TiO2和Mg-Fe型类水滑石特征电离/络合平衡常数研究

The intrinsic surface reaction constants, pKa1^int, pKa2^int, p^＊KC^int and p^＊KA^int , were evaluated by a modifieddouble extrapolation （MDE） for TiO2 without structural charge and Mg-Fe hydrotalcite-like compounds （HTlc） with structural charge, respectively. The results of intrinsic surface reaction constants for TiO2 were compared with those obtained by class double extrapolation （CDE） in literature. Furthermore, the values of intrinsic surface reaction constants obtained by MDE were used to simulate the charging behaviors of the materials. The following conclusions were obtained. For TiO2 without structural charge, the pKa1^int and pKa2^int evaluated by MDE are equal to those by CDE, however the p^＊KC^int and p^＊KA^int evaluated by MDE are much different from those by CDE. In principle, the results of the p^＊KC^int and p^＊KA^int evaluated by MDE are more accurate than those by CDE. The values of intrinsic surface reaction constants obtained by MDE can excellently simulate the charging curves for TiO2 with the triple layer model （TLM）. For HTlc with positive structural charge, the results of ^＊KC^int=0 and ^＊KA^int →∞ were obtained by MDE, which means the inert electrolyte chemical binding does not exist; the point of zero net charge （PZNC） of c-independence also exist as the same as solid without structural charge, and the PHPZNC obtained by the acid-base titration can excellently be simulated and the surface charging tendency can be simulated to a great extent using the pKa1^int and pKa2^int evaluated by MDE and the diffuse layer model （DLM）.     

Yields of O2(1Σg+) and O2(1Δg) in the H + O2 reaction system,and the quenching of O2(1Σg+) by atomic hydrogen

The generation of metastable O₂(¹Σg⁺) and O₂(¹Δg) in the H + O₂ system of reactions was studied by the flow discharge chemiluminescence detection method. In addition to the O₂(¹Σg⁺) and O₂(¹Δg) emissions, strong OH(v = 2) → OH(v = 0), OH(v = 3) → OH(v = 1), HO₂(²A′₀₀₀) → HO₂(²A″₀₀₀), HO₂(²A′₀₀₁) → HO₂(²A″₀₀₀), and H O₂(²A″₂₀₀) → HO₂(²A″₀₀₀) emissions were detected in the H + O₂ system. The rate constants for the quenching of O₂(¹Σg⁺) by H and H₂ were determined to be (5.1 ± 1.4) × 10^?13 and (7.1 ± 0.1) × 10^?13 cm³ s^?1, respectively. An upper limit for the branching ratio to produce O₂(¹Σg⁺) by the H + HO₂ reaction was calculated to be 2.1%. The contributions from other reactions producing singlet oxygen were investigated.     

Analysis of autoionizing Rydberg series Cu I 3d 9 4snl with the multichannel quantum defect theory

Using atomic beam technique, a combination of collisional and laser excitation, and photoion detection, autoionizing Cu I states in the region of the ionization limits Cu II 3d ⁹ 4s(^3,1 D) were investigated. In spite of the complicated structure of the signals due to the four different ionization limits³ D ₃,³ D ₂,³ D ₁ and¹ D ₂ and the large number of possible (LSJ)-states, which can be reached by this experimental technique, the majority of the signals could be attributed to definite Rydberg series 3d ⁹ 4s(³ D ₃,³ D ₂,³ D ₁,¹ D ₂)nl (LSJ). Perturbations were analyzed by the three- and four-channel quantum defect theory and by Hartree-Fock calculations. General formulas for the calculation of the photoionization cross section by the four-channel quantum defect theory in the case of two closed and two open channels are given.     

Synthesis,structure, thermostability and luminescence properties of ZnII and CdII coordination polymers based on dimethysuccinate and flexible 1,4‐bis(imidazol‐1‐ylmethyl)benzene ligands

The design and synthesis of functional coordination polymers is motivated not only by their structural beauty but also by their potential applications. Zn^II and Cd^II coordination polymers are promising candidates for producing photoactive materials because these d¹⁰ metal ions not only possess a variety of coordination numbers and geometries, but also exhibit luminescence properties when bound to functional ligands. It is difficult to predict the final structure of such polymers because the assembly process is influenced by many subtle factors. Bis(imidazol‐1‐yl)‐substituted alkane/benzene molecules are good bridging ligands because their flexibility allows them to bend and rotate when they coordinate to metal centres. Two new Zn^II and Cd^II coordination polymers based on mixed ligands, namely, poly[[μ₂‐1,4‐bis(imidazol‐1‐ylmethyl)benzene‐κ²N³:N^3′]bis(μ₃‐2,2‐dimethylbutanoato‐κ³O¹:O⁴:O^4′)dizinc(II)], [Zn₂(C₆H₈O₄)₂(C₁₄H₁₄N₄)]_n, and poly[[μ₂‐1,4‐bis(imidazol‐1‐ylmethyl)benzene‐κ²N³:N^3′]bis(μ₃‐2,2‐dimethylbutanoato‐κ⁵O¹,O^1′:O⁴,O^4′:O⁴)dicadmium(II)], [Cd₂(C₆H₈O₄)₂(C₁₄H₁₄N₄)]_n, have been synthesized under hydrothermal conditions and characterized by single‐crystal X‐ray diffraction, elemental analysis, IR spectroscopy and thermogravimetric analysis. Both complexes crystallize in the monoclinic space group C2/c with similar unit‐cell parameters and feature two‐dimensional structures formed by the interconnection of S‐shaped Zn(Cd)–2,2‐dimethylsuccinate chains with 1,4‐bis(imidazol‐1‐ylmethyl)benzene bridges. However, the Cd^II and Zn^II centres have different coordination numbers and the 2,2‐dimethylsuccinate ligands display different coordination modes. Both complexes exhibit a blue photoluminescence in the solid state at room temperature.     

Sesquialkoxide von Gallium und Indium

Sesquialkoxides of Gallium and Indium Treatment of GaMe₃ with one equivalent of HO^cHex in toluene at 20 °C leads to [Me₂GaO^cHex]₂ ( 4 ) under evolution of methane. The reaction of InMe₃ with two equivalents of HO^cHex leads under similar conditions not to [MeIn(O^cHex)₂]_n but to the sesquialkoxide [In{Me₂In(O^cHex)₂}₃] ( 5 ). 5 can be described also as [{Me₂InO^cHex)}₂{MeIn(O^cHex)₂}₂]. The use of an excess of cyclohexanol in boiling toluene gives the same result. Under these reflux conditions, the reaction of GaMe₃ with an excess of PhCH₂OH leads exclusively to another type of sequialkoxides, [Ga{MeGa(OCH₂Ph)₃}₃] ( 6 ). 4 — 6 were characterized by NMR, vibrational and MS spectra, as well as by X‐ray structure determinations. According to this, 4 forms centrosymmetrical and therefore planar Ga₂O₂ four‐membered rings. 5 and 6 possess basically the same structural motif, central M³⁺ ion ( 5 : In³⁺; 6 : Ga³⁺) coordinated by three metalate units ( 5 : [Me₂In(O^cHex)₂]^—; 6 : [MeGa(OCH₂Ph)₃]^—). The central M³⁺ ions have always coordination number (CN) six while the three surrounding metal ions possess CN 4. Because of the spectroscopic findings 6 must exist in two isomers (1:1). The C₃‐symmetrical isomer C₃‐ 6 was characterized by X‐ray analysis, while the isomer C₁‐ 6 could by described mainly by the complex NMR data.     

Two different anionic manganese(II) coordination polymers constructed through dicyanamide coordination bridges

In order to explore new metal coordination polymers and to search for new types of ferroelectrics among hybrid coordination polymers, two manganese dicyanamide complexes, poly[tetramethylammonium [di‐μ₃‐dicyanamido‐κ⁶N¹:N³:N⁵‐tri‐μ₂‐dicyanamido‐κ⁶N¹:N⁵‐dimanganese(II)]], {[(CH₃)₄N][Mn₂(NCNCN)₅]}_n, (I), and catena‐poly[bis(butyltriphenylphosphonium) [[(dicyanamido‐κN¹)manganese(II)]‐di‐μ₂‐dicyanamido‐κ⁴N¹:N⁵]], {[(C₄H₉)(C₆H₅)₃P]₂[Mn(NCNCN)₄]}_n, (II), were synthesized in aqueous solution. In (I), one Mn^II cation is octahedrally coordinated by six nitrile N atoms from six anionic dicyanamide (dca) ligands, while the second Mn^II cation is coordinated by four nitrile N atoms and two amide N atoms from six anionic dca ligands. Neighbouring Mn^II cations are linked together by μ‐1,5‐ and μ‐1,3,5‐bridging dca anions to form a three‐dimensional polymeric structure. The anionic framework exhibits a solvent‐accessible void of 289.8 ų, amounting to 28.0% of the total unit‐cell volume. Each of the cavities in the network is occupied by only one tetramethylammonium cation. In (II), each Mn^II cation is octahedrally coordinated by six nitrile N atoms from six dca ligands. Neighbouring Mn^II cations are linked together by double dca bridges to form a one‐dimensional polymeric chain, and C—H...N hydrogen‐bonding interactions are involved in the formation of the one‐dimensional layer structure.     

Synthesis,Persistent Luminescence,and Thermoluminescence Properties of Yellow Sr3SiO5:Eu2+,RE3+ (RE=Ce,Nd, Dy,Ho, Er,Tm, Yb) and Orange‐Red Sr3−xBaxSiO5:Eu2+, Dy3+ Phosphor

Sunlight‐excitable orange or red persistent oxide phosphors with excellent performance are still in great need. Herein, an intense orange‐red Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ persistent luminescence phosphor was successfully developed by a two‐step design strategy. The XRD patterns, photoluminescence excitation and emission spectra, and the thermoluminescence spectra were investigated in detail. By adding non‐equivalent trivalent rare earth co‐dopants to introduce foreign trapping centers, the persistent luminescence performance of Eu²⁺ in Sr₃SiO₅ was significantly modified. The yellow persistent emission intensity of Eu²⁺ was greatly enhanced by a factor of 4.5 in Sr₃SiO₅:Eu²⁺,Nd³⁺ compared with the previously reported Sr₃SiO₅:Eu²⁺, Dy³⁺. Furthermore, Sr ions were replaced with equivalent Ba to give Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ phosphor, which shows yellow‐to‐orange‐red tunable persistent emissions from λ=570 to 591 nm as x is increased from 0 to 0.6. Additionally, the persistent emission intensity of Eu²⁺ is significantly improved by a factor of 2.7 in Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ (x=0.2) compared with Sr₃SiO₅:Eu²⁺,Dy³⁺. A possible mechanism for enhanced and tunable persistent luminescence behavior of Eu²⁺ in Sr_3?xBa_xSiO₅:Eu²⁺,RE³⁺ (RE=rare earth) is also proposed and discussed.     

A mixed‐valence copper coordination polymer generated by a hydrothermal metal/ligand redox reaction process

The title coordination polymer, poly[(μ₄‐2‐oxidoisophthalato‐κ⁶O¹,O²:O²,O³:O^3′:O^3′)(μ₂‐quinoxaline‐κ²N:N′)copper(I)copper(II)], [Cu₂(C₈H₃O₅)(C₈H₆N₂)]_n, contains two crystallographically distinct Cu ions, one quinoxaline (QA) unit and one 2‐oxidoisophthalate trianion (L) derived from 2‐hydroxyisophthalic acid (H₃L). The Cu^II ion is strongly coordinated by four O atoms in a distorted square geometry, of which two belong to two phenoxide groups and the other two to carboxylate groups of two L ligands. In addition, the Cu^II cation interacts weakly with a symmetry‐related carboxylate O atom which belongs to the L ligand in an adjacent layer, giving a square‐pyramidal coordination geometry. The Cu^I ion is trigonally coordinated by two N atoms from two QA molecules and one O atom from an L carboxylate group. The Cu^I centres are bridged by QA ligands to give a chain along the c axis. Two Cu^II ions and two L ligands form a [Cu₂L₂]²⁻ `metallo‐ligand', which coordinates two Cu^I ions. Thus, the chains of Cu^I and QA are linked by the [Cu₂L₂]²⁻ metallo‐ligand to yield a two‐dimensional (6,3) sheet. These sheets are further linked by symmetry‐related carboxylate O atoms of neighbouring layers into a three‐dimensional framework. The in situ reaction from benzene‐1,2,3‐tricarboxylic acid (H₃L1) to L in the present system has rarely been observed before, although a few novel in situ reactions, such as ligand oxidative coupling, hydrolysis and substitution, have been observed during the hydrothermal process.     

Viscoelasticity and birefringence of polyisoprene

The complex Young's modulus, E^*(ω), and the complex strain-optical coefficient, O^*(ω), which is the ratio of the birefringence to the strain, were measured for polyisoprene (PIP) over a frequency range of 1 ～ 130 Hz and a temperature range of 22 ～ ?100°C. The imaginary part of O^*, O″, was positive at low frequencies and negative at high frequencies. The real part, O′, was always positive and showed a maximum. The complicated behavior of O^* could be understood by the assumption that E^* = E_R^* + E_G^* and O^* = C_RE_R^* + C_GE_G^*, where E_R^* and E_G^* were complex quantities and C_R and C_G were constants. The C_R value, equal to the ordinary stress-optical coefficient measured in the rubbery plateau zone, was 2.0 × 10^?9 Pa^?1. The C_G value, defined as the ratio O″/E″ in the glassy zone, was ?1.1 × 10^?11 Pa^?1. The E_G^*, which was the major component of E^* in the glassy zone, showed almost the same frequency dependence as that of polystyrene and polycarbonate. The E_R^*, which was dominant in the rubbery zone, was described well by the bead-spring theory. The temperature dependence of the E_G^* was stronger than that of the E_R^*. This difference caused the breakdown of the thermorheological simplicity for E^* and O^* around the glass-to-rubber transition zone. © 1995 John Wiley & Sons, Inc.     

Synthesis and Characterization of trans‐PdII Trimethylsilylchalcogenolates

The trans‐bis(trimethylsilyl)chalcogenolate palladium complexes, trans‐[Pd(ESiMe₃)₂(PnBu₃)₂] [E = S ( 1 ) and Se ( 2 )] were synthesized in good yields and high purity by reacting trans‐[PdCl₂(PBu₃)₂] with LiESiMe₃ (E = S, Se), respectively. These complexes were characterized by ¹H, ¹³C{¹H}, ³¹P{¹H} (and ⁷⁷Se{¹H}) NMR spectroscopy and single‐crystal X‐ray analysis. The reaction of 2 with propionyl chloride led to the formation of trans‐[Pd(SeC(O)CH₂CH₃)₂(PnBu₃)₂] ( 3 ), a trans‐bis(selenocarboxylato) palladium complex and thus established a new method for the formation of this type of complex. Complex 3 was characterized by ¹H, ¹³C{¹H}, ³¹P{¹H} and ⁷⁷Se{¹H} NMR spectroscopy and a single‐crystal X‐ray structure analysis.     

Formation of an Azaruthenacyclopentadiene Skeleton via Ammonia Activation by an Electron-Deficient Ru3 Cluster

A dicationic triruthenium complex containing a μ₃-η³-C₃ ring, [(Cp*Ru)₃(μ₃-η³-C₃MeH₂−)(μ₃-CH)(μ-H)]²⁺ ( 1 a , Cp*=η⁵-C₅Me₅), reacted with ammonia to yield a μ-amido complex, [(Cp*Ru)₃(μ₃-η³-CHCMeCH) (μ₃-CH)(μ-NH₂)]²⁺ ( 5 ), via N−H bond scission. Subsequent treatment with base resulted in C−N bond formation to yield a μ₃-η²:η²-1-azabutadien-4-yl complex, [(Cp*Ru)₃(μ₃-CH)(μ₃-η²:η²-NH=CH−CMe=CH−)]⁺ ( 6 a ). The azaruthenacyclopentadiene skeleton was alternatively synthesized by the photolysis of mono-cationic complex [(Cp*Ru)₃(μ₃-η³-C₃RH₂−)(μ₃-CH)]⁺ ( 2 a ; R=Me, 2 b ; R=H) in the presence of ammonia. The C₃ ring skeleton was broken via the electron transfer to the π*(C−C) orbital in the C₃ ring, and a transiently generated unsaturated μ₃-allylic species can take up ammonia, resulting in N−H bond scission followed by C−N bond formation.     

Heterodinuclear M1M2 Complexes (M1=Ni,Pd, Pt; M2=Rh,Ir) Supported by a Tetradentate Phosphine Ligand and Their Application for Hydrosilylation

A new series of cationic heterodinuclear complexes, [M¹M²Cl₂(meso-dpmppp)(RNC)₂]PF₆ (M¹=Ni, M²=Rh, R=^tBu ( 1 a ); M¹=Pd, M²=Rh, R=^tBu ( 2 a ), Xyl ( 2 b ); M¹=Pt, M²=Rh, R=^tBu ( 3 a ), Xyl ( 3 b ); M¹=Pd, M²=Ir, R=^tBu ( 4 a )), supported by a tetradentate phosphine ligand, meso-Ph₂PCH₂P(Ph)(CH₂)₃P(Ph)CH₂PPh₂ (meso-dpmppp), were synthesized by stepwise reactions of meso-dpmppp with NiCl₂ ⋅ 6H₂O or MCl₂(cod) (M=Pd, Pt), forming mononuclear metalloligands of [M¹Cl₂(meso-dpmppp)], and with [M²Cl(cod)]₂ (M²=Rh, Ir) and RNC (R=^tBu, Xyl) in the presence of [NH₄][PF₆]. The related neutral PdRh complex, [PdRhCl₃(meso-dpmppp)(XylNC)] ( 5 ), was also prepared. The structures of 1 – 5 were determined by X-ray analyses to contain two square planar d⁸ metal centers with face-to-face arrangement, where meso-dpmppp supports M¹ and M² metal ions in cis/trans-P,P coordination mode, combining cis-{M¹P₂Cl₂} and trans-{M²P₂(CNR)₂} units. Complexes 1 – 4 showed an intence characteristic absorption around 422–464 nm derived from Rh^I→RNC MLCT transition (HOMO→LUMO+1), which are influenced by changing M¹ (Ni^II, Pd^II, Pt^II) metal ions since HOMO composed of dσ* orbitals appreciably destabilized by changing M¹ from Ni to Pd, and Pt. The electronic structures of 1 a – 4 a were investigated on the basis of DFT calculations and NBO analyses to show weak but noticeable d⁸–d⁸ metallophilic interaction as empirical dispersion energy of 0.9–1.5 kcal/mol without M¹–M² covalent bonding interaction. In addition, 1 – 5 were utilized as catalysts for hydrosilylation of styrene, and the NiRh complex 1 a was found to show higher activity and chemo- and regioselectivity compared with 2 – 5 .     

Tetraalkylammonium Picrates in the Dichloromethane–Water System: Ion-Pair Formation and Liquid–Liquid Distribution of Free Ions and Ion Pairs

Equilibria concerning picrates of tetraalkylammonium ions (Me₄N⁺, Et₄N⁺, Pr₄N⁺, Bu₄N⁺, Bu₃MeN⁺) in a dichloromethane−water system have been investigated at 25 ^∘C. The 1:1 ion-pair formation constants (K _IP,o ^o) in dichloromethane at infinite dilution were conductometrically determined. The distribution constants (K _D ^o) of the ion pairs and the free cations between the solvents were determined by a batch-extraction method. The K _IP,o ^o value varies in the cation sequence, Bu₄N⁺ ≈ Pr₄N⁺ ≈ Et₄N⁺ < Bu₃MeN⁺ < < Me₄N⁺; this trend is explained by the electrostatic cation−anion interaction taking into account the structures of the ion pairs determined by density functional theory calculations. For the ion pairs of the symmetric R₄N⁺ cations, there is a linear positive relationship between log₁₀ K _D ^o and the number of methylene groups in the cation (N _{CH 2}). The ion pair of asymmetric Bu₃MeN⁺ has a higher distribution constant than that expected from the above log₁₀ K _D ^o versus N _{CH 2} relationship. These cation dependencies of log₁₀ K _D ^o for the ion pairs are explained theoretically by using the Hildebrand-Scatchard equation. For all the cations, the log₁₀ K _D ^o value of the free cation increases linearly with N _{CH 2}; the variation of log₁₀ K _D ^o is discussed by decomposing the distribution constant into the Born-type electrostatic contribution and the non-Born one, and attributed to the latter that is governed by the differences in the molar volumes of the cations. The cation dependencies of the ion-pair extractability and ion pairing in water are also discussed. An erratum to this article can be found at     

exo/endo-Selectivity in the Reaction of ‘Bare’ FeO+ with Bicyclo[2.2.1]heptane (Norbornane)

‘Bare’ FeO⁺ reacts in the gas phase with norbornane with collision efficiency, and the most prominent cationic products correspond to [FeC₅H₆]⁺ (32%), [FeC₇H₈]⁺ (19%), [FeC₃H₆O]⁺ (19%) and [FeC₆H₆]⁺ (14%), which are structurally characterized by ligand exchange as well as collision-induced dissociation experiments. Circumstantial evidence is provided which indicates that the complexes [FeC₅H₆]⁺, [FeC₇H₈]⁺, and [FeC₆H₆]⁺ originate from an Fe(norbornene)⁺ intermediate which itself is formed by elimination of H₂O from the [FeO(norbornane)]⁺ encounter complex. Although the reactions are preceded and/or accompanied by partial H/D exchange, the isotope distribution in the productions clearly points to a preferential endo-attack of bare FeO⁺, with an endo/exo-ratio of ca. 10.3 and kinetic isotope effects k_H/k_D for the endo-abstraction of 2.4 and of 7.7 for approaching an exo-C? H bond. The preferred endo-approach of bicyclo[2.2.1]heptane by ‘bare’ FeO⁺ is in distinct contrast to the P-450-mediated or the iron(III)porphyrin-catalyzed hydroxylation of this substrate which favor reactions at the exo-face.     

Analysis of chemical bonding in C2 using Dyson orbitals

Multireference configuration interaction wave functions with single and double excitations were calculated for the ¹Σ⁺_g ground state of the C₂ molecule and the excited states of C⁺₂ with symmetries ²Σ⁺_g, ²Σ^-_u, ²Π_u, and ²Π_g. The corresponding σ_g, σ_u, π_u, and π_g valence Dyson orbitals were calculated. Most of the density due to the valence electrons is accounted for by three σ_g, one σ_u, and one degenerate pair of π_u Dyson orbitals. Electron correlation plays an important role in the bond strength of C₂ by increasing the occupation of the σ_g valence orbitals and decreasing the occupation of the σ_u and π_u valence orbitals. © 1996 John Wiley & Sons, Inc.     

Reactivity of Oxygen Radical Anions Bound to Scandia Nanoparticles in the Gas Phase: CH Bond Activation

The activation of C?H bonds in alkanes is currently a hot research topic in chemistry. The atomic oxygen radical anion (O^?.) is an important species in C?H activation. The mechanistic details of C?H activation by O^?. radicals can be well understood by studying the reactions between O^?. containing transition metal oxide clusters and alkanes. Here the reactivity of scandium oxide cluster anions toward n‐butane was studied by using a high‐resolution time‐of‐flight mass spectrometer coupled with a fast flow reactor. Hydrogen atom abstraction (HAA) from n‐butane by (Sc₂O₃)_NO^? (N=1–18) clusters was observed. The reactivity of (Sc₂O₃)_NO^? (N=1–18) clusters is significantly sizedependent and the highest reactivity was observed for N=4 (Sc₈O₁₃^?) and 12 (Sc₂₄O₃₇^?). Larger (Sc₂O₃)_NO^? clusters generally have higher reactivity than the smaller ones. Density functional theory calculations were performed to interpret the reactivity of (Sc₂O₃)_NO^? (N=1–5) clusters, which were found to contain the O^?. radicals as the active sites. The local charge environment around the O^?. radicals was demonstrated to control the experimentally observed size‐dependent reactivity. This work is among the first to report HAA reactivity of cluster anions with dimensions up to nanosize toward alkane molecules. The anionic O^?. containing scandium oxide clusters are found to be more reactive than the corresponding cationic ones in the C?H bond activation.     

Hydrolysis of Methylphenyldiethoxysilane with Rare Earth Superacid Catalysts SO2− 4/TiO2/Ln3+

Abstract

An environmentally benign hydrolysis of methylphenyldiethoxysilane (MePhSi(OEt)₂) catalyzed by a rare earth superacid catalyst SO ^2? ₄ /TiO₂/Ln³⁺ has been investigated. The hydrolysis rates decrease in the order SO ^2? ₄ /TiO₂/Nd³⁺ > SO ^2? ₄ /TiO₂/Y³⁺ > SO ^2? ₄ /TiO₂/Sm³⁺ > SO ^2? ₄ /TiO₂. The hydrolysis of MePhSi(OEt)₂ is a first-order reaction with respect to the concentration of MePhSi(OEt)₂, and the hydrolysis rate constant increases with increasing temperature. The activation energy E _a and the pre-exponential factor for this hydrolysis catalyzed by SO ^2? ₄ /TiO₂/Nd³⁺ have been determined as 322.50 kJ mol^?1 and 7.12 × 10⁴¹ s^?1, respectively. The products of the hydrolysis are oligomers of polymethylphenylsiloxane. The mechanism of MePhSi(OEt)₂ hydrolysis is also discussed.     

Sr,Ba and Cd arsenates with the apatite‐type structure

X‐ray diffraction analysis of single crystals of three new arsenates adopting apatite‐type structures yielded formula Sr₅(AsO₄)₃F for strontium arsenate fluoride, (I), (Sr_1.66Ba_0.34)(Ba_2.61Sr_0.39)(AsO₄)₃Cl for strontium barium arsenate chloride, (II), and Cd₅(AsO₄)₃Cl_0.58(OH)_0.42 for cadmium arsenate hydroxide chloride, (III). All three structures are built up of isolated slightly distorted AsO₄ tetrahedra that are bridged by Sr²⁺ in (I), by Sr²⁺/Ba²⁺ in (II) and by Cd²⁺ in (III). Compounds (I) and (II) represent typical fluorapatites and chlorapatites, respectively, with F⁻ at the 2a (0, 0, ) site and Cl⁻ at the 2b (0, 0, 0) site of P6₃/m. In contrast, in (III), due to the requirement that the smaller Cd²⁺ cation is positioned closer to the channel Cl⁻ anion (partially substituted by OH⁻), the anion occupies the unusual 2a (0, 0, ) site. Therefore, Cl⁻ is similar to F⁻ in (I), coordinated by three A2 cations, unlike the octahedrally coordinated Cl⁻ in (II) and other ordinary chlorapatites. Furthermore, in (III), using FT–IR studies, we have inferred the existence of H⁺ outside the channel in oxyhydroxyapatites and provided possible atomic coordinates for a H atom in HAsO₄²⁻, leading to a proposed formulation of the compound as Cd₅(AsO₄)_3−x(HAsO₄)_xCl_0.58(OH)_{0.42−x−(y/2)}O_x+(y/2)□_y/2.     

Preparation and Crystal Structures of the Hydrous Mercury Tellurates,HgII(H4TeVIO6) and HgI2(H4TeVIO6)(H6TeVIO6)·2H2O

Single crystals of Hg^II(H₄Te^VIO₆) (colourless to light‐yellow, rectangular plates) and Hg^I₂(H₄Te^VIO₆)(H₆Te^VIO₆)·2H₂O (colourless, irregular) were grown from concentrated solutions of orthotelluric acid, H₆TeO₆, and respective solutions of Hg(NO₃)₂ and Hg₂(NO₃)₂. The crystal structures were solved and refined from single crystal diffractometer data sets (Hg^II(H₄Te^VIO₆): space group Pna2₁, Z = 4, a =10.5491(17), b = 6.0706(9), c = 8.0654(13)Å, 1430 structure factors, 87 parameters, R[F² > 2σ(F²)] = 0.0180; Hg^I₂(H₄Te^VIO₆)(H₆Te^VIO₆)·2H₂O: space group P1¯, Z = 1, a = 5.7522(6), b = 6.8941(10), c = 8.5785(10)Å, α = 90.394(8), β = 103.532(11), γ = 93.289(8)°, 2875 structure factors, 108 parameters, R[F² > 2σ(F²)] = 0.0184). The structure of Hg^II(H₄Te^VIO₆) is composed of ribbons parallel to the b axis which are built of [H₄TeO₆]^2— anions and Hg²⁺ cations held together by two short Hg—O bonds with a mean distance of 2.037Å. Interpolyhedral hydrogen bonding between neighbouring [H₄TeO₆]^2— groups, as well as longer Hg—O bonds between Hg atoms of one ribbon to O atoms of adjacent ribbons lead, to an additional stabilization of the framework structure. Hg^I₂(H₄Te^VIO₆)(H₆Te^VIO₆)·2H₂O is characterized by a distorted hexagonal array made up of [H₄TeO₆]^2— and [H₆TeO₆] octahedra which spread parallel to the bc plane. Interpolyhedral hydrogen bonding between both building units stabilizes this arrangement. Adjacent planes are stacked along the a axis and are connected by Hg₂²⁺ dumbbells (d(Hg—Hg) = 2.5043(4)Å) situated in‐between the planes. Additional stabilization of the three‐dimensional network is provided by extensive hydrogen bonding between interstitial water molecules and O and OH‐groups of the [H₄TeO₆]^2— and [H₆TeO₆] octahedra. Upon heating Hg^I₂(H₄Te^VIO₆)(H₆Te^VIO₆)·2H₂O decomposes into TeO₂ under formation of the intermediate phases Hg^II₃Te^VIO₆ and the mixed‐valent Hg^IITe^IV/VI₂O₆.     

Additivity Factors in the Binding of the Diethyltin(IV) Cation by Ligands Containing Amino and Carboxylic Groups at Different Ionic Strengths

Complex formation constants were determined potentiometrically (by a ISE-H⁺, glass electrode) in the systems, M²⁺ – L^z – H⁺ [M²⁺ = (C₂H₅)₂Sn²⁺, L^z = malonate, glycinate and ethylenediamine] at t = 25 ^∘C and 0.1 mol-L⁻¹≤ I/ ≤ 1 mol-L⁻¹ in NaCl_aq (0.1 mol-L⁻¹ ≤ I ≤ 0.75 mol-L⁻¹ for the ethylenediamine system). Thermodynamic values of formation constants, at infinite dilution, are [± 95% confidence interval, ^Tβ_pqr refer to the equilibrium, pM²⁺ + qL^z + rH⁺ = M_pL_qH_r^(2+z+r)]: for malonate, log₁₀ ^Tβ₁₁₀ = (5.47 ± 0.10); for glycinate, log₁₀ ^Tβ₁₁₀ = (9.54 ± 0.08), log₁₀ ^Tβ₁₁₁ = (12.97 ± 0.10); and for ethylenediamine, log₁₀ ^Tβ₁₁₀ = (10.47 ± 0.10), log₁₀ ^Tβ₁₂₀ = (16.17 ± 0.12) and log₁₀ ^Tβ₁₁₁ = (15.46 ± 0.10). The dependence on ionic strength of the formation constants was modeled by a simple Debye–Hückel type equation and by the SIT approach. By analyzing the stability of the species in the three different systems we found a simple additivity rule that can be expressed by the relationship: log₁₀ K = 6.46 n_N + 3.96 n_O − 0.60 (n_N²+ n_O²), with a mean deviation, ε(log₁₀ K) = 0.15 (K = equilibrium constant for the interaction of the organometal cation with the unprotonated or protonated ligand, n_N = number of amino groups and n_O = number of carboxylic groups of the ligand(s) involved in the formation reaction of complex species).