X-Ray Diffraction Analysis of Aluminum Hexamolybdenocobaltate(III) and Hexamolybdenocromate(III)

Isostructural crystals of aluminum hexamolybdenocobaltate(III) and hexamolybdenocromate(III) Al[MMo₆O₁₈(OH)₆] · 16H₂O (M = Co(III) and Cr(III)) were studied using X-ray diffraction analysis. These compounds crystallize in the triclinic system: space group P , Z = 1, (calcd) = 2.665 and 2.611 g/cm³, respectively. The unit cell parameters were determined: for aluminum hexamolybdenocobaltate(III), a = 6.796(1) Å, b= 11.248(2) Å, c = 11.568(2) Å; = 101.36(2)°, = 96.95(2)°, = 102.23(2)°; for aluminum hexamolybdenocromate(III), a = 6.838(1) Å, b = 11.312(2) Å, c = 11.605(2) Å; = 101.29(3)°, = 97.13(3)°, = 102.15(3)°.     

Cerium(III) Pivalate [Ce(Piv)3(HPiv)3]2: Synthesis, Crystal Structure, and Thermal Stability

The [Ce(Piv)₃(HPiv)₃]₂ complex was synthesized by reacting cerium(III) nitrate with NH₄(Piv) (1 : 4) (HPiv is pivalic acid) in an aqueous solution and by further recrystallization of the obtained precipitate from a 5% HPiv solution in n-hexane. The complex structure and unit cell parameters were determined by X-ray diffraction analysis: a = 16.586(8) Å, b = 12.313(5) Å, c = 20.765(10) Å, = 109.27(2)°, V = 4003(2) ų, Z = 4, R = 0.0546, R _w = 0.0836, space group P2₁/n. The crystal structure of [Ce(Piv)₃(HPiv)₃]₂ consists of centrosymmetric dimeric molecules with the Ce(III) atoms bound by four bridging pivalate ligands. Heating in an atmosphere of nitrogen is accompanied by the elimination of six HPiv molecules in the range of 90–190°C; the thermolysis of the obtained Ce(Piv)₃ occurs at 290–450°C. In addition to the thermal decomposition, the sublimation of Ce(Piv)₃ was also observed under reduced pressure (0.01 mmHg) in the temperature interval of 290–350°C.     

The thermolysis of zinc bis(citrato)ferrate(III) dodecahydrate

The thermolysis of zinc bis(citrato)ferrate(III)dodehydrate has been investigated from ambient temperature to 600 °C using various physico-chemical techniques, i.e., simultaneous TG-DTG-DTA, XRD, Mössbauer and I.R. spectroscopy. After dehydration at 200 °C, the anhydrous complex undergoes oxidative decomposition to yield -Fe₂O₃ and ZnO at 350 °C. Subsequently, the cations remix to yield fine particles of zinc ferrite, ZnFe₂O₄ as a result of solid state reaction between -Fe₂O₃ and ZnO at a temperature (450 °C) much lower than for ceramic method.     

Crystal Structure of Ammonium Undecafluorotriantimonate(III) (NH4)2Sb3F11

The crystal structure of a novel antimony(III) fluoride complex, ammonium undecafluorotriantimonate(III) (NH₄)₂Sb₃F₁₁, was determined. The crystals are triclinic: a = 7.780(2) Å, b = 8.370(2) Å, c = 10.620(1) Å, = 71.06(1)°, = 89.03(1)°, = 63.58(1)°, V = 579.1(2) ų, Z = 2, (calcd) = 3.500 g/cm³, (exp) = 3.51 g/cm³, F(000) = 548.0, space group P . The structure consists of anionic [Sb₃F₁₁]^2– chains and ammonium cations combined into a framework by the N–H···F hydrogen bonds.     

Antimony(III) Chloride Complexes with Benzylpyridines: Synthesis and Luminescence. Crystal Structure of Bis(2-benzylpyridinium) Pentachloroantimonate(III)

The antimony(III) chloride complexes with 2- and 4-benzylpyridine were synthesized and studied using elemental analysis, X-ray diffraction analysis, IR spectroscopy, and luminescence spectroscopy. The crystal structure of bis(2-benzylpyridinium) pentachloroantimonate(III) was determined. The crystals are triclinic: a = 9.628(1) Å, b = 15.284(2) Å, c = 19.174(2) Å, = 99.962(2)°, = 101.233(2)°, = 99. 216(2)°; Z = 4, (calcd) = 1.591 g/cm³, space group P , R = 0.0358. The structure consists of polymeric chains of [Sb₂Cl₁₀]^4n– _n anions and [C₁₂H₁₁NH]⁺ cations combined into a framework by the N–H···Cl hydrogen bonds. The electronic and geometrical factors responsible for a relatively low intensity of the luminescence emitted by the complexes of antimony(III) chloride with 2- and 4-benzylpyridine at 77 K are discussed.     

Spectrofluorimetric flow-injection determination of cerium in carbon and low alloy steels

Cerium can be determined spectrofluorimetrically (_em 350 nm, _ex 260 nm) based on the relatively intense native fluorescence of the cerium(III) aquo-ion. The main potential interference in the analysis of steel from iron(III), cerium(IV) and chromium(VI) are removed by use of a carrier solution containing 2.5% w/v hydroxylammonium chloride. The slight residual interference from iron(II) can be corrected by a matrix matching factor linearly related to the amount of iron present. The calibration graphs are linear over the range 0–7 g ml^–1 based on 250 l injection volumes. The sampling rate was 30 h^–1. The relative standard deviation was 2.0% (n=5) at 3 g ml^–1 cerium. The system has been applied to the determination of cerium in carbon or low alloy steels.     

Polymethylenebis(octylarsinic acids), [C8H17As(O)OH]2 (CH2)n,as reagents for the liquid-liquid extraction of cerium(III) and Europium(III)

Summary Cerium(III) and europium(III) are extracted at 50° C by [C₈H₁₇ As(O)OH]₂(CH₂) _n (n=6, 8, 12) inn-octanol from aqueous solutions containing NaCl and acetic acid/sodium acetate in the pH range 6.7–8.0. The extraction coefficient, , reached a maximum of: 10.0, 13.2 forn=6; 10.7, 20.0 forn=8; 4.68, 6.03 forn=12; at an aqueous equilibrium pH of: 7.65, 7.80 forn=6; 7.89, 7.95 forn=8; 7.81, 7.82 forn=12; corresponding to the extraction efficiency of: 91%, 93% forn=6; 92%, 95% forn=8; 80%, 83% forn=12; for cerium and europium, respectively.The log was found to be second power dependent for cerium and one and one-half power dependent for europium on the negative log of the aqueous equilibrium [H⁺] forn=6, 8, 12. The extractions were done at 50°C using organic reagent solutions (1.09×10^–3 M forn=12, 1.08 × 10^–3 M forn=8, 1.32×10^–3 M forn=6) and aqueous solutions of 1.0×10^–5 M for CeCl₃ and EuCl₃, having their Cl^– ionic strengths adjusted to 0.100 molar with NaCl. It was found that the slopes increase in the pH dependence studies in the seriesn=6, 8, and 12 for both cerium and europium metal ions. The reagent dependence studies were done at 50°C and pH: 7.00, 6.80 forn=6; 7.30, 7.20 forn=8; 7.45, 7.35 forn=12; for cerium and europium, respectively. The log was found to be first power dependent on the log of the uncomplexed reagent concentration at equilibrium. It is assumed that the complexes are hexacoordinated.

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Polymethylenebis-Oktylarsinsäuren als Reagenzien für die Flüssig-flüssig-Extraktion von Cer(III) und Europium(III)

Zusammenfassung Cer(III) und Europium(III) werden aus wäßrigen, Kochsalz und Essigsäure/Acetat enthaltenden Lösungen bei 50°C mit C₈H₁₇As(O)OH₂(CH₂)_n (_n=6, 8, 12) im pH-Gebiet 6,7–8,0 extrahiert. Der Extraktionskoeffizient erreicht ein Maximum von: 10,0, 13,2 für_n=6; 10,7, 20,0 fürn=8; 4,68, 6,03 fürn=12; bei einem wäßrigen Gleichgewicht-pH von: 7,65, 7,80 fürn=6; 7,89, 7,95 fürn=8; 7,81, 7,82 fürn=12, entsprechend dem Aus maß der Extraktion von: 91%, 93% fürn=6; 92%, 95% fürn=8; 80%, 83% fürn=12; für Ce bzw. Eu.Für Cer ist der log in zweiter Potenz, für Europium in erster und 1/2 Potenz abhängig vom negativen log des wäßrigen [H⁺]-Gleichgewichtes fürn=6, 8, 12. Die Extraktionen wurden bei 50°C mit organischen Reagens-lösungen (1,09×10^–3 M fürn=12, 1,08×10^–3 M fürn=8, 1,32×10^–3 M fürn=6) und mit wäßrigen Lösungen von 1,0×10^–5 M für CeCl₃ und EuCl₃ durchgeführt, deren lonenstärke für Cl^– mit NaCl auf 0,100M eingestellt wurde. Bei der Untersuchung der pH-Abhängigkeit bei den Reihenn=6, 8 und 12 ergab sich ein Anstieg sowohl für Ce wie für Eu. Die Reagens-Abhängigkeit wurde bei 50°C und bei pH 7,00, 6,80 fürn=6; 7,30, 7,20 fürn=8; 7,45, 7,35 fürn=12 für Cer bzw. Europium geprüft. Der log war einfach abhängig vom log der Konzentration des unkomplexierten Reagens beim Gleichgewicht. Es wird angenommen, daß die Komplexe hexakoordiniert sind.

     

Electrical properties of poly(bis(β-phenoxyethoxy)phosphazene) and its complexes

Electrical and dielectrical properties of poly(bis(-phenoxyethoxy)phosphazene) (I) and its complexes with various content ratios of AgSO₃CF₃ to monomeric unit (0.25/1 (II) and 0.5/1 (III) in molar ratio) were investigated.Dc conductivity of respective samples at 18 °C were 6.1×10^–12, 4.4×10^–9, and 7.1×10^–8 S/m.Dc conduction was considered to be due to ion hopping. Charge mobility ranged from 3×10^–12 to 6× 10^–11 m²/Vs depending on the applied field in sample II. In sample I, a tan peak was found which can be ascribed to molecular relaxation of main chains. The peak vanished upon introducing AgSO₃ CF₃. Temperature dependence of total conductivity ( _T ) measured byac method in the temperature range between –150 °C and 50 °C showed several peaks at the temperatures corresponding to the peak temperatures of tan. Total conductivities of respective samples at 100 kHz were 4.9×10^–7 (69 °C), 1.7×10^–4 (45 °C), and 1.5×10^–4(40°C)S/m.     

Chloride and iodide mediated oxidation of antimony(III) by cerium(IV) in aqueous sulphuric acid medium

The micro amounts of iodide (10⁻⁷) (mol dm⁻³) and chloride (10⁻²) (mol dm⁻³) mediated oxidation of antimony(III) by cerium(IV) in an aqueous sulphuric acid medium have been studied spectrophotometrically at 25 °C and μ = 3.10 mol dm⁻³. The stoichiometry is 1:2 in chloride and iodide mediated reactions. i.e. one mole of antimony(III) requires two moles of cerium(IV). In the case of chloride mediated reaction, the reaction was first order in cerium(IV) and halide concentrations, whereas in the case of iodide mediated reaction the order with respect to [cerium(IV)] was unity and with respect to iodide concentrations was more than unity (ca. 1.4). In both chloride and iodide mediated reactions the order with respect to antimony(III) concentrations was less than unity. Increase in sulphuric acid concentration increased the rate. The order with respect to H⁺ ion concentration was less than unity. Added products, cerium(III) and antimony(V) did not have any significant effect on the reaction rate. The active species of oxidant was understood to be , whereas that of reductant as SbCl₃ in the case of chloride and SbI²⁺ in case of iodide mediated reactions. The possible reaction mechanisms were proposed and the activation parameters were determined and discussed.     

Stability constants of iron(III) borate complexes

The ultraviolet absorbance data from experiments conducted at constant pH and total iron concentration but variable B(OH)₃ concentration were used to determined the stability constants of FeB(OH) ₄ ²⁺ and Fe[B(OH)_{4 2} ⁺ at 25°C and an ionic strength of 0.68. The estimates obtained were *₁ = 1.0 ± 0.2 × 10^–2 and *₂ = 2 ± 1 × 10^–5, respectively (uncertainties are two times the standard error of the estimates). A calculation of the extent of iron(III) borate formation in ocean water at pH 8.2 shows that iron(III) borates are not a significantly large component of iron(III) speciation in seawater.     

Highly-sensitive simultaneous detection of lanthanide(III) ions as kinetically stable aromatic polyaminocarboxylato complexes via capillary electrophoresis using resolution enhancement with carbonate ion

An aromatic polyaminocarboxylate ligand, 1-(4-aminobenzyl)ethylenediamine-N,N,N,N-tetraacetate (ABEDTA), is proposed as a complexing reagent in the pre-capillary mode so as to form kinetically inert Ln(III) complexes, meaning that no added ligand is necessary in alkaline carrier buffer solutions. In addition, highly-sensitive detection is possible through a light-absorbing moiety of an aminobenzyl group in the ligand. The fine-tuning of the electrophoretic mobilities of the Ln-abedta complexes is successfully achieved by adding an auxiliary carbonate ion ligand which alters the charge-to-size ratio of the complexes through fast exchange equilibria in a carrier buffer. In fact, all of the complexes are detectable with very similar analytical sensitivity and acceptable resolution (except for Ln=Sm, Eu, Gd) by using NaOH-borate carrier buffer solution at pH 12.35 with 20 mM of Na₂CO₃. A typical detection limit for Tb(III) ion (to 3) is as low as 0.94 M, which translates to an absolute amount of 9.4 fmol in a 1.0×10^–8 dm^-3 (10 nL) injection.     

On the mechanism of racemisation of dichlorobis(ethylenediamine)-metal chlorides [metal = cobalt(III) or chromium(III)] in the solid state

Summary In the solid state l-cis-[M(en)₂Cl₂]Cl [M=cobalt(III) or chromium(III)] undergoes thermal racemisation smoothly at 158 °C without anycis-trans interconversion. The values of k_rac, H and S are 6 × 10^–6s^–1, 218 kJM^–1 and 156.1 JK^–1M^–1 for the cobalt(III) complex and 3.5 × 10^–5s^–1, 229.7 kJM^–1 and 197.9 JK^–1M^–1 for the chromium(III) complex, respectively. The results are only in accord with a rhombic twist mechanism of the type originally proposed by Ray and Dutt for [M(AA)₃] complexes.     

Hexa(isothiocyanato)chromate(III) Hydro-Bis(Pyridine N-Oxide) Complex: Synthesis and Crystal Structure

A new complex of hexa(isothicyanato)chromate(III) hydro-bis(pyridine N-oxide) [(Py)₂H]₃[Cr(NCS)₆] was synthesized and studied by X-ray diffraction analysis. The coordination polyhedra of Cr atoms are the perfect octahedra that form the layered structure. Molecules of pyridine N-oxide form bimolecular cationic associates that compensate the charge on the complex anions. The crystals are triclinic: a = 11.559(2) Å; b = 12.644(3) Å; c = 16,110(4) Å; = 90.02(2)°; = 95.15(2)°; = 98.23(2)°; V = 2320.6(9) ų; _calcd = 1.394 g/cm³. Z = 2, space group P1¯.     

Decomposition kinetics ofbis(biguanide)silver(III) cation in acid perchlorate media

Summary In acid perchlorate media, the title complex undergoes intramolecular redox decomposition generating ultimately Ag⁺ ion and oxidation products of the ligand. The reaction follows a simple first-order process, and the observed pseudo-first-order rate constant is given by k_obs=k₀+kK_a/[H⁺] where K_a is the deprotonation constant of the parent complex; pK_a is approximately 5.9 at 30°. The values of 10⁵ k₀(s^–1) and 10⁷ kK_a (Ms^–1) at 30°, I=1.0 M, are 9.3±0.1 and 11.8±1.3; corresponding H (kJ/mol), S (JK^–1 M^–1) values are 105±0.5, 23±1 and 79±8,-96±5, respectively. The results are compared with those for similar reaction of (ethylenebisbiguanide)silver(III) and effect of change in ligand structure on kinetic behaviours of these complexes is discussed.     

Synthesis and characterization of uranium (IV) phosphate-hydrogenphosphate hydrate and cerium (IV) phosphate-hydrogenphosphate hydrate

A new uranium (IV) phosphate of proposed formula U₂(PO₄)₂HPO₄·H₂O, i.e. uranium phosphate-hydrogenphosphate hydrate (UPHPH), was synthesized in autoclave and/or in polytetrafluoroethylene closed containers at 150 °C by three ways: from uranium (IV) hydrochloric solution and phosphoric acid, from uranium dioxide and phosphoric acid and by transformation of the uranium hydrogenphosphate hydrate U(HPO₄)₂·nH₂O. The new product appears similar to the previously published thorium phosphate-hydrogenphosphate hydrate Th₂(PO₄)₂HPO₄·H₂O (TPHPH). From preliminary studies, it was found that UPHPH crystallizes in monoclinic system (, , , β=91.67(3)° and ). Heated under inert atmosphere, this compound is decomposed above 400 °C into uranium phosphate-triphosphate U₂(PO₄)P₃O₁₀, uranium diphosphate α-UP₂O₇ and diuranium oxide phosphate U₂O(PO₄)₂.Crystallized cerium (IV) phosphate-hydrogenphosphate hydrate Ce₂(PO₄)₂HPO₄·H₂O (CePHPH) was also synthesized from (NH₄)₂Ce(NO₃)₆ and phosphoric acid solutions by the same method (monoclinic system: , , , β=91.98(1)° and ). When heating above 600 °C, cerium (IV) is reduced into Ce (III) and forms a mixture of CePO₄ (monazite structure) and CeP₃O₉.     

Formation Thermodynamics of Binary and Ternary Lanthanide(III) Complexes with 1,10-Phenanthroline and Chloride in N,N-Dimethylformamide

Formation thermodynamics of binary and ternary lanthanide(III) (Ln = La, Ce, Nd, Eu, Gd, Dy, Tm, Lu) complexes with 1,10-phenanthroline (phen) and the chloride ion have been studied by titration calorimetry and spectrophotometry in N,N-dimethyl-formamide (DMF) containing 0.2 mol-dm^–3 (C₂H₅)₄NClO₄ as a constant ionic medium at 25°C. In the binary system with 1,10-phenanthroline, the Ln(phen)³⁺ complex is formed for all the lanthanide(III) ions examined. The reaction enthalpy and entropy values for the formation of Ln(phen)³⁺ decrease in the order La > Ce > Nd, then increase in the order Nd < Eu < Gd < Dy, and again decrease in the order Dy > Tm > Lu. The variation is explained in terms of the coordination structure of Ln(phen)³⁺ that changes from eight to seven coordination with decreasing ionic radius of the metal ion. In the ternary Ln³⁺-Cl^–-phen system, the formation of LnCl(phen)²⁺, LnCl₂(phen)⁺, and LnCl₃(phen) was established for cerium(III), neodymium(III), and thulium(III), and their formation constants, enthalpies, and entropies were obtained. The enthalpy and entropy values are also discussed from the structural point of view.     

The crystal and molecular structure oftrans-Di(methylsulphito)bis-(triphenylphosphine)platinum(II)

Summary The crystal and molecular structure oftrans-di(methylsulphito)bis(triphenylphosphine)platinum(II), Pt(SO₃Me)₂ (PPh₃)₂, derived from the reaction of Pt(PPh₃)₂ (O₂) with SO₂ in MeOH and in the presence of sodium tetraphenylborate(III), has been determined from diffractometer data. The complex crystallizes in the space group P ¯1- (C_i ¹) with one molecule in a unit cell of dimensionsa = 9.744(2) Å,b = 10.062(3) Å,c = 11.153(2) Å; = 68.59(2)°, = 82.69(2)° and = 62.25(2)°. Leastsquares refinement has led to a value of the conventional R index (on F) of 0.031 for the 3308 reflections having F²>3(F₀ ²). The complex is a typical square-planar platinum(II) complex with the platinum atom lying on a crystallographically imposed centre of symmetry. The important structural parameters are Pt-P 2.369(1) Å, Pt-S 2.308(1) Å, and the oxygen atoms complete an approximate tetrahedron about the sulphur atoms with S-O 1.448(5) Å and S-O(Me) 1.620(5) Å.     

Hydrogen peroxide oxidation of di(hydroxo)platinum(II) species in carboxylic acids

A facile procedure for synthesizing the mono(hydroxo)tris(carboxylato)platinum(IV) species has been achieved. The reaction of [Pt^II(OH)₂(dmpda)] (dmpda=2,2-dimethyl-1,3-propanediamine) with a 30% aqueous solution of H₂O₂ in the presence of a carboxylic acid produces a stable [Pt^IV(OOCR)₃(OH)(dmpda)] (R=Me, Et) complex in high yield. The crystal structures of [Pt^IV(OOCMe)₃(OH)(dmpda)] . H₂O (triclinic P1 bar, a=8.761(2) Å, b=9.245(3) Å, c=10.659(2) Å, =106.25(2)°, =93.90(2)°, =98.92(2)°, V=813.1(3) ų, Z=2, R= 0.0474) and [Pt^IV(OOCEt)₃(OH)(dmpda)] (monoclinic P2₁/c, a=12.777(4) Å, b=10.514(2) Å, c=14.971(3) Å, =107.40(2)°, V=1919.2(8) ų, Z=4, R=0.0611) show that the hydroxyl group has been selectively positioned at an axial site. The intramolecular hydrogen bond between the OH and C=O moiety exists (O(H)...=C, 2.83 Å for [Pt^IV(OOCMe)₃(OH)(dmpda)] · H₂O; 2.72 Å for [Pt^IV(OOCEt)₃(OH)(dmpda)]. Formation of the axial-mono(hydroxo)tris(carboxylato)platinum(IV) species may be ascribed to a combination of `reactive-equatorial effects' with `cis-addition' in the carboxylic acid.     

Kinetics and mechanism of base hydrolysis oftrans-bis(Hmalonato)bis(ethylenediamine)cobalt(III) ion

Summary The kinetics of the first step of base hydrolysis oftrans-bis(Hmalonato)bis(ethylenediamine)cobalt(III) [malH^–=HO₂CCH₂CO ₂ ^– ] has been investigated in the 15–35° C range, I=0.3 mol dm^–3 (NaClO₄) and [OH^–]=0.015–0.29 mol dm^–3. The rate law is given by –d In[complex]_T/dt=k₁[OH^–] and at 30° C, k₁=8.5×10^–3 dm³ mol^–1s^–1, H=117.0±7.0 kJ mol^–1 and S=99.0±24.0 JK^–1mol^–1. The activation parameters data are consistent with the SN₁ cb mechanism.