Synthesis of novel termetallic isopropoxides

Novel termetallic isopropoxides are reported which may be represented by the general formulae: [(PrⁱO)₃M(μ-OPrⁱ)₂Be(μ-OPrⁱ)₂Al(OPrⁱ)₂], [(PrⁱO)₂M(μ-OPrⁱ)₂Be(μ-OPrⁱ)₂Al(OPrⁱ)₂]₂ [where M = Ti(IV), Zr(IV) and Hf(IV)] and [(PrⁱO)₄M(μ-OPrⁱ)₂Be(μ-OPrⁱ)₂Al(OPrⁱ)₂] [where M = Nb(V) and Ta(V)]. Attempts to synthesize derivatives with the general formula, [(PrⁱO)₇M₂(μ-OPrⁱ)₂Be(μ-OPrⁱ)₂Al(OPrⁱ)₂] [where M = Ti(IV), Zr(IV) or Hf(IV)], were unsuccessful and in all such cases a mixture of M(OPrⁱ)₄ and [(PrⁱO)₃M(μ-OPrⁱ)₂Be(μ-OPrⁱ)₂Al(OPrⁱ)₂] was obtained. All these derivatives are soluble in common organic solvents and with the exception of titanium(IV) derivatives, they can be volatilised without noticeable disproportionation. These products have been characterized by elemental analyses, molecular weights, IR, ¹H NMR and (in representative cases) mass spectral studies also.     

Microscopic detection of chromium as chromium(III)

Summary Trisodium phosphate is recommended as a reagent for the microscopic detection of chromium (III). Sensitivity of the test is 6 of chromium (III) in a volume of 0.01 ml. Of particular importance is the fact that aluminum and iron (III) do not react with the reagent to form crystalline precipitates.

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Zusammenfassung Tertiäres Natriumphosphat gibt mit Chrom(III)-Lösungen eine charakteristische Fällung, in der unter dem Mikroskop rechteckige Kristalle zu erkennen sind. Weder Aluminium noch Eisen(III) gibt mit diesem Reagens einen kristallinen Niederschlag. Die Reaktion gestattet den Nachweis von 6 Chrom in 0,01 ml Lösung. Auch Quecksilber(II) gibt charakteristische Kristalle.

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Résumé On recommande le phosphate trisodique comme réactif pour la recherche microscopique du chrome-III. La sensibilité de l'essai est 6 de chrome-III dans un volume de 0,01 ml. Le fait que l'alumine et le fer-III ne se combinent pas avec le réactif pour former des précipités cristallins présente une importance particulière.

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With 2 figures.     

Triamidoamine complexes of chromium(III) and chromium(IV)

Treatment of [CrCl3(THF)3] with slightly more than 1 equiv of Li3(N3N) [(N3N)(3-) = ((Me3SiNCH2CH2)3N)(3-)] affords the triamidoamine complex [Cr(N3N)] (1) in 75% yield. 1 is oxidized by PhICl2, CuCl2, or AgCl to give the chromium(IV) complex [Cr(N3N)Cl] (2) in moderate yields. Alternatively, complex 2 is obtained directly from [CrCl3(THF)3] in 50% yield after treatment with 0.5 equiv of Li3(N3N). Both compounds are high-spin complexes bearing three and two unpaired electrons, respectively. Their molecular structures are described revealing a trigonal monopyramidal and trigonal bipyramidal coordination geometry of the chromium center, respectively.     

Cyclopentadienyl mesityl complexes of chromium(II) and chromium(III)

Chromium(III) mesityl complexes were synthesized by protonolysis of chromocene with 1,3-diisopropylimidazolium chloride or DBU hydrochloride, salt metathesis with MesMgBr, and single electron oxidation with iodine.     

Synthesis and structural studies of novel aminopolychloroethylated chelate acetylacetonate complexes of aluminum (III) and chromium (III)

Structural Chemistry - Novel bio-medicinally promising complexes of amidotrichloroethylated acetylacetonate with Cr(III) and Al(III), which combine synthetically and pharmacologically attractive...     

Oxidation of chromium(III) by alkaline hexacyanoferrate(III)

Alkaline hexacyanoferrate(III) oxidation of freshly prepared solutions of Cr^III (pH>12) at 27°C follows the rate law, Equation 1:

Sorption of chromium(III) and chromium(VI) on lead sulfide

The sorption of chromium(III) and chromium(VI) on lead sulfide has been investigated in dependence on pH, time of sorption and the concentrations of sorbate and sorbent. The mechanisms of the sorption of Cr³⁺ and CrO ₄ ^2– traces on lead sulfide are discussed; a difference between CrO ₄ ^2– sorption on PbS and -Fe₂O₃ has been found. Sulfates and molybdates affect the removal of chromates from aqueous solutions. Lead sulfide carrier prepared in this work was also used for the preconcentration of chromium(III) and chromium(VI) from tap water.     

Sorption of chromium(VI) and chromium(III) on aluminium hydroxide

Factors that influence the sorption of Cr(VI) and Cr(III) on aluminium hydroxide were investigated. The sorption of chromates decreases as the pH of the suspension increases. The mechanism of CrO ₄ ^2– sorption was interpreted in terms of reactions between chromates and –OH and/or H₂O groups at the hydroxide/liquid interface. It has been shown that chromates are more tightly sorbed on aluminium hydroxide compared to other anions, e.g. chlorides. On the other hand, specifically absorbed anions, such as molybdates, compete strongly with chromates for the sorption sites. The sorption of chromium(III) increases with the pH of the suspension. Also, the sorption of chromium(III) is suppressed in the presence of citrate ions. The best conditions for the fixation of Cr(VI) and Cr(III) by aluminium hydroxide are presented.     

2,5-Diphenyloxazole chromium(III) complexes

Summary Complexes of chromium(III) with 2,5-diphenyloxazole (PPO) of general formula Cr(PPO)_nX₃·m H₂O, where X=Cl^–, Br^–, I^– or NO ₃ ^su– ; n=1–3 and m=0–6, have been prepared and studied by spectroscopic and magnetic methods and by molar conductivity measurements. All the complexes seem to be hexacoordinated, generally with monodentate N-bonded ligand.     

The reaction of neodymium(III) oxide with chromium(III) oxide

The reaction of Nd₂O₃ and Cr₂O₃ in air has been studied in the temperature range 350–950°C. The nature and quantity of products formed was investigated primarily by an analytical scheme developed to permit the determination of the amounts of unreacted Nd₂O₃ and Cr₂O₃ and the amounts of possible products. From 350–600°C the sole product was Nd₂(CrO₄)₃, from 630–840°C the products were Nd₂(CrO₄)₃ and NdCrO₃, and from 880 to 950°C the sole product was NdCrO₃. The variation with temperature of the amounts of products formed at constant reaction time was investigated. The kinetics of the reaction were investigated at the following temperatures, 630, 650, 680, 700, 720 and 760°C. At each temperature, with increasing time the amount of Nd₂(CrO₄)₃ formed increased to a maximum and then decreased whereas the amount of NdCrO₃ formed increased continually. The results together with experiments on the effect of oxygen and argon atmospheres are interpreted as follows. NdCrO₃ is not formed by direct combination of Nd₂O₃ with Cr₂O₃. Instead the reaction of the two oxides produces Nd₂(CrO₄)₃, the thermal decomposition of which then leads to the formation of NdCrO₃. The absence of NdCrO₄ as a reaction product is investigated and discussed as is the absence of NdCrO₃ as a reaction product below 630°C.     

Rapid spectrophotometric determination of chromium(III)

A spectrophotometric procedure is suggested for the determination of Cr(III). The reaction between Cr(III) and 2-(5-bromo-2-pyridylazo)-5-dimethylaminophenol is accelerated by sodium dodecyl sulphate(SDS), sodium benzoate causes a further increase in the absorbance of the chelate. The optimum pH range for the reaction is 5-5.8(benzoate buffer). The chelate exhibits maximum absorbance at 590 nm, obeys Beer's law over the concentration range 0.02-0.56 microg/ml of Cr(III), has molar absorptivity of 7.8 x 10(4) 1. mol(-1) cm(-1) and a Sandell sensitivity of 0.66 ng/cm. The metal to ligand ratio is 1:2 in the absence of SDS and 1:1 in its presence. A procedure for the determination of Cr(III) and Cr(VI), when present together, is described. The method has been applied to the analysis of Cr(III) in tap water.     

Synthesis and spectral characterization of novel oxo-bridged, thiocarboxylato complexes of chromium(III)

A variety of novel oxo-bridged trinuclear mixed-ligand complexes of chromium(III) were synthesized by substitution reactions of acetate ions from their respective acetate complexes. The isolated products of the types [Cr₃O(OAc)₃(OOCR] ₃ ⁺ and [Cr₃O(SOCPh)₃(OOCR)₃]⁺ (R = C₁₃H₂₇, C₁₅H₃₁ or C₁₇H₃₅) are mixed-ligand chromium(III) complexes with straight-chain carboxylic and thiocarboxylic acids. These were characterized by elemental analyses, spectral (infrared, electronic, FAB mass, and powder XRD) studies, molar conductances, and magnetic susceptibility measurements. The IR spectra suggested the bridging nature of the carboxylate and thiocarboxylate anions along with v _as (Cr₃O) vibrations in the complexes. The trinuclear nature of the complexes was assessed from the FAB mass data. Electronic absorption spectra and magnetic moment data were in favor of an octahedral environment around chromium(III), which was supported by their powder X-ray diffraction data. Conductance measurements indicated that the complexes were 1: 1 electrolytes in nitrobenzene. Structures of the complexes were established on the basis of spectral and other physicochemical studies. The text was submitted by the authors in English.