Ion pair association of complexes of La3+ and Nd3+ with Br− and NO3− in N,N-dimethylacetamide

The formation constants and the respective variations of enthalpy were obtained by means of calorimetric titration of the lanthanides La³⁺ and Nd³⁺ with bromide and nitrate in N,N-dimethylacetamide. These thermochemical data were calculated for the 1:1 and 1:2 species which are less stable than the corresponding species obtained with chloride. The order of stability Cl^? > Br^?>NO₃^? was established for both species of La³⁺, and the order Br^?>Cl^?>LNO₃^? for 1:1 species of Nd³⁺. NdCl₂⁺ and NdBr₂⁺ species were not detected. Our results support the view that the metal-anion interactions involve inner sphere species.     

Effect of oxide additives on radiolytic decomposition of potassium nitrate

Gamma-ray induced decomposition of binary mixtures of potassium nitrate with 90, 70, 50, 30 and 10 mol% SiO₂, Al₂O₃, MnO₂, V₂O₅, La₂O₃, CeO₂, Sm₂O₃, Eu₂O₃, Gd₂O₃ and Dy₂O₃ has been studied at different doses up to 500 kGy. Radiolytic decomposition of the nitrate is affected by the concentration of the oxide in the binary mixture as well as by the absorbed dose. The enhancement is up to 10³ times at 90 mol% of the additive.G(NO₂ ⁻) values calculated on the basis of electron fraction of the nitrate decrease with the increasing concentration of the nitrate. A comparison ofG(NO₂ ⁻) for 90 mol% oxides shows decreasing trend as Gd₂O₃>Sm₂O₃≈Dy₂O₃> Eu₂O₃>CeO₂>Al₂O₃>V₂O₅>SiO₂>MnO₂. ESR and TL measurements suggest the formation of radical species which interact with the radical species of nitrate causing enhanced decomposition by energy transfer mechanism.     

Non equivalency of oxygen nuclei in 17O−2 adsorbed on oxides

Oxygen enriched with ¹⁷O has been used to investigate the nature of oxygen species adsorbed on oxides. The variations in the hyperfine constants of O^?₂, small (<3%) for MgO and ZnO, are due to different adsorption sites. They become large (>15%) for supported molybdenum due to the different spin densities on the two nuclei showing that O^?₂ probably adsorbed at an angle to the surface.     

Synthesis and characterization of zirconium(IV) 4-amino, 3-hydroxy naphthalene sulfonate ion exchanger: Quantitative separation of mercury from numerous metal ions

Zirconium (IV) 4-amino, 3-hydroxy naphthalene sulfonate ion-exchanger has been synthesized by mixing equimolar solutions of zirconium oxychloride and ammonium hydroxide in molar ratio 1:1.66 to get a gelatinous material. To this were added varying amounts of 4-amino, 3-hydroxynaphthalene sulphonic acid (ANSA) with constant stiring in order to ensure a complete adsorption of organic molecules to the surface of the gel. The ion exchange material shows a dual character possessing both cation and anion exchange capacities. The former is attributed to the dissociation of strong sulphonic groups from ANSA and acidic sites of hydrous oxide gel, the later one is due to the formation of a positive charge on the nitrogen atom ; in addition, the material may have a sorption capacity. A preliminary investigation to characterize the material has been carried out which includes IR, TGA, DTA and X-ray diffraction. On the basis of distribution coefficients the separation of Hg⁺² from Zn²⁺, Al²⁺, Ni²⁺, Ce⁴⁺, Mg²⁺, Pb²⁺, Mn²⁺, Cu²⁺, has been achieved. The decreasing sequence of Kd values for different anionic species are found to be PO₄³⁻ > Fe (CN)₆³⁻ > MnO₄⁻ > VO₃⁻ > AsO₄³⁻ > C₂O₄²⁻ and for halides Cl⁻ > Br⁻ > I⁻.     

Removal of multiple pollutants from water using noble Ag/Au/magnetite/graphene/H2O2 system under light and ultrasound irradiation

Ag/Au/Fe₃O₄/graphene composites prepared by a hydrothermal method demonstrated excellent activation of H₂O₂ and were used to degrade methylene blue (MB) in solution in the presence of organic acids and inorganic ions under light and ultrasound irradiation. The physicochemical properties of the obtained composites were characterized using various methods. The results showed that the composites exhibited excellent magnetic properties, crystallinity, and stability. The results of catalysis experiments revealed that the removal efficiency of MB increased when Ag and Au were both incorporated into the Fe₃O₄/graphene/H₂O₂ system compared with the removal efficiency achieved with separate Ag-Fe₃O₄/graphene/H₂O₂ and Au-Fe₃O₄/graphene/H₂O₂ systems, indicating a substantial synergistic interaction between the two metallic nanoparticles and the Fe₃O₄/graphene/H₂O₂ systems. The presence of an organic acid accelerated degradation of the MB/H₂O₂ system, whereas almost all of the investigated anions inhibited the degradation of MB; their inhibition effects followed the order CO₃^2? > NO₃^? > Cl^? > F^? > H₂PO₄^? > SO₄^2? > I^?. Cations of Na⁺, K⁺, Ca²⁺, and Mg²⁺ also suppressed MB degradation, likely because of the influence of Cl^? coexisting in the solutions.     

Preparation and Ir, 31P,and 93Nb NMR spectroscopic investigation of phosphine derivatives of η5-C5H5Nb(CO)4

UV irradiation of η⁵-C₅H₅Nb(CO)₄ in the presence of the phosphine ligands L (L = 2 PEt₃, Ph₂P(CH₂)₂PPh₂ (p₂(n), n = 1–5), cis-Ph₂PCH=CHPPh₂ (c-dpe)), and the mixed arsine-phosphine ligands Ph₂AsCH₂CH₂PPh₂ (arphos) and o-C₆H₄(AsPh₂)(PPh₂) (pab) yields the well defined complexes cis-[η⁵-C₅H₅Nb(CO)₂L]. The monosubstituted species η⁵-C₅H₅Nb(CO)₃L have been characterized spectroscopically. P₂Ph₄ forms mono- and dinuclear, mono- and biligate carbonylniobium complexes.Shielding of the ⁹³Nb nucleus increases in the sequences (i) Ph₂As- < Ph₂P-, (ii) chelate 4-ring < chelate 5-ring and (iii) η⁵-C₅H₅Nb(CO)₂L < η⁵-C₅H₅Nb(CO)₃L < η⁵-C₅H₅Nb(CO)₄, and ³¹P coordination shifts decrease in the order c-dpe > pab > arphos > p₂(2) > p₂(5) > p₂(4) ～ PEt₃ > p₂(3) > p₂(1). The trends generally parallel those for the corresponding NMR parameters of the vanadium complexes. Paramagnetic contributions to the overall shielding are smaller for the ⁹³Nb than for the ⁵¹V nucleus, and this is explained in terms of increased covalency and decreased π-interaction in the niobium complexes.     

Complexing tendencies of UO 22+ and Th4+ in their mixed ligand complexes with aminopolycarboxylates and resorcinol or its derivatives

Formation contants (log K _MAL ^MA ) of mixed ligand complexes MAL, where M = UO ₂ ²⁺ or Th⁴⁺, A = IMDA, NTA, HEDTA, EDTA, CDTA or DTPA, and L = resorcinol (res), 2-methyl resorcinol (2-Me-res), 5-methyl resorcinol (5-Me-res) or 4-chloro resorcinol (4-Cl-res), have been determined pH-metrically by the Irving-Rossotti approach at 25°C and at an ionic strength,I = 0.2(moldm⁻³KNO₃). The observed stability sequences are IMDA > NTA > HEDTA > EDTA > CDTA > DTPA, and 4-Cl-res > 5-Me-res > 2-Me-res > res with respect to primary and secondary ligands, respectively. Th⁴⁺ forms more stable mixed complexes than UO ₂ ²⁺ . The A ΔlogK values are negative due mainly to the charge repulsion involved in the complexation MA + L⇋MAL.     

An infrared study of molybdenum /V/ hydroxide

The IR spectra of paramagnetic Mo/V/ oxygen compounds that are claimed in the literature to be unstable, were measurement in the 4000–3000 and 1200–250 cm^?1 regions. The spectra are poor but show a few bands in the valence and in the OH groups vibrations regions. Mo/V/ hydroxide can be reversibly or irreversibly dehydroxylated thermally in vacuum. The irreversible dehydroxylation of amorphous species containing Mo/V/ hydroxide takes place at >350°C, and is connected with a rearrengement of the atomic OMoO linkage and with crystallization of MoO₃, MoO₂ and Mo₄O₁₁ phases.     

The structure and energy of SiH+5. comparisons with CH+5 and BH5

Differences between SiH⁺₅ and CH⁺₅ are more significant than the similarities. The proton affinity of SiH₄ exceeds than of CH₄ by ≈25 kcal/mol. but the heat of hydrogenation of SiH⁺₃ is smaller than that of CH⁺₃ by nearly the same amount. Like CH⁺₅ the C₅ structures of SiH⁺₅ are preferred, but SiH⁺₅ is best regarded as a weaker SiH⁺₃—H₂ complex. D_3h, C_2v, and C_4v forms are much higher in energy and SiH⁺₅ should not undergo hydrogen scrambling (pseudorotation) readily, as does CH⁺₅ The neutral BH₅ is only weakly bound toward loss H₂, and the D_3h. C_2v, and C_4v forms are also high in energy. The contral-atom electronegativities, C⁺ > B > Si⁺, control this behavior. The electronegativities also determine the ability to bear positive charges. Thermodynamically. SiH⁺₅ and SiH⁺₃ are more stable than CH⁺₅ and CH⁺₃, respectively; hydride transfer occurs from SiH₄ to CH⁺₃ and proton transfer from CH⁺₅ to SiH₄.     

CrOx/SiO2催化剂上丙烷在CO2气氛中脱氢反应的研究

采用XRD、UV-vis DRS、ESR和微分吸附量热等技术,考察了铬担载量分别为2.5、5和10wt%的CrO_x/SiO₂催化剂的结构、表面性质和氧化还原性能。结果表明,催化剂表面上存在多种Cr的氧化态和聚集形式。随着Cr担载量从2.5wt%到10wt%的逐渐增大,催化剂表面占主导地位的Cr物种由CrO₃单体转为多聚CrO₃和Cr₂O₃晶相。在CO₂气氛中催化剂对丙烷转化率和丙烯选择性的大小顺序为2.5wt%CrO_x/SiO₂>5wt%CrO_x/SiO₂>10wt%CrO_x/SiO₂,反应过程中的原位ESR和UV-visDRS测定结果表明,催化剂表面的反应活性中心为Cr⁵⁺,Cr⁵⁺可由催化剂预处理过程中Cr³⁺的氧化及丙烷反应过程中CrO₃单体的还原产生,在反应中CO₂可使Cr³⁺重新氧化为Cr⁵⁺.     

Formation and Stability of Binary Complexes of Divalent Ecotoxic Ions (Ni, Cu, Zn, Cd, Pb) with Biodegradable Aminopolycarboxylate Chelants (dl-2-(2-Carboxymethyl)Nitrilotriacetic Acid, GLDA, and 3-Hydroxy-2,2′-Iminodisuccinic Acid, HIDS) in Aqueous Solutions

The protonation and complex formation equilibria of two biodegradable aminopolycarboxylate chelants {dl-2-(2-carboxymethyl)nitrilotriacetic acid (GLDA) and 3-hydroxy-2,2??-iminodisuccinic acid (HIDS)} with Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ ions were investigated using the potentiometric method at a constant ionic strength of I?=?0.10?mol·dm^?3 (KCl) in aqueous solutions at 25?±?0.1?°C. The stability constants of the proton?Cchelant and metal?Cchelant species for each metal ion were determined, and the concentration distributions of various complex species in solution were evaluated for each ion. The stability constants (log₁₀ K _ML) of the complexes containing Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ ions followed the identical order of log₁₀ K _CuL?>?log₁₀ K _NiL?>?log₁₀ K _PbL?>?log₁₀ K _ZnL?>?log₁₀ K _CdL for either GLDA (13.03?>?12.74?>?11.60?>?11.52?>?10.31) or HIDS (12.63?>?11.30?>?10.21?>?9.76?>?7.58). In each case, the constants obtained for metal?CGLDA complexes were larger than the corresponding constants for metal?CHIDS complexes. The conditional stability constants (log₁₀ $ K_{\text{ML}}^{'} $ ) of the metal?Cchelant complexes containing GLDA and HIDS were calculated in terms of pH, and compared with the stability constants for EDTA and other biodegradable chelants.     

An ab initio molecular orbital study of the deprotonation of amines

The geometries of the amines NH₂X and amido anions NHX^?, where X = H, CH₃, NH₂, OH, F, C₂H, CHO, and CN have been optimized using ab initio molecular orbital calculations with a 4-31G basis set. The profiles to rotation about the N? X bonds in CH₃NH^?, NH₂NH^?, and HONH^? are very similar to those for the isoprotic and isoelectronic neutral compounds CH₃OH, NH₂OH, and HOOH. The amines with unsaturated bonds adjacent to the nitrogen atoms undergo considerable skeletal rearrangement on deprotonation such that most of the negative charge of the anion is on the substituent. The computed order of acidity for the amines NH₂X is X = CN > HCO > F ≈ C₂H > OH > NH₂ > CH₃ > H and for the reaction NHX^? + H⁺ → NH₂X the computed energies vary over the range 373–438 kcal/mol.     

Effect of anions on the dissolution of Al in acid solutions

The effect of Cl^?, Br^?, I^?, ClO₄^?, NO₃^?, HSO₄^?, HCrO₄^? and H₂PO₄^? on the of Al in 2 M HCl is studied by the thermometric method. Three sets of experiments are carried out, which allow the variation of the concentration of the various species in a programmed manner. Dissolution promotion is noted in solutions to which HCl, HBr and H₂CrO₄ are added. The way of action of each of these anions is discussed. Additions of HI, HClO₄, H₂SO₄ and H₃PO₄, on the other hand, first retard and later enhance the dissolution of Al in 2 M HCl, as their concentration in solution is increased. This is related to anion adsorption, which is counterbalanced by increase in acidity. HNO₃ differs from the other tested acids in causing only dissolution retardation. Experiments in which LaCl₃ is added to the test solution indicate that the NO₃^? is adsorbed as such on Al₂O₃. The ability of the various anions to retard the dissolution of Al in 2 M HCl decreases in the succession: NO₃^? (strong)>I^?>HSO₄^?>H₂PO₄^?>Br^?, ClO₄^? (weak)     

New Molybdenyl Iodates: Hydrothermal Preparation and Structures of Molecular K2MoO2(IO3)4 and Two-Dimensional β-KMoO3(IO3)

Two new molybdenyl iodates, K₂MoO₂(IO₃)₄ (1) and β-KMoO₃(IO₃) (2), have been prepared from the reactions of MoO₃ with KIO₄ and NH₄Cl at 180°C in aqueous media. The structure of 1 consists of molecular [MoO₂(IO₃)₄]²⁻ anions separated by K⁺ cations. The Mo(VI) centers are ligated by two cis-oxo ligands and four monodentate iodate anions. Both terminal and bridging oxygen atoms of the iodate anions form long ionic contacts with the K⁺ cations. β-KMoO₃(IO₃) (2) displays a two-dimensional layered structure constructed from ²_∞[(MoO₃(IO₃)]¹⁻ anionic sheets separated by K⁺ cations. These sheets are built from one-dimensional chains formed from corner-sharing MoO₆ octahedra that run along the b-axis that are linked together through bridging iodate groups. K⁺ cations separate the layers from one another and form long contacts with oxygen atoms from both the iodate anions and molybdenyl moieties. Crystallographic data: 1, monoclinic, space group C2/c, a=12.8973(9) Å, b=6.0587(4) Å, c=17.694(1) Å, β=102.451(1)°, Z=4, MoKα, λ=0.71073, R(F)=2.64% for 97 parameters with 1584 reflections with I>2σ(I); 2, monoclinic, space group P2₁/n, a=7.4999(6) Å, b=7.4737(6) Å, c=10.5269(8) Å, β=109.023(1)°, Z=4, MoKα, λ=0.71073, R(F)=2.73% for 83 parameters with 1334 reflections with I>2σ(I).     

The coordinative properties of the ligands Ph2ECH2EPh2 (E = P,As, Sb) in carbonylvanadium complexes,and the molecular structure of η5-C5H5V(CO)3As2Ph4

Photo-reaction between the ligands Ph₂ECH₂EPh₂ (E = P: dppm, E = As: dpam, E = Sb: dpsm), L, and the vanadium complexes η⁵-C₅H₅V(CO)₄ and [Et₄N][V(CO)₆] yields monosubstituted mononuclear (dpsm) and dinuclear, ligand-bridged complexes (dpam, dpsm). With dppm, the final products are disubstituted chelate complexes, but monosubstituted mono- and dinuclear species are formed as intermediates.The shielding of the ⁵¹V nucleus decreases in the series dpsm > dppm > dpam and {M(CO)_n} > {M(CO)_n?1} L > {M(CO)_n?1}₂μ-L > {M(CO)_n?2}dppm ({M(CO)_n}[V(CO)₆]^?, η⁵-C₅H₅V(CO)₄). The half-widths of the NMR signals are greater for dinuclear than for mononuclear complexes.The crystal and molecular structures of η⁵-C₅H₅V(CO)₃As₂Ph₄ have been determined. The compound crystallizes in the space group P2₁/c with a = 1347.8, b = 1020.0, c = 2085.2 pm and β = 82.3°. Due to steric crowding, the ⁵¹V shielding is low composed to that of {η⁵-C₅H₅V(CO)₃}₂μ-dpam.     

Mise en evidence de la presence de plusieurs reactifs dans le cuprate (2 C2H5MgBr + CuI)

The cuprate reagent (2 C₂H₅MgBr + CuI) is composed of at least three species R₁, R₂, R₃, which react differently, with 1-mesityl-3-phenyl-2-propenone. R₁ is in the precipitate, R₂ and R₃ in the supernatant liquor. After addition of I and acetylation R₁ leads to the E enolacetate with a fair stereoselectivity, R₂ leads to the Z isomer only while R₃ is not selective.The stability order is R₃ > R₂ > R₁, the reactivity order R₂ > R₁ > R₃.     

IR and XPS studies of the reactivity of CO with Ti-H species at the support on Rh/TiO2 catalysts

Incorporation of hydrogen in Rh/TiO₂ samples during high temperature reduction (H₂ at T > 573 K), has been studied by TPD-MS. ESR and NMR data suggest that hydride-like species associated to Ti³⁺ ions at the support are formed, i.e, (Ti-H)³⁺. Rh(3d) XPS peaks (at 311.2, 306.5 eV) remain unchanged after removal of such hydride-like species (by outgassing at 773 K), though it modifies the adsorption capacity for CO and H₂, monitored by i.r. and NMR, thus indicating a SMSI effect which is reversed by outgassing at 773 K the sample. By heating in CO at 373–473 K bands at 1590, 1470 and 1220 cm^-1 are developed only in the samples saturated with hydrogen, while CH₃OH is detected in the gas phase. Experiments using a pulse microreactor in conditions that allow formation of such (Ti-H)³⁺ species, lead to methanol as the only product of syngas reaction. A model is proposed to explain generation of oxygenated compounds on these catalysts, whieh assumes reaction of the hydride-like species at the TiO₂ support with CO molecules either directly interacting with the support or hounded to the rhodium at the metal-support interface.     

Cover: Journal of the Chinese Chemical Society 9/2020

In this figure, the authors have scrutinized eight novel monodentate (1-4) and bidentate (1^’-4^’) derivatives of 2,5-diX-cyclopentasilylene-2,4-dienes (X = NH₂, OH, PH₂, and SH), and their corresponding complexes with Rh atom (1_Rh-4_Rh and 1^’_Rh-4^’_Rh, respectively), at M06/6-311++G** level of theory. The overall orders of σ-donation ability of monodentate and bidentate ligands are 1>2>3>4 and 1^’>2^’>3^’>4^’, respectively. More details about this figure will be discussed by Prof. Mohamad Z. Kassaee and his co-worker on page 1544-1551 in this issue.

     

Infrared studies of the diatomic molecules O2, N2, NO and H2 adsorbed on Fe2O3

An infrared spectroscopic study of the diatomic molecules O₂, N₂, NO and H₂ adsorbed under different conditions on Fe₂O₃ has been performed.Complex patterns of absorption on both α-Fe₂O₃ and γ-Fe₂O₃ activated in O₂ at high temperature are assigned to vibrations of two different chemisorbed O₂ species.N₂ molecules do not interact with “oxygen rich” α-Fe₂O₃ surfaces, but give N₂O^? and N₂O₂^2? species when chemisorbed on evacuated surfaces.NO molecules give complex patterns of absorption, depending on the gas pressure. Three different types of nitrate structures can be identified, as well as NO, NO^? and cis-N₂O₂ chemisorbed species. Chemisorbed water molecules are formed by contact of H₂ with Fe₂O₃ surfaces even at room temperature.     

Transition metal nitrosyls as nitrosylation agents : II.Photo-nitrosylation of η5-C5H5V(CO)3L(L = CO,Pz3) by [Co(NO)2Br]2

η⁵-C₅H₅V(NO)₂CO is prepared in 40% yield by the photo-reaction between η⁵-C₅H₅V(CO)₄ and [Co(NO)₂Br]₂.η⁵-C₅H₅V(NO)₂CO reacts by an S_N1 mechanism with various phosphines PZ₃ to yield η⁵-C₅-H₅V(NO)₂PZ₃. The phosphine complexes are also obtained by photo-induced ligand interchange between η⁵-C₅H₅V(CO)₃PZ₃ and [Co(NO)₂Br]₂, or η⁵-C₅H₅V(CO)₄ and Co(NO)₂Br(PZ₃). In all cases, the main cobalt species formed is Co(NO)(CO)₃. While the one-bond vanadiumphosphorus coupling constants of most of the phosphine complexes are virtually the same (ca 410 Hz),the chemical shift values δ(⁵¹V) (?1328 to ?973 ppm rel. VOCl₃) decrease in the order PF₃ > CO > P(OR)₃ > P(alkyl)₃ > PPh₃ > PPh(NEt₂)₂, reflecting the decreasing π-acceptor ability of the ligands. δ(⁵¹V) also decreases in the series of alkylphosphines PR₃ (R = Me, Et, Prⁿ, Buⁱ, Prⁱ, BU^t) as the cone angle of PR₃increases.