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1.
Polynuclear Cobalt Complexes. II. Preparation and Structure of [(tren) (NH3)Co(O2)Co(NH3) (tren)](SCN)4 · 2H2O The title compound is obtained on oxygenation of [Co(tren)(H2O)2]2+ in 6M aqueous ammonia or by ligand exchange starting from [(NH3)5Co(O2)Co(NH3)5]-(NO3)4. An X-ray structure determination was made. The substance forms monoclinic crystals, space group P21/c, lattice constants a=10,135, b=8,473, c=19,484 Å, β=108,58°, with two formula units in the cell. The final R is 0,066. The binuclear cation has a center of symmetry, so the Co? O? O? Co unit is planar; the Co? O? O angle is 111,5°. The tertiary nitrogen atoms of both chelate groups are cis to the O2 bridge, as found in doubly bridged [(tren)Co(O2,OH)Co(tren)](ClO4)3 · 3H2O. On acidification in solution, the singly bridged cation [(tren) (NH3)CoO2Co(NH3)(tren)]4+ (a) loses the bound O2 completely. But unlike the doubly bridged cation b , the rate of dissociation of a is independent of pH (Fig. 5). At higher pH (8–10) bridging a→b (Fig. 2) occurs. Both reactions must have the same rate determining step, the first order rate constants being of the order of 2 · 10?3 s?1 (25°, 0,35M KCl).  相似文献   

2.
On Reactions of oxygenated Cobalt(II) Chelates. VI. Preparation of diastereoisomeric tetrakis(ethylenediamine)-μ-peroxo-μl-hydroxo-dicobalt(III) Perchlorates Oxygenation of Co(en)22+ leads to a mixture of two isomeric forms of [(en)2Co(O2, OH)-Co(en)2] (ClO4)3 · H2O from which the less soluble meso form can be readily crystallized. Further crystallization from the mother liquor yields the racemate ΔΔ/ΔΔ. The pure racemate may be obtained by either of the following methods: (a) By ligand exchange starting from mono bridged [(NH3)5CoO2Co(NH3)5] (NO3)4 or from doubly bridged [(SCN) (NH3)3Co(O2, OH)Co(NH3)3(SCN)] SCN · 2H2O. (b) By reaction of cis-[Co(en)2(OH2)2]3+ with H2O2. Reaction (b) proceeds via an intermediate cis-[Co(en)2(OOH) (OH2)] (ClO4)2 · H2O which at higher pH reacts with [Co(en)2(OH) (OH2)]2+ to yield the desired doubly bridged ΔΔ/ΔΔ tetrakis(ethylenediamine)-μ-peroxo-μ-hydroxodikobalt(III)-perchlorate.  相似文献   

3.
A novel hydrated cobalt tetraborate complex NH4[Co(NH3)5(H2O)][B4O5(OH)4]2·6H2O, was synthesized by the reaction of NH4‐borate aqueous with CoCl2 and its structure was determined by single crystal X‐ray diffraction. The crystal system of this complex is orthorhombic, the space group is Pnma, and the unit cell parameters are a=1.2901(2) nm, b=1.6817(3) nm, c=1.1368(2) nm, α=β=γ=90°, V=2.4742(8) nm3, and Z=4. This compound contains infinite borate layers constructed from [B4O5(OH)4]2? units via hydrogen bonds. The adjacent polyborate anion layers are further linked together with the octahedral [Co(NH3)5(H2O)]3+ groups through hydrogen bonds to form 3D framework. The groups and guest water molecules are deposited in the empty space of this framework and interact with the layers by extensive hydrogen bonds. Infrared and Raman spectra (4000–400 cm?1) of NH4[Co(NH3)5(H2O)][B4O5(OH)4]2·6H2O were recorded at room temperature and analyzed. Fundamental vibrational modes were identified and band assignments were made. The middle band observed at 575 cm?1 in Raman spectrum is the pulse vibration of [B4O5(OH)4]2?.  相似文献   

4.
Using a new mathematical treatment, the nature and stability constants of the simple and mixed complex-species of copper(II) with hydroxyde and ammonia as ligands have been determined. The solubility curves of CuO in heterogeneous equilibrium have been identified in function of pH only and in function of pH and pNH3tot at 25° and unit ionic strength (NaClO4). The predominent species in the relatively dilute system limited by the ionic strength are [Cu2+], [Cu(OH)2], [Cu(OH)], [Cu(OH)], [Cu(NH3)], [Cu(NH3)], [Cu(NH3)], [Cu(NH3) (OH)+], [Cu(NH3)3(OH)+] and [Cu(NH3)2(OH)2].  相似文献   

5.
Summary The kinetics of reversible complexation of NiII and CoII with iminodiacetato(pentaammine)cobalt(III), [(NH3)5-Co(idaH2)]3+ and NiII with iminodiacetato(tetraammine)-cobalt(III), [(NH3)4Co(idaH)]2+, have been investigated by the stopped-flow technique at 25 °C, pH = 5.7–6.9 and I = 0.3 mol dm –3. The reaction paths (NH3)5Co(idaH)2++M2+(NH3)5Co(ida)M3++H+ (NH3)5Co(ida)++M2+(NH3)5Co(ida)M3+ (NH3)4Co(ida)++Ni2+(NH3)4Co(ida)Ni3+ have been identified (idaH = N+H2(CH2CO2)2H, ida = NH(CH2COO)2–]. The rate parameters for the formation and dissociation of the binuclear species are reported. The data are essentially consistent with an I d mechanism. The dissociation rate constants of the binuclear species indicate that Ni2+ and Co2+ are chelated by the coordinated iminodiacetate moiety.  相似文献   

6.
Reactions of oxygenated cobalt(II) complexes. XII. A binuclear μ-peroxodicobalt(III) complex with a macrocyclic bridging ring
  • 1 XI: siehe [1].
  • Singly bridged [(tren) (NH3) CoO2(NH3) (tren)]4+ reacts with excess tren by replacement of NH3 in cis-position to the peroxo group and formation of a new type of doubly bridged μ-peroxo complex. An X-ray structure determination of [(tren)-Co(O2, tren)Co(tren)] (ClO4)4 · 2 H2O showed that the additional tren forms a macrocyclic bridging ring. The conformation of the CoOOCo group is transoid with a dihedral angle of 20°. The crystals are monoclinic with space group P21/c. The lattice constants are a = 9,798, b = 26,385, c = 16,385 Å, β = 110,2° with four formula units in the cell. The final R value is 0,124. ClO anions are disordered. The reactions of [(tren)Co(O2, tren)Co(tren)]4+ in aqueous solution are compared with those of [(tren) (NH3) CoO2Co (NH3tren)]4+. In acidic solution the new complex mainly decomposes to CoII and O2. In alcaline medium the bridging tren is replaced by an OH bridge, forming the well characterized doubly bridged [(tren)-Co(O2, OH)Co(tren)]3+. Differing from the singly bridged bis (ammino) complex, the reactions of which show no pH dependency at all, the decomposition of the tren bridged complex is H+-catalyzed. The kinetic data have been interpreted as (i) preceding fast protonation step which is followed by a conformational change of the bridging ring, (ii) acid hydrolysis of a Co-μ-tren bond and (iii) fast cleavage of the Co-OO bond which is labilized by coordinated H2O.  相似文献   

    7.
    The solubility of precipitated Cd(OH)2 was determined at 25°C in 1 M NaClO4, as a function of pH and of the ammonia content of the solutions. Formation constants were obtained for the following hydroxo, ammine and hydroxo-ammine complexes: CdOH+, Cd(OH)2, Cd(OH), CdNH, Cd(NH3), Cd(NH3), Cd(NH3) and Cd(OH)2NH3. The solubility product of the hydroxide was also calculated. The presence of polynuclear species was investigated by titrimetric determinations of the hydrogen ion concentration at constant metal concentration.  相似文献   

    8.
    A platinum-lined, flowing autoclave facility was used to investigate the solubility behavior of cobalt(II) oxide (CoO) in deoxygenated ammonium and sodium hydroxide solutions between 22 and 288°C. Co(II) ion activity in aqueous solution was controlled by a hydrous Co(II) oxide when nitrogen was used for deoxygenation and by metallic cobalt when hydrogen was used. Measured cobalt solubilities are interpreted using a Co(II) ion hydroxo- and amminocomplexing model and thermodynamic functions for these equilibria were obtained from a least-squares analysis of the data. A common set of thermodynamic properties for the species Co(OH)+, Co(OH)2(aq) and Co(OH)(NH3)+ is provided to permit accurate cobalt oxide solubility calculations over broad ranges of temperature and alkalinity.  相似文献   

    9.
    The reduction of several Co(III) ammine complexes by various hydroxyalkyl radicals produces Co(II). The reduction with CH2OH and CHOHCH2OH radicals is strongly pH dependent showing G(Co2+)≅ 0.5 at low pH, whereas, quantitative reduction, G(Co2+)≅6.0 occurs at neutral pH. The reduction of [Co(NH3)5X), whereas X = Cl, Br, H2O, by CH2OH is independent of pH. Similarly, the reduction of various Co(III) ammine complexes by CH3CHOH, (CH3)2COH and (CH3CH2CHOH, CH3CHCH2OH) radicals is independent of pH. Little, if any, effect is shown on the variation of G(Co2+) with pH by reducing the dose rate to 50 and 30% of the initial value. Since no protonation/deprotonation of the species involved occurs in the pH range studied, the pH dependence of G(Co2+) values should mean that the reduction proceeds through an inner sphere mechanism as suggested earlier. ĊH2OH + Co(NH3)63+ = [Co(NH3)6CH2OH]3+ = Co2+ + 6NH3 + CH2O + H+  相似文献   

    10.
    The kinetics of electron transfer reactions between [Fe(CN)6]4? and [Co(NH3)5pz]3+ and between [Ru(NH3)5pz]2+ and [Co(C2O4)3]3? was studied in concentrated salt solutions (Na2SO4, LiNO3, and Ca(NO3)2). An analysis of the experimental kinetic data, kobs, permits us to obtain the true (unimolecular) electron transfer rate constants corresponding to the true electron transfer process (precursor complex → successor complex), ket. The variations of both, kobs and ket, with salt concentrations are opposite for these reactions. These opposite tendencies can be rationalized by using the Marcus–Hush treatment for electron transfer reactions. The conclusion is that the negative salt effect found for the first reaction ([Fe(CN)6]4? + [Co(NH3)5pz]3+) is due to the increase of the reaction and reorganization free energies when the concentration of salt increases. In the case of the second reaction ([Ru(NH3)5pz]2+ + [Co(C2O4)3]3?), the positive salt effect observed is caused by the fact that the driving force becomes more favorable when the concentration of salt increases. Thus, it is shown that for anion/cation electron transfer reactions the kinetic salt effect depends on the charge sign of the oxidant (and the reductant). © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 37: 81–89, 2005  相似文献   

    11.
    The stability constants of zirconium(IV) hydrolysis species have been measured at 15, 25, and 35 °C [in 1.0 mol-dm–3 (H,Na)ClO4] using both potentiometry and solvent extraction. In addition, the solubility of [Zr(OH)4(am)] has been investigated in a 1 mol-dm–3 (Na,H)(ClO4,OH) medium at 25 °C over a wide range of –log [H+] (0-15). The results indicate the presence of the monomeric species Zr(OH)3+, Zr(OH)2 2+, Zr(OH)3 +, and Zr(OH)4 0(aq) as well as the polymeric species Zr4(OH)8 8+ and Zr2(OH)6 2+. The solvent extraction measurements required the use of acetylacetone. As such, the stability constants of zirconium(IV) with acetylacetone were also measured using solvent extraction. All stability constants were found to be linear functions of the reciprocal of temperature (in kelvin) indicating that H o and S o are both independent of temperature (over the temperature range examined in the study). The results of the solubility experiments have shown four distinctly different solubility regions. In strongly acidic solutions, the solubility is controlled by the formation of polynuclear hydrolysis species in solution whereas in less acidic solution the formation of mononuclear hydrolysis species becomes dominant. The largest portion of the solubility curve is controlled by equilibrium with aqueous Zr(OH)4 0(aq) where the solubility is independent of the proton concentration. In alkaline solutions, the solubility increases due to formation of the zirconate ion. The middle region was used to determine the solubility constant (log *K s10) of Zr(OH)4(s). From the data in the alkaline region, a value of the stability of the zirconate ion has been determined. This is the first time that the possible evidence for the zirconate ion has been identified in aqueous solution that has previously been found only in the solid phase.  相似文献   

    12.
    The reaction of the ammonia diol [(NH3)4Rh(OH)2Rh(NH3)4]4+with H2O2 Yields among other products a peroxo-bridged dimeric species [(NH3)4Rh(O2)(OH)Rh(NH3)3(H2O)](CIO4)3. Its structure was determined by single-crystal X-ray diffraction. The crystals are monoclinic with space group P21/n and lattice constants a=12.269 (5) Å, b=10.769(4) Å, c=15.964(4) Å, β=107.17(3)°. The dihedral angle of the RhOORh group in the bimetallic ring deviates by 62δ from planarity. The peroxo-bridged complex was found to disproportionate in 1M HCIO4 and a red superoxo-bridged complex. [(NH3)4Rh(O2)(OH)Rh(NH3)3(H2O)](NO3)4, was isolated. Its structure was solved by single-crystal X-ray diffraction. The crystals are orthorhombic with space group Pna 2, and lattice constants a=14.997(5) Å, b=11.952(4) Å, C=10.489(4) Å. The dihedral angle off the RhOORh group deviates by 7δ from planarity.  相似文献   

    13.
    The counter ion in CZE separation systems affects resolution, effective field strength and electroosmosis. Alkali metals (lithium, sodium, potassium, and cesium), the ammonium ion, and several complexes of metals with ammonia ([Ag(NH3)2]+, [Cu(NH3)4]2+, [Zn(NH3)4]2+, [Cd(NH3)4]2+, [Ni(NH3)6]2+, and [Co(NH3)6]2+) have been studied for their effect on the separation of diuretics. With the alkali metals the electroosmotic flow velocity decreased and the effective field strength and resolution increased as the hydrated radius of the alkali metal decreased. All the metal-ammonia complexes except that with silver greatly reduced the electroosmotic flow velocity (Veo) and had only a slight effect on the effective field strength (Eeff). Because these complexes had a negligible effect on the ionic strength of the buffer, they enabled high separating power to be maintained during the separation, and hence the use of more energy in the separation system. This yielded better resolution of the compounds, but the analysis time was then compromised. A simultaneous reduction in capillary length and Veo while maintaining the high voltage enabled increased resolution without an increase in analysis time. The ability to control Veo by adding small concentrations (< 100 μM ) of metal complexes to the buffer solution makes it possible to adjust the analysis time and capillary length independently while employing high separation power.  相似文献   

    14.
    Studies of the stoichiometry and kinetics of the reaction between hydroxylamine and iodine, previously studied in media below pH 3, have been extended to pH 5.5. The stoichiometry over the pH range 3.4–5.5 is 2NH2OH + 2I2 = N2O + 4I? + H2O + 4H+. Since the reaction is first-order in [I2] + [I3?], the specific rate law, k0, is k0 = (k1 + k2/[H+]) {[NH3OH+]0/(1 + Kp[H+])} {1/(1 + KI[I?])}, where [NH3OH+]0 is total initial hydroxylamine concentration, and k1, k2, Kp, and KI are (6.5 ± 0.6) × 105 M?1 s?1, (5.0 ± 0.5) s?1, 1 × 106 M?1, and 725 M?1, respectively. A mechanism taking into account unprotonated hydroxylamine (NH2OH) and molecular iodine (I2) as reactive species, with intermediates NH2OI2?, HNO, NH2O, and I2?, is proposed.  相似文献   

    15.
    The FT IR and FT Raman spectra of Co(en)3Al3P4O16 · 3H2O (compound I) and [NH4]3[Co(NH3)6]3[Al2(PO4)4]2 · 2H2O (compound II) are recorded and analysed based on the vibrations of Co(en)33+, Co(NH3)63+, NH4+, Al---O---P, PO3, PO2 and H2O. The observed splitting of bands indicate that the site symmetry and correlation field effects are appreciable in both the compounds. In compound I, the overtone of CH2 deformation Fermi resonates with its symmetric stretching vibration. The NH4 ion in compound II is not free to rotate in the crystalline lattice. Hydrogen bonding of different groups is also discussed.  相似文献   

    16.
    A platinum-lined flowing autocláve facility was used to investigate the solubility behavior of magnetite (Fe3O4) in alkaline sodium phosphate and ammonium hydroxide solutions between 21 and 288°C. Measured iron solubilities were interpreted via a Fe(II)/Fe(III) ion hydroxo-, phosphato-, and ammino-complexing model and thermodynamic functions for these equilibria were obtained from a least-squares analysis of the data. A total of 14 iron ion species were fitted. Complexing equilibria are reported for 8 new species: Fe(OH)(HPO4), Fe(OH)2(HPO4)2–, Fe(OH)3(HPO4)2–, Fe(OH)(NH3)+, Fe(OH)2(PO4)3–, Fe(OH)4(HPO4)3–, Fe(OH)2(H2PO4), and Fe(OH)3(H2PO4)3–. At elevated temperatures, hydrolysis and phosphato complexing tended to stabilize Fe(III) relative to Fe(II), as evidenced by free energy changes fitted to the oxidation reactions.
      相似文献   

    17.
    Several salts containing the cation Co(penten)3+, in which the hexamin «penten» (formula: page 625) acts as a sexadentate ligand, have been synthesized and characterized. Its optical antipodes have been separated in some of the salts (Fig. 4), and the rate of racemization studied. In strongly alkaline solution one of the 5 chelate rings slowly opens and Co(penten)OH2+ is produced (Fig. 1), to which a first proton can be attached at the terminal NH2-group (→ Co(Hpenten)OH3+), and a second which converts the hydroxo-complex into the aquo-complex (→ Co(Hpenten)OH4+). The equilibria between Co(penten)3+, Co(penten)OH2+, Co(Hpenten)OH3+ and Co-(Hpenten)OH24+ have been elucidated, and the kinetics of the ring opening and ring closing reactions have been studied. Ring opening and ring closure take place with retention of configuration. It proved impossible to open two of the chelate rings of Co(penten)3+. Cristalline salts with cations of the general formula Co(penten)X3?λ or Co (Hpeten)X4?λ, with Xλ? ? OH?, H2O, F?, Cl?, Br?, J?, SCN?, NO2,? and CO32?, have been obtained and characterized (Fig. 1, 2, 7 and Table 1).  相似文献   

    18.
    Properties indirectly determined, or alluded to, in previous publications on the titled isomers have been measured, and the results generally support the earlier conclusions. Thus, the common five‐coordinate intermediate generated in the OH?‐catalyzed hydrolysis of exo‐ and endo‐[Co(dien)(dapo)X]2+ (X=Cl, ONO2) has the same properties as that generated in the rapid spontaneous loss of OH? from exo‐ and endo‐[Co(dien)(dapo)OH]2+ (40±2% endo‐OH, 60±2% exo‐OH) and an unusually large capacity for capturing (R=[CoN3]/[CoOH][]=1.3; exo‐[CoN3]/endo‐[CoN3]=2.1±0.1). Solvent exchange for spontaneous loss of OH? from exo‐[Co(dien)(dapo)OH]2+ has been measured at 0.04 s?1 (k1, 0.50M NaClO4, 25°) from which similar loss from the endo‐OH isomer may be calculated as 0.24 s?1 (k2). The OH?‐catalyzed reactions of exo‐ and endo‐[Co(dien)(dapo)N3]2+ result in both hydrolysis of coordinated via an OH?‐limiting process =153 M ?1 s?1; =295 M ?1 s?1; KH=1.3±0.1 M ?1; 0.50M NaClO4, 25.0°) and direct epimerization between the two reactants =33 M ?1 s?1; =110 M ?1 s?1; 1.0M NaClO4, 25.0°). Comparisons are made with other rapidly reacting CoIII‐acido systems.  相似文献   

    19.
    The vibrational and electronic spectra as well as the magnetic properties of the ion [Co(NH3)4]2+are given and discussed. [Co(NH3)4](ReO4)2 crystallizes cubically and is isostructural with the compounds [Zn(NH3)4](ReO4)2, [Zn(NH3)4](MnO4)2, [Cd(NH3)4](ReO4)2, [Cd(NH3)4](MnO4)2, [Zn(NH3)4]- (OsO3N)2 and [Cd(NH3)4](OsO3N)2.  相似文献   

    20.
    The first structural characterization of the text‐book tetraammineberyllium(II) cation [Be(NH3)4]2+, obtained in the compounds [Be(NH3)4]2Cl4 ? 17NH3 and [Be(NH3)4]Cl2, is reported. Through NMR spectroscopic and quantum chemical studies, its hydrolysis products in liquid ammonia were identified. These are the dinuclear [Be2(μ‐OH)(NH3)6]3+ and the cyclic [Be2(μ‐OH)2(NH3)4]2+ and [Be3(μ‐OH)3(NH3)6]3+ cations. The latter species was isolated as the compound [Be3(μ‐OH)3(NH3)6]Cl3 ? 7NH3. NMR analysis of solutions of BeF2 in liquid ammonia showed that the [BeF2(NH3)2] molecule was the only dissolved species. It acts as a strong fluoride‐ion acceptor and forms the [BeF3(NH3)]? anion in the compound [N2H7][BeF3(NH3)]. The compounds presented herein were characterized by single‐crystal X‐ray structure analysis, 9Be, 17O, and 19F NMR, IR, and Raman spectroscopy, deuteration studies, and quantum chemical calculations. The extension of beryllium chemistry to the ammine system shows similarities but also decisive differences to the aquo system.  相似文献   

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