μ-Nitro-μ-hydroxo-bis(tetramminkobalt(III))-Komplexe

The preparation and the properties of 7 salts containing the complex cation [Co₂{NO₂, OH}(NH₃)₈]⁴⁺ are described. Furthermore, a di-μ-hydroxo complex of the composition [Co₂{OH}₂NO₂(NH₃)₇](ClO₄)₃ · H₂O has been prepared.     

Di-μ-sulfato-μ-hydroxo-bis[triamminkobalt(III)]- und Di-μ-selenato-μ-hydroxo-bis[triamminkobalt(III)]-Komplexe

Preparation and properties of two new complexes containing the cations [Co₂{(SO₄)₂(OH)}(NH₃)₆]⁺ and [Co₂{(SeO₄)₂(OH)}(NH₃)₆]⁺ are described. The absorption spectra in the infrared. visible and ultraviolet region are reported and discussed.     

μ-Nitro-di-μ-hydroxo-bis[trinitro-kobaltat(III)]-Komplexe

4 complexes containing the anion [Co₂{NO₂(OH)₂}(NO₂)₆]^3? are described. The infrared and Raman spectra are reported and discussed.     

Mehrkernige Kobaltkomplexe: Die Struktur von Bis(tri-μ-hydroxo-bis{triamminkobalt(III)}) trisdithionat

Polynuclear Cobalt Complexes: The Structure of Bis(tri-μ-hydroxo-bis{triammine-cobalt(III)})trisdithionate The binuclear complex [(NH₃)₃Co · μ(OH, OH, OH) · Co(NH₃)₃]₂(S₂O₆)₃ crystallizes in the monoclinic space group P2₁/c with lattice constants a = 10.970, b = 9.412, c = 16.069 Å and β = 117.10°. The unit cell contains four cations and six anions. The structure has been determined by an X-ray crystallographic analysis and was refined to R = 0.052.     

Über Reaktionen oxygenierter Kobalt(II)-Komplexe. V. Reaktivität diastereoisomerer μ-Peroxo-μ-hydroxo-dikobalt(III)-Ionen

On Reactions of oxygenated Cobalt(II) Complexes. V. Reactivity of diastereoisomeric μ-peroxo-μ-hydroxo-dicobalt(III) Ions The kinetics of dissociation of μ-peroxo-μ-hydroxo-dicobalt(III) chelates have been reinvestigated using a stopped flow technique. The binuclear cations [(trien)Co(O₂, OH) Co(trien)]³⁺, [(tren)Co(O₂, OH)Co(tren)]³⁺ and [(en)₂Co(O₂, OH)Co(en)₂]³⁺ dissociate on acidifying to Co²⁺ and the protonated ligand and up to 100% of the bound O₂ is evolved. The dissociation is H⁺-catalyzed and first order in complex. The observed rate constants at pH 2 are in the range of 10^?3 to 10^?1 s^?1 (20°). They depend not only on the nature of the ligand and on ligand configuration but also on the diastereoisomeric structure of the binuclear cation. In the case of trien there are 8 possible chemically different isomers. On oxygenation of Co(trien)²⁺ in dilute solution 3 of those isomers seem to be formed preferentially. Their rate constants are separated over a factor of 50. For [(en)₂ Co(O₂, OH)Co(en)₂]³⁺ there exist a meso form and a chiral structure. On oxygenation of Co(en)₂²⁺ in dilute solution the meso form and the racemate are formed to about equal amounts. The racemate dissociates about 5 times slower. Of the 3 possible achiral isomers of [(tren)Co(O₂, OH)Co(tren)]³⁺ one is formed stereoselectively by oxygenation in solution.     

Die Kristall- und Molekülstruktur von μ-5-Pyrimidincarboxylato (O,O′)-di-μ-hydroxo-bis[triamminkobalt(III)]perchlorat

Crystal and Molecular Structure of μ-5-Pyrimidinecarboxylato(O,O′)-di-μ-hydroxo-bis-[triamminecobalt(III)]perchlorate μ-5-Pyrimidinecarboxylato(O,O′)-di-[μ-hydroxo-bis(triamminecobalt)(III)]perchlorate, [(NH₃)₃Co-μ(OH, OH, C₅H₄N₂O₂)Co(NH₃)₃](ClO₄)₄, crystallizes in the orthorhombic space group Ibca with a = 12.686, b = 13.079, c = 31.785 Å and Z = 8 formula units. The complex cation adopts C₂ symmetry, but no mirror plane is present. The Co? Co separation in the binuclear complex is 2.794 Å. The four-membered ring defined by the two Co atoms and the bridging oxygens is folded along the O? O axis, the interplanar angle being 154°. One of the ClO₄ tetrahedra is disordered over two sites in the crystal.     

Die Kinetik und der Mechanismus der Reduktion zweier isomerer μ-Cyanobenzoato-di-μ-hydroxo-bis [triamminkobalt(III)] Komplexe mit Chrom(II) und Vanadin(II)

Kinetics and Mechanisms of the Reductions of Two Isomeric μ-Cyanobenzoato-di-μ-hydroxo-bis[triamminecobalt(III)] Complexes by Cr^II and V^II The Cr²⁺ and V²⁺ reductions of the binuclear μ-3-cyanobenzoato-di-μ-hydroxo-bis[triamminecobalt(III)] and its μ-4-cyanobenzoato analog have been studied by conventional spectrophotometric methods at 25°C, I = 1.0 M (LiClO₄). The reactions are first order in oxidant and reductant, and independent of acid ([H⁺] = 0.04–0.97 M). Reduction of the first cobalt is rate determining. Outersphere mechanisms for all reductions are assigned on the basis of k_Cr : k_V ratios (～0.02). The non capacity of cyanobenzoic acids to mediate electrons via an innersphere mechanism (at least for Cr²⁺ reductions) with attack of reductant at the remote nitrogen atom of the organic ligand is interpreted in terms of the non reducibility of the uncomplexed ligands.     

Reaktion oxygenierter Kobalt (II)-Komplexe. XII. Über einen binuclearen μ-Peroxodikobalt (III)-Komplex mit makrocyclischem Brückenring

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 Co^II 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.     

Kalium-μ-dithio-bis(pentacyanokobaltat(III)) und Kalium-μ-diseleno-bis(pentacyanokobaltat(III))

Potassium-μ-dithio-bis(pentacyanocobaltate(III)) and Potassium-μ-diseleno-bis(pentacyanocobaltate(III)) The oxidation of [Co(CN)₅]^3? by sulfur or selenium leads to the complexes [Co₂S₂(CN)₁₀]^6? and [Co₂Se₂(CN)₁₀]^6?, respectively, which have been isolated as potassium salts K₆[Co₂S₂(CN)₁₀] · 4 H₂O and K₆[Co₂Se₂(CN)₁₀] · 5 H₂O. The μ-dithio complex has also been formed from [Co(CN)₅]^3? with polysulfide, from [CoOH(CN)₅]^3? with H₂S + O₂ and from [Co₂O₂(CN)₁₀]^6? with H₂S. As shown by their vibrational spectra the new complexes contain bridges Co? S? S? Co and Co? Se? Se? Co, respectively.     

Über Reaktionen oxygenierter Kobalt(II)-Komplexe. IX. Oxydative Eigenschaften von Tetrakis(äthylendiamin)-μ-peroxo-μ-hydroxo-dikobalt(III)

Reactions of oxygenated cobalt(II) complexes. IX. Oxidative properties of tetrakis(ethylenediamine)-μ-peroxo-μ-hydroxo-dicobalt(III)

1 VIII s. [1].

[(en)₂Co(O₂, OH)Co(en)₂]³⁺ ( a ) reacts with I^? in acidic aqueous solution according to: Co^III(O₂, OH)Co^III + 21^? + 5H⁺ ? 2Co^III + 3H₂O + I₂. Using I^? in excess first order rate constants are obtained which, to a first approximation, are independent of [I^?]. Comparison with kinetic data of deoxygenation of [(en)₂Co(O₂, OH)Co(en)₂]³⁺ under analogous conditions suggests that both reactions have the same rate determining step. The singly bridged species [(en)₂(H₂O)CoO₂Co(H₂O) (en)₂]⁴⁺ is shown to be the reactive intermediate in the iodide oxidation (Schema 2).     

Über Reaktionen oxygenierter Kobalt(II)-Chelate. VII. Zur Stabilität einfach und doppelt verbrückter μ-Peroxo-dikobalt(III)-Komplexe

On reactions of oxygenated Cobalt(II) Chelates. VII. Stability of mono and doubly bridged μ-Peroxo-dicobalt(III) Complexes. The oxygen carrier properties of the cobalt(II) chelates of symmetrical diethylenetriamine-4-acetic acid (dtma) and unsymmetrical ethylenediamine-1,1-diacetic acid (edda) have been investigated by O₂ equilibrium measurements in alkaline solution. Maximum O₂ uptake is at pH = pK_H (4), indicating that μ-peroxo-μ-hydroxodicobalt(III) ion is the only oxygenated species formed in aqueous solution. Relationships between stability and structural factors are discussed.     

Die Molekül- und Kristallstruktur von Di-μ-sulfato-μ-hydroxo- bis[triamminkobalt(III)]sulfat-8-Hydrat

The crystal structure of Di-μ-sulfato-μ-hydroxo-bis[triamminecobalt(III)] sulfate 8-hydrate has been determined from three-dimensional x-ray data collected by counter techniques. The structure was refined using 2515 independent reflections and the refinement converged to a conventional R factor (on F) of 3.8%. The compound crystallizes in the monoclinic space group C—P2/a, a = 14.122(9), b = 9.858(2), c = 18.81(2) Å, β = 139.3(4), Z = 2, d_obsd = 2.086 g/cm³ and d_calc = 2.14 g/cm³. Within the cation two bidentate SO₄-ligands form bridges between two cobalt atoms. There are two types of S? O bonds (1.50 Å endocyclic, 1.45 Å exocyclic).     

Über Eisen(III)-Komplexe mit Phenolen. IV. Säurekonstanten einiger Polyphenole

The apparent acid constants of some polyphenols and of derivates from salycilic acid are determined by potentiometry using glass or hydrogen electrodes and by UV spectrophotometry on comparable conditions respectively. Anaerobic manipulations were strictly used to avoid autoxidation. The results can be interpreted qualitatively, if the possibility of the formation of intramolecular hydrogen bridges is considered besides the effects of substituting groups.     

Über Alkali-hexachlorochromate(III): Na3CrCl6

Alkali-hexachlorochromates(III): Na₃CrCl₆ X-ray investigations on single crystals yielded for Na₃CrCl₆ a trigonal structure: space group P3 1c; a = 682.0(3) pm; c = 1203.4(5) pm; Z = 2. In a hexagonal-close arrangement of Cl^? ions, 2/3 of the octahedral holes are occupied orderly by Na⁺ and Cr³⁺ ions. The Na compounds of V³⁺ and Mo³⁺ are isotypic. The chlorochromates with K and Rb are crystallizing with the K₃MoCl₆ structure according to X-ray photos of powders. The alkali metal ions habe the C.N. 8 or 11 related to the chloride ions. These compounds and elpasolithes A₂BCrCl₆ (A = Cs? K; B = Rb? Na) can be treated in the same way with the concept of tolerance factors as it is known for the chloro-perovskites AMCl₃. For all compounds the temperatures of phase transitions were determined by DTA. Some structures could be solved from high-temperature-Guinier-patterns, by comparing them with patterns of substances with known structures.     

Über neue Hexafluoroaluminate(III)

On New Hexafluoroaluminates (III) Due to Guinier-Simon powder photographs we obtained by heating mixtures of binary fluorides in a closed system 15 hitherto unknown cubic, colourless Elpasolithes. Cs₂AgAIF₆ crystallizes hexagonal in the Cs₂NaCrF₆-type of structure, but at high pressure conditions (p = 60 kbar) cubic as an Elpasolithe. The Madelung Part of Lattice Energy, MAPLE, is calculated and discussed.     

Dimere low-spin Eisen(III)-Phthalocyanine: Synthese und Eigenschaften ferromagnetisch gekoppelter μ-Oxodi(acidophthalocyaninatoferrate(III))

Dimeric Low-Spin Iron(III) Phthalocyanines: Synthesis and Properties of Ferromagnetically Coupled μ-Oxodi(acidophthalocyaninatoferrates(III)) μ-Oxodi(phthalocyaninatoiron(III)) ([(FePc^2?)₂O]) dissolved in pyridine reacts with different Tetra(n-butyl)ammonium salts yielding partly solvated Di(tetra(n-butyl)ammonium)-μ-oxodi(acidophthalocyaninatoferrates(III)) ((ⁿBu₄N)₂[(Fe(X)Pc^2?)₂O]; X^? = CN^?, Im^?, NCO^?, NCS^?, NO₂^?). The uv-vis. spectra show the typical B, Q, N and L regions of the Pc^2? ligand scarcely influenced by the axial ligands X. In comparison with [(FePc^2?)₂O] mainly the B region is hypsochromically shifted due to strong excitonic coupling (> 3 kK). Two regions of weak absorbance at ca. 7.6–8.7 and 11.4–13.0 kK are assigned to trip-doublet transitions. The m.i.r. and resonance Raman spectra are dominated by the fundamental vibrations of the Pc^2? ligand being characteristic for hexa-coordinated low-spin Fe^III phthalocyanines. Internal vibrations of the ambident axial ligands X are in accordance with the proposed Fe? X bond. The i.r. active asym. (Fe? O? Fe) stretching vibration is observed in the region 631–690 cm^?1. Fe? X stretching vibrations are only present in the f.i.r. spectra. The magnetic properties and Mößbauer spectra are interpreted in terms of an electronic model which assumes that a S′ = 1 ground state arises from strong ferromagnetic coupling of the low-spin Fe^III centres. Both spin-Hamiltonian and ligand-field models have been employed to fit the variable temperature susceptibility data. These low-spin μ-oxo Fe^III dimers are rare compared to the many known examples of coupled high-spin species including the parent, [(FePc^2?)₂O].     

Über Eisen(III)-Komplexe mit Phenolen. V. Komplexbildung mit 4,5-Dibrombrenzcatechin-disulfonsäure(3,6)

The chelate formation between Fe³⁺ and 4.5-dibromopyrocatechol-3.6-disulfonic acid in aqueous solution has been investigated spectrophotometrically. The stability constants and the light absorption properties of the chelates are communicated. Compared with the bromine-free tiron, the ? values increase and the λ_max positions are shifted bathochromically on halogenation. However, due to the changed position of the sulfo groups, the bond-weakening effect of the halogen substituents is covered, leading to a distinct increase of pK_S1, but to only slight alterations of all the other constants. Poor solubility and accessability of the chelating reagent hinder its application in analysis.