Controlling the Catalytic Properties of Copper-Containing Oxide Catalysts

The results of a systematic study of the formation of Cu–Zn, Cu–Zn–Al, Cu–Zn–Cr, Cu–Zn–Si, Cu–Cr, and Cu–Si oxide catalysts with a widely varied ratio between their components are generalized within the chemical approach developed by G.K. Boreskov to establish the quantitative relation between their chemical composition and catalytic activity. Simultaneously, their catalytic properties, such as selectivity and activity, are measured under the same conditions in the methanol synthesis and dehydrogenation and water gas shift reactions, whose common feature is a reductive reaction medium. The activity of Cu–Zn–Al–Cr— Si-oxide catalysts in all the studied reactions is governed by the Cu⁰ nanoparticles formed on their surface in the process of reductive activation. Nanoparticles of different catalysts have similar sizes (3–8 nm). However, the ratios between the catalytic activities per unit of the copper surface area for catalysts with various structures of their oxide support (spinel, wurtzite, zincsilite, or silica type) are appreciably different in each reaction. The relation between the chemical composition of a catalyst and its catalytic activity in a certain reaction is established by the chemical composition of its precursor representing a hydroxo compound, i.e., the nature of the selected cations and the quantitative ratio between them. The decomposition of hydroxo compounds to oxides (and the further activation of oxides) should be performed at medium temperatures, providing the incomplete elimination of ОН^– and CO₃^2- anions, i.e., the formation of anion-modified oxides. The structure of the latter and the type of interaction between Cu⁰ nanoparticles and an oxide support are governed by the structure of the hydroxo precursor compound.     

Monomeric Copper(II) Sites Supported on Alumina Selectively Convert Methane to Methanol

Monomeric Cu^II sites supported on alumina, prepared using surface organometallic chemistry, convert CH₄ to CH₃OH selectively. This reaction takes place by formation of CH₃O surface species with the concomitant reduction of two monomeric Cu^II sites to Cu^I, according to mass balance analysis, infrared, solid‐state nuclear magnetic resonance, X‐ray absorption, and electron paramagnetic resonance spectroscopy studies. This material contains a significant fraction of Cu active sites (22 %) and displays a selectivity for CH₃OH exceeding 83 %, based on the number of electrons involved in the transformation. These alumina‐supported Cu^II sites reveal that C?H bond activation, along with the formation of CH₃O‐ surface species, can occur on pairs of proximal monomeric Cu^II sites in a short reaction time.     

Highly Selective CO2 Electroreduction to CH4 by In Situ Generated Cu2O Single-Type Sites on a Conductive MOF: Stabilizing Key Intermediates with Hydrogen Bonding

It is still a great challenge to achieve high selectivity of CH₄ in CO₂ electroreduction reactions (CO₂RR) because of the similar reduction potentials of possible products and the sluggish kinetics for CO₂ activation. Stabilizing key reaction intermediates by single type of active sites supported on porous conductive material is crucial to achieve high selectivity for single product such as CH₄. Here, Cu₂O(111) quantum dots with an average size of 3.5 nm are in situ synthesized on a porous conductive copper-based metal–organic framework (CuHHTP), exhibiting high selectivity of 73 % towards CH₄ with partial current density of 10.8 mA cm⁻² at −1.4 V vs. RHE (reversible hydrogen electrode) in CO₂RR. Operando infrared spectroscopy and DFT calculations reveal that the key intermediates (such as *CH₂O and *OCH₃) involved in the pathway of CH₄ formation are stabilized by the single active Cu₂O(111) and hydrogen bonding, thus generating CH₄ instead of CO.     

超临界水中醋酸锌水解反应的分子动力学模拟

氧化锌(ZnO)是一种重要的化工原料, 超临界水热合成法制备纳米ZnO的第一步是锌盐与碱或水发生水解反应生成Zn(OH)₂, 后者接着脱水生成ZnO. 以Zn(CH₃COO)₂为原料, 直接和超临界水(SCW)反应能够制备纳米级的ZnO颗粒, 但对反应机理的探讨较少. 本研究利用分子动力学模拟超临界条件下Zn(CH₃COO)₂水解反应过程中的结构和能量变化, 发现Zn(CH₃COO)₂在SCW中容易聚集成无定形的团簇, 1个Zn²⁺平均和5个CH₃COO^-和1个H₂O配位, 形成6配位的八面体结构. 处于Zn(CH₃COO)₂团簇和SCW界面的Zn²⁺能够和更多的H₂O配位. 水解反应后系统的势能降低, 同时伴随Zn(CH₃COO)₂团簇结构的改变. 反应产物OH^-分布在Zn(CH₃COO)₂团簇内部, 富集Zn²⁺, 而CH₃COOH则分布在SCW中. 本文的工作为超临界水热合成的反应过程提供了基本的理论依据.     

Adsorption properties of silica-based sorbents containing phosphonic acid residues

Isotherms are measured for nitrogen, n-hexane, triethylamine, and water vapor adsorption on silicas of different origins, the surface layers of which contain functional groups of the ??Si(CH₂)₂P(O)(OH)₂ composition, namely, ethylene- and phenylene-bridged polysilsesquioxane xerogels produced by the sol-gel method, silica microspheres synthesized from tetraethoxysilane in the presence of [CH₃(CH₂)₁₇N(CH₃)₃]Br as a template by spray-drying method, and SBA-15 mesoporous silica produced based on tetraethoxysilane using Pluronic 123 as a template. It is shown that all of the samples possess high specific surface areas, while the types of adsorption isotherms and the accessibility of active acidic sites for adsorption interactions with electron-donor molecules depend on the structures of pores and surface layers, which are governed by the methods of synthesis and postsynthesis sample treatment.     

Thermally Induced Silane Dehydrocoupling on Silicon Nanostructures

Organic trihydridosilanes can be grafted to hydrogen‐terminated porous Si nanostructures with no catalyst. The reaction proceeds efficiently at 80 °C, and it shows little sensitivity to air or water impurities. The modified surfaces are stable to corrosive aqueous solutions and common organic solvents. Octadecylsilane H₃Si(CH₂)₁₇CH₃, and functional silanes H₃Si(CH₂)₁₁Br, H₃Si(CH₂)₉CH=CH₂, and H₃Si(CH₂)₂(CF₂)₅CF₃ are readily grafted. When performed on a mesoporous Si wafer, the perfluoro reagent yields a superhydrophobic surface (contact angle 151°). The bromo‐derivative is converted to azide, amine, or alkyne functional surfaces via standard transformations, and the utility of the method is demonstrated by loading of the antibiotic ciprofloxaxin (35 % by mass). When intrinsically photoluminescent porous Si films or nanoparticles are used, photoluminescence is retained in the grafted products, indicating that the chemistry does not introduce substantial nonradiative surface traps.     

Triethylphosphanimin-Komplexe der Acetate von Kupfer(II) und Zink. Kristallstrukturen von [Zn(O2C–CH3)2(HNPEt3)], [Cu5(O2C–CH3)10(HNPEt3)2] und [Cu(O2C–CH3)2(HNPEt3)2]

Triethylphosphanimine Complexes of the Acetates of Copper(II) and Zinc. Crystal Structures of [Zn(O₂C–CH₃)₂(HNPEt₃)], [Cu₅(O₂C–CH₃)₁₀(HNPEt₃)₂], and [Cu(O₂C–CH₃)₂(HNPEt₃)₂] The title compounds originate from the anhydrous acetates of zinc and copper(II) with trimethylsilyl-triethylphosphanimine, Me₃SiNPEt₃, in the presence of water in dichloromethane. They form colourless ( 1 ), bluish-green ( 2 ), and blue ( 3 ), respectively, single crystals, which were characterized by IR spectroscopy and by crystal structure analyses. [Zn(O₂C–CH₃)₂(HNPEt₃)] ( 1 ): Space group P 4 2₁c, Z = 8, lattice dimensions at –83 °C: a = b = 1709.6(2), c = 982.4(1) pm, R = 0.0551. 1 has a polymeric chain structure in which the zinc atoms are μ₂-bridged via the oxygen atoms of one of the two acetato groups, while the second acetato group and the phosphanimine are bonded terminally. [Cu₅(O₂C–CH₃)₁₀(HNPEt₃)₂]( 2 · 4 CH₂Cl₂): Space group P2₁/c, Z = 8, lattice dimensions at –80 °C: a = 1761.18(13), b = 4074.5(2), c = 1733.34(15) pm, β = 91.383(10)°, R = 0.0413. 2 consists of the two structural units [Cu₂(O₂C–CH₃)₄] and [Cu₃(O₂C–CH₃)₆(HNPEt₃)₂], which are connected via two of the acetato groups of the Cu₃-unit along the crystallographic a-axis to form three crystallographically independent polymeric strands. [Cu(O₂C–CH₃)₂(HNPEt₃)₂] ( 3 ): Space group P2₁/n, Z = 2, lattice dimensions at 20 °C: a = 695.49(8), b = 1217.85(10), c = 1380.05(7) pm, β = 96.451(7)°, R = 0.0291. 3 forms monomeric, centrosymmetric molecules with a square planar environment at the Cu atoms.     

A comparative theoretical study of the reactivities of the Al+ and Cu+ ions toward methylamine and dimethylamine

A very recent laser ablation‐molecular beam experiment shows that an Al⁺ ion can react with a single methylamine (MA, CH₃NH₂) or dimethylamine (DMA, (CH₃)₂NH) molecule to form a 1:1 ion–molecule complex Al⁺[CH₃NH₂] or Al⁺[(CH₃)₂NH)], whereas a dehydrogenated complex ion Cu⁺[CH₃N] or Cu⁺[C₂H₅N] is detected, respectively, in the similar reaction for a Cu⁺ ion. Here, we show a comparative density functional theory study for the reactivities of the Al⁺ and Cu⁺ ions toward MA and DMA to reveal the intrinsic mechanism. It is found that the interactions of the Al⁺ ion with MA and DMA are mostly electrostatic, leading to the direct ion–molecule complexes, Al⁺? NH₂CH₃ and Al⁺? NH( CH₃)₂, in contrast to the non‐negligible covalent character in the corresponding Cu⁺‐containing complexes, Cu⁺? NH₂CH₃ and Cu⁺? NH( CH₃)₂. The general dehydrogenation mechanism for MA and DMA promoted by the Cu⁺ ion has been shown, and the preponderant structures contributing to the mass spectra of the product ions Cu⁺[CH₃N] and Cu⁺[C₂H₅N] are rationalized as Cu⁺? NHCH₂ and Cu⁺? N( CH₂)( CH₃). The presumed dehydrogenation reactions are also discussed for the Al⁺‐containing systems. However, the involved barriers are found to be too high to be overcome at low energy conditions. These results have rationalized all the experimental observations well. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Selective methane chlorination to methyl chloride by zeolite Y-based catalysts

The CH₄ chlorination over Y zeolites was investigated to produce CH₃Cl in a high yield. Three different catalytic systems based on Y zeolite were tested for enhancement of CH₄ conversion and CH₃Cl selectivity: (i) HY zeolites in H⁺-form having various Si/Al ratios, (ii) Pt/HY zeolites supporting Pt metal nanoparticles, (iii) Pt/NaY zeolites in Na⁺-form supporting Pt metal nanoparticles. The reaction was carried out using the gas mixture of CH₄ and Cl₂ with the respective flow rates of 15 and 10 mL min⁻¹ at 300–350 °C using a fixed-bed reactor under a continuous gas flow condition (gas hourly space velocity = 3000 mL g⁻¹ h⁻¹). Above the reaction temperature of 300 °C, the CH₄ chlorination is spontaneous even in the absence of catalyst, achieving 23.6% of CH₄ conversion with 73.4% of CH₃Cl selectivity. Under sufficient supplement of thermal energy, Cl₂ molecules can be dissociated to two chlorine radicals, which triggered the C-H bond activation of CH₄ molecule and thereby various chlorinated methane products (i.e., CH₃Cl, CH₂Cl₂, CHCl₃, CCl₄) could be produced. When the catalysts were used under the same reaction condition, enhancement in the CH₄ conversion was observed. The Pt-free HY zeolite series with varied Si/Al ratios gave around 27% of CH₄ conversion, but there was a slight decrease in CH₃Cl selectivity with about 64%. Despite the difference in acidity of HY zeolites having different Si/Al ratios, no prominent effect of the Si/Al ratios on the catalytic performance was observed. This suggests that the catalytic contribution of HY zeolites under the present reaction condition is not strong enough to overcome the spontaneous CH₄ chlorination. When the Pt/HY zeolite catalysts were used, the CH₄ conversion reached further up to 30% but the CH₃Cl selectivity decreased to 60%. Such an enhancement of CH₄ conversion could be attributed to the strong catalytic activity of HY and Pt/HY zeolite catalysts. However, both catalysts induced the radical cleavage of Cl₂ more favorably, which ultimately decreased the CH₃Cl selectivity. Such trade-off relationship between CH₄ conversion and CH₃Cl selectivity can be slightly broken by using Pt/NaY zeolite catalyst that is known to possess Frustrated Lewis Pairs (FLP) that are very useful for ionic cleavage of H₂ to H⁺ and H⁻. Similarly, in the present work, Pt/NaY(FLP) catalysts enhanced the CH₄ conversion while keeping the CH₃Cl selectivity as compared to the Pt/HY zeolite catalysts.     

C−C Bond Formation in Syngas Conversion over Zinc Sites Grafted on ZSM‐5 Zeolite

Despite significant progress achieved in Fischer–Tropsch synthesis (FTS) technology, control of product selectivity remains a challenge in syngas conversion. Herein, we demonstrate that Zn²⁺‐ion exchanged ZSM‐5 zeolite steers syngas conversion selectively to ethane with its selectivity reaching as high as 86 % among hydrocarbons (excluding CO₂) at 20 % CO conversion. NMR spectroscopy, X‐ray absorption spectroscopy, and X‐ray fluorescence indicate that this is likely attributed to the highly dispersed Zn sites grafted on ZSM‐5. Quasi‐in‐situ solid‐state NMR, obtained by quenching the reaction in liquid N₂, detects C₂ species such as acetyl (‐COCH₃) bonding with an oxygen, ethyl (‐CH₂CH₃) bonding with a Zn site, and epoxyethane molecules adsorbing on a Zn site and a Brønsted acid site of the catalyst, respectively. These species could provide insight into C?C bond formation during ethane formation. Interestingly, this selective reaction pathway toward ethane appears to be general because a series of other Zn²⁺‐ion exchanged aluminosilicate zeolites with different topologies (for example, SSZ‐13, MCM‐22, and ZSM‐12) all give ethane predominantly. By contrast, a physical mixture of ZnO‐ZSM‐5 favors formation of hydrocarbons beyond C₃₊. These results provide an important guide for tuning the product selectivity in syngas conversion.     

Identification of decomposition reactions for HMDSO organosilicon using quantum chemical calculations

Hexamethyldisiloxane [HMDSO, (CH₃)₃-SiOSi-(CH₃)₃] is an important precursor for SiO₂ formation during flame-based silica material synthesis. As a result, HMDSO reactions in flame have been widely investigated experimentally, and many results have indicated that HMDSO decomposition reactions occur very early in this process. In this paper, quantum chemical calculations are performed to identify the initial decomposition of HMDSO and its subsequent reactions using the density functional theory at the level of B3LYP/6-311+G (d, p). Four reaction pathways—(a) Si O bond dissociation of HMDSO, (b) Si C bond dissociation of HMDSO, (c) dissociation and recombination of Si O and Si C bonds, and (d) elimination of a methane molecule from HMDSO—have been examined and identified. From the results, it is found that the barrier of 84.38 kcal/mol and Si O bond dissociation energy of 21.55 kcal/mol are required for the initial decomposition reaction of HMDSO in the first pathway, but the highest free energy barrier (100.69 kcal/mol) is found in the third reaction pathway. By comparing the free energy barriers and reaction rate constants, it is concluded that the most possible initial decomposition reaction of HMDSO is to eliminate the CH₃ radical by Si C bond dissociation.     

Darstellung und charakterisierung von verbindungen des typs (CH3)3ME(CF3)2 (M = Si,Ge, Sn; E = P,As)

Various preparative routes for the synthesis of (CH₃)₃SiP(CF₃)₂ are discussed. The most favourable method, reaction of (CH₃)₃MPH₂ with HE(CF₃)₂, provides a good yield of (CH₃)₃ME(CF₃)₂ compounds (M = Si, Ge, Sn; E = P, As). The reaction rate is dependent on M (Si < Ge <Sn) und E (P < As). The stability and reactivity of the (CH₃)₃ME(CF₃)₂ compounds are discussed. The new compounds were characterized by NMR and IR spectra and by cleavage reactions of the M-E bond. ¹H, ¹⁹F NMR and IR spectral data are reported.     

Back Cover: Illustrating the Fate of Methyl Radical in Photocatalytic Methane Oxidation over Ag−ZnO by in situ Synchrotron Radiation Photoionization Mass Spectrometry (Angew. Chem. Int. Ed. 32/2023)

Photocatalysis has emerged as an ideal method for the direct activation and conversion of methane under mild conditions. In this reaction, methyl radical (⋅CH₃) was deemed a key intermediate that affected the yields and selectivity of the products. However, direct observation of ⋅CH₃ and other intermediates is still challenging. Here, a rectangular photocatalytic reactor coupled with in situ synchrotron radiation photoionization mass spectrometry (SR-PIMS) was developed to detect reactive intermediates within several hundred microseconds during photocatalytic methane oxidation over Ag−ZnO. Gas phase ⋅CH₃ generated by photogenerated holes (O⁻) was directly observed, and its formation was demonstrated to be significantly enhanced by coadsorbed oxygen molecules. Methoxy radical (CH₃O⋅) and formaldehyde (HCHO) were confirmed to be key C1 intermediates in photocatalytic methane overoxidation to CO₂. The gas-phase self-coupling reaction of ⋅CH₃ contributes to the formation of ethane, which indicates the key role of ⋅CH₃ desorption in the highly selective synthesis of ethane. Based on the observed intermediates, the reaction network initiated from ⋅CH₃ of photocatalytic methane oxidation could be clearly illustrated, which is helpful for studying the photocatalytic methane conversion processes.     

New Strategy for the Synthesis of Diethylenetriaminetetraacetic Acid Functionalized Polysiloxane Ligand Systems

A new rout was used for the synthesis of porous solid polysiloxane matrix of the general formula P-(CH₂)₃N(CH₂COOEt)-(CH₂)₂N(CH₂COOEt)-(CH₂)₂-N(CH₂COOEt)₂ (where P represents [Si-O]_n) by the reaction of diethylenetriaminetrimethoxysilane with ethyl chloroacetate followed by polymerization with tetraethylorthosilicate via the sol gel process. The functionalized diethylenetriaminetetraacetic acid polysiloxane system (P-DETATA) was then obtained by acid hydrolysis of the diethylenetriaminetetraethylacetate functionalized polysiloxane(P-DETATAc). FTIR, ¹³C, ²⁹Si CP-MAS NMR and XPS methods were used for characterization of their chemical structure. The new functionalized ligand system exhibits high capacity to coordinate with divalent metal ions (Co²⁺, Ni²⁺, and Cu²⁺) than its analogous ligand obtained by postmodification of triamine polysiloxane with ethyl chloroacetate.     

Thermal behavior of some compounds of methanesulfonic acid with transition metals

The following compounds of methanesulfonic acid, CH₃SO₃H, have been prepared: Cu(CH₃SO₃)₂ · 4 H₂O; Zn(CH₃SO₃)₂ · 4 H₂O; Mn(CH₃SO₃)₂ · 2 H₂O; Cd(CH₃SO₃)₂ · 2 H₂O and Ag(CH₃SO₃). Their thermal behavior has been studied using TG and DTA, together with X-ray analysis of the solid products formed during the heating. The water of hydration is evolved in one step (Mn, Cd) or in two step (Cu, Zn). The intermediate hydrates and the anhydrous salts are crystallized. The anhydrous Zn, Ag and Cd compounds melt, the anhydrous Cd salt undergoing a polymorphic transition before melting. They then begin to decompose in the temperature range 325–440°C. Under an inert atmosphere, the decomposition yields well-crystallized residues of various composition: Cu + Cu₂S; Ag + Ag₂S (the sulfides being in very minute amounts); MnS; CdS; ZnO + ZnS.     

Macrocyclic Polysiloxane Immobilized Ligand System and Its Structural Characterization

A new porous solid macrocyclic 1,4,7,10,14,17,20‐heptaazadocosane‐3,21‐dione polysiloxane ligand system of the general formula P‐(CH₂)₃‐C₁₅H₃₂O₂N₅, (where P represents [Si‐O]n siloxane network) has been prepared by the reaction of immobilized iminobis(N‐diethylenediamineacetamide)polysiloxane with 1,3 dibromopropane. The new macrocyclic polysiloxane ligand system exhibits high potential for the uptake of metal ions (Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺). Complexation with copper ions exhibits a high selectivity in which two copper ions were involved per one macrocyclic ligand group.     

Silicium-stickstoff-fluorverbidungen: V. Darstellung neuer silylaminofluorsilane

Compounds of the composition RR′SiFNR″Si(CH₃)₃ (R = H, F, CH₃, C₂H₅, C₃H₇, C₂H₃, C₆H₅, C(CH₃)₃; R = F, CH₃, C₆H₅; R″ = CH₃, C(CH₃)₃, Si(CH₃)₃) are obtained by the reaction of silicontetrafluoride or organo-substituted silicon-fluorides with the lithium salts of alkylsilylamines in a molar ratio of $\text{1}\text{1}$. The disubstituted compounds RSiF(NR′Si(CH₃)₃)₂ (R = H, F, CH₃, C₂H₃, C₆H₅; R′ = CH₃, C(CH₃)₃) result when the reactants are in a $\text{1}\text{2}$ molar-ratio. Likewise the unsymmetrical siliconfluorsilylamines of the formulae F₂Si(NRSi(CH₃)₃) (NR′Si(CH₃)₃) (R = CH₃, R′ = C(CH₃)₃), as well as the trisubstituted compounds FSi(NCH₃Si(CH₃)₃)₃ and FSi(NCH₃Si(CH₃)₃)₂(N(Si(CH₃)₃)₂) were made. By reacting phenyltrifluorsilane with dialkylamines ($\text{1}\text{2}$) C₆H₅SiF₂NR₂(R = CH₃, C₂H₅) was obtained. The IR-, mass-, ¹H and ¹⁹F NMR spectra of the above-mentioned compounds are reported.     

Elucidating the structures of isomeric silylenium ions (SiC3H 9 + , SiC4H 11 + , SiC5H 13 + ) by using specific ion/molecule reactions

Specific ion/molecule reactions are demonstrated that distinguish the structures of the following isomeric organosilylenium ions: Si(CH₃) ₃ ⁺ and SiH(CH₃)(C₂H₅)⁺; Si(CH₃)₂(C₂H₅)⁺ and SiH(C₂H₅) ₂ ⁺ ; and Si(CH₃)₂(i?C₃H₇)⁺, Si(CH₃)₂(n?C₃H₇)⁺, Si(CH₃)(C₂H₅) ₂ ⁺ , and Si(CH₃)₃(π?C₂H₄)⁺. Both methanol and isotopically labeled ethene yield structure-specific reactions with these ions. Methanol reacts with alkylsilylenium ions by competitive elimination of a corresponding alkane or dehydrogenation and yields a methoxysilylenium ion. Isotopically labeled ethene reacts specifically with alkylsilylenium ions containing a two-carbon or larger alkyl substituent by displacement of the corresponding olefin and yields an ethylsilylenium ion. Methanol reactions were found to be efficient for all systems, whereas isotopically labeled ethene reaction efficiencies were quite variable, with dialkylsilylenium ions reacting rapidly and trialkylsilylenium ions reacting much more slowly. Mechanisms for these reactions and differences in the kinetics are discussed.     

Complex formation involving Hg<Superscript>2+</Superscript> ions on the surface of the polysiloxane xerogels functionalized by 3-mercaptopropyl groups

The influence of parameters of the porous structure and the surface layer composition of the xerogels containing 3-marcaptopropyl and alkyl groups on their sorption properties toward the Hg²⁺ ions and the stability constants of the formed complexes, which are calculated using the model of chemical reactions, is studied. An increase in the overall surface concentration of the functional groups is shown to induce a change in the composition of the formed complexes. At the concentration of the functional groups lower than 0.01 mmol/m² the [HgS(CH₂)₃Si≡]⁺ complexes are formed, and above 0.01 mmol/m² the composition of the complexes depends on the mercury(II) content in the starting solution: at low contents the [Hg{S(CH₂)₃Si≡}₂] complexes are formed, whereas at higher concentrations the composition of the complexes becomes simpler. Only the [Hg{S(CH₂)₃Si≡}₂] complexes are formed on the nearly nonporous xerogel with the polymeric structure of the surface layer (the functional group concentration is 0.38 mmol/m²). This, in turn, leads to the situation that the maximum static sorption capacity (590–620 (mg of Hg²⁺)/(g of sorbent)) is observed for the xerogels with a rather low content of the 3-mercaptopropyl groups (3.0–3.8 mmol/g). The stability of the formed complexes also depends on the surface concentration of the functional groups: the stability constant of the 1: 1 Hg(II) complexes decreases with an increase in the concentration of thiol groups. The introduction of alkyl groups into the surface layer also decreases the stability of the complexes formed. The [Hg{S(CH₂)₃Si≡}₂] complexes formed in the surface layer of the xerogels are characterized by similar stability constants.     

Über Reaktionen des P4S10 mit siliciumorganischen Verbindungen

Reactions of P₄S₁₀ with Organosilicon Compounds P₄S₁₀ ( 1 ) can be degraded with silicon-nitrogen compounds. 1 reacts with (CH₃)₃Si? N(CH₃)₂ ( 2 a ) and (CH₃)₃Si? N(C₂H₅)₂ ( 2 b ) to yield S?P[N(CH₃)₂]₂SSi(CH₃)₃ ( 3 a ) and ( 3 b ). By the reaction of 1 with [(CH₃)₃Si]₂S ( 4 ) S?P[S? Si(CH₃)₃]₃ ( 6 ) is formed in high yield. (C₆H₅PS₂)₂ ( 7 ) was used as a model to investigate the course of the reaction. This leads to C₆H₅P(S)? [N(CH₃)₂]SSi(CH₃)₃ ( 9 ) and C₆H₅P(S)[SSi(CH₃)₃]₂ ( 10 ). The reaction mechanism will be discussed. The n.m.r. data and mass spectra are reported.