPh)(CO)₁₀(P-iPr₃) (3), Ru₃Pt(-H)(₄-N)(CO)₁₀(P-iPr₃) (4) and Ru₃Pt(-H)(₄-²-NO)(CO)₁₀(P-iPr₃) (5) have been prepared in this fashion. All complexes have been characterized spectroscopically and by single crystal X-ray determinations. Clusters 1–3 all have 60 cluster valence electrons (CVE) but exhibit differing metal skeletal geometries. Cluster 1 exhibits a planar-rhomboidal metal skeleton with 5 metal–metal bonds and with minor disorder in the metal atoms. Cluster 2 has a distorted tetrahedral metal arrangement, while cluster 3 has a butterfly framework (butterfly angle=118.93(2)°). Clusters 4 and 5 posseses 62 CVE and spiked triangular metal frameworks. Cluster 4 contains a ₄-nitrido ligand, while cluster 5 has a highly unusual ₄-²-nitrosyl ligand with a very long nitrosyl N–O distance of 1.366(5) Å.     

Compounds of imidazoles with ruthenium(III) chloride

Summary Reaction of ruthenium(III) chloride with imidazole(Im) and different substituted imidazoles,viz. N-methylimidazole (N-MeIm), 2-methylimidazole(2-MeIm), 4-methylimidazole (4-MeIm),N-vinylimidazole(N-VIm), 2-methyl- 1-vinyl-imidazole(2-Me-1-VIm), 1,2-dimethylimidazole(1,2-Me,Im), 2-ethylimidazole(2-EtIm) and 2-ethyl-4(5)-methylimidazole (2-Et-4(5)-MeIm] yield products of the types [Ru₂L₄Cl₆] · 2 H₂O (L = N-VIm or 4-MeIm), [Ru₂L₄Cl₆] · 4 H₂O (L = Im or 2-Et-4(5)-MeIm), [Ru₂L ³ (H₂O)Cl₆] (L =N-MeIm or 2-MeIm), [Ru₂L ² (H₂O)₂Cl₆] (L = 1,2-Me₂Im or 4-MeIm), [Ru(2-Me-1-VIm)₃Cl₃] · H₂O and [Ru(2-EtIm)₃(H₂O)Cl₂]. These compounds were characterised by elemental analyses, conductometric measurements, i.r. and electronic spectral analyses. Magnetic moments range from 1.01 to 1.9 B.M. The e.s.r. spectra and g values of some of the compounds are indicative of high distortion.     

Transfer chemical potentials for cobalt(III) and chromium(III) complexes from water into aqueous methanol; their relevance to reactivity trends for cobalt(III)-chloride aquation

Summary We report solubilities of a number of cobalt(III) and chromium(III) complex salts in methanol-water mixtures. From these, and published solubilities of salts of other complexes of these metals, we have calculated transfer chemical potentials from water into aqueous methanol for a variety of cationic and anionic complexes of cobalt(III) and chromium(III), using the assumption _m(Ph₄As⁺) + _m(BPh ₄ ^– ). The established trends are discussed in terms of electrostatic factors and of the hydrophilicity or hydrophobicity of the ligands present. The effects of single ion assumptions on conclusions of initial state-transition state analyses of solvent effects on reactivity are assessed with particular reference to aquation of thetrans-[Co(en)₂Cl₂]⁺ andtrans-[Co(py)₄Cl₂]⁺ cations.On leave from the Faculty of Science, Sohag, Egypt.     

Synthesis of Co3(CO)7(μ-η3-Allyl)(μ3-X) Complexes (X=S, Se) and Structure of the Selenium Derivative

The complexes Co₃(CO)₉( ₃-X) (X=S, Se) can be reduced to the corresponding anionic species [Co₃(CO)₉( ₃-X)]^–, which react with allyl bromide to give Co₃(CO)₇(- ³-C₃H₅)( ₃-X) (X=S, Se). These are the first two cobalt complexes containing the bridging - ³-allyl ligand. The structure of the selenium complex was determined by X-ray crystallography. Crystal data for Co₃(CO)₇(- ³-C₃H₅)( ₃-Se) are as follows: space group P2₁/c, a=9.051(2) Å, b=8.102(2) Å, c=21.27(4) Å, =93.82(3)°, Z=4, and R=0.0565 for 2491 observed reflections.