New Functional Alkoxysilanes and Silatranes: Synthesis, Structure, Properties, and Possible Applications

The aza-Michael reaction of 3-aminopropyltriethoxysilane (1) and -silatrane (2) with acrylates affords functionalized silyl-(3–8) and silatranyl-(9–14) mono- and diadducts with up to a 99% yield. Their structure has been proved with IR and NMR spectroscopies, mass spectrometry and XRD analysis. The hydrolytic homo-condensation of triethoxysilanes 3–5 gives siloxanes 3a–5a, which form complexes with Ag, Cu, and Ni salts. They are also able to adsorb these metals from solutions. The hetero-condensation reaction of silanes 4–8 with OH groups of zeolite (Z), silica gel (S) and glass (G) delivers the modified materials (Z4, S7, G4, G5, G7, G8, etc.), which can adsorb ions of noble metal (Au, Rh, Pd: G4 + Au, G5 + Pd, G7 + Rh). Thus, the synthesized Si-organic polymers and materials turned out to be promising sorbents (enterosorbents) of noble, heavy, toxic metal ions and can be applied in industry, environment, and medicine.


Introduction
Functional 1-organyltrialkoxysilanes, R-Si(OAlk)3, are well-known organosilicon compounds.They have found applications in materials science and various technologies as building blocks, hybrid-and nano-materials, optical sensors, solar cells, catalysts, silicone sealants, and adhesives.These materials are formed via the homo-condensation reaction to afford siloxanes or silsesquioxanes, [R-SiO1.5],(Scheme 1) [1][2][3][4].Such carbofunctional siloxanes are efficient ingredients of rubber mixtures for non-combustible, water-and wear-resistant tires, as well as for ion-exchange and complex-forming sorbents of heavy and noble metals.
Carbofunctional polyorganylsilsesquioxanes, like siloxanes, are also excellent sorbents.They are easily synthesized and their composition and properties can be readily reproduced.The spatially cross-linked silsesquioxane structure of these sorbents ensures their high thermal stability and resistance to highly aggressive acidic media.At the same substituents.An important application of carbofunctional polyorganylsilsequioxanes and initial organosilicon monomers is in the design of a new generation of "test systems".In economic terms, it is more rational to use inexpensive natural zeolites and silicas.However, such materials are not as efficient in the extraction of the target components, for example, noble metals.More expensive synthetic sorbents, primarily carbofunctional polyorganylsilsesquioxanes, due to a wide range of reactive groups that can be easily introduced into their composition, are characterized by higher efficiency and wider application scope [5,6].
Int. J. Mol.Sci.2023, 24, x FOR PEER REVIEW 2 of 15 time, the silsesquioxane matrix does not affect the specific reactivity of their carbofunctional substituents.An important application of carbofunctional polyorganylsilsequioxanes and initial organosilicon monomers is in the design of a new generation of "test systems".In economic terms, it is more rational to use inexpensive natural zeolites and silicas.However, such materials are not as efficient in the extraction of the target components, for example, noble metals.More expensive synthetic sorbents, primarily carbofunctional polyorganylsilsesquioxanes, due to a wide range of reactive groups that can be easily introduced into their composition, are characterized by higher efficiency and wider application scope [5,6].
In addition, functional 1-organyltrialkoxysilanes are employed in the modification (silanization) of hydroxylated surfaces (silicon oxide, alumina, quartz, mica, zeolite, glass, etc.) via hetero-condensation (grafting) to give self-assembled monolayers (SAMs) (Scheme 2).The interest in SAM is due to their potential application as functional modules with tailor-made physical and chemical properties.This is especially true for the use of SAM in surface engineering.For example, the advantages of unique properties and complex architecture of SAM are especially pronounced in analytical chemistry.An effective technology is one for the formation of a pattern on the surface of semiconductors.In addition, engineered surfaces can improve adhesion.Such surfaces (modified materials) can be used as heterogeneous catalysts, special filters/membranes, and, like functional siloxanes, as effective sorbents/enterosorbents of heavy or toxic metals [7,8].
All of the above is true both for 3-aminopropyltriethoxysilane, NH2-(CH2)3-Si(OCH2CH3)3 (1), and 3-aminopropylsilatrane, NH2-(CH2)3-Si(OCH2CH2)3N (2) (Scheme 3) [9,10].As seen from Scheme 3, compounds 1 and 2 are close analogues.However, it should be emphasized that silatranes (unlike silanes and siloxanes) possess high and diverse biological and pharmacological activity [11].For example, silatrane 2 and its derivatives exhibit a growth-stimulating effect on agricultural crops (wheat, rye, oats, corn, etc.)The interest in SAM is due to their potential application as functional modules with tailor-made physical and chemical properties.This is especially true for the use of SAM in surface engineering.For example, the advantages of unique properties and complex architecture of SAM are especially pronounced in analytical chemistry.An effective technology is one for the formation of a pattern on the surface of semiconductors.In addition, engineered surfaces can improve adhesion.Such surfaces (modified materials) can be used as heterogeneous catalysts, special filters/membranes, and, like functional siloxanes, as effective sorbents/enterosorbents of heavy or toxic metals [7,8].
All of the above is true both for 3-aminopropyltriethoxysilane, NH 2 -(CH 2 ) 3 -Si(OCH 2 CH 3 ) 3 (1), and 3-aminopropylsilatrane, NH 2 -(CH 2 ) 3 -Si(OCH 2 CH 2 ) 3 N (2) (Scheme 3) [9,10].time, the silsesquioxane matrix does not affect the specific reactivity of their carbofunctional substituents.An important application of carbofunctional polyorganylsilsequioxanes and initial organosilicon monomers is in the design of a new generation of "test systems".In economic terms, it is more rational to use inexpensive natural zeolites and silicas.However, such materials are not as efficient in the extraction of the target components, for example, noble metals.More expensive synthetic sorbents, primarily carbofunctional polyorganylsilsesquioxanes, due to a wide range of reactive groups that can be easily introduced into their composition, are characterized by higher efficiency and wider application scope [5,6].
In addition, functional 1-organyltrialkoxysilanes are employed in the modification (silanization) of hydroxylated surfaces (silicon oxide, alumina, quartz, mica, zeolite, glass, etc.) via hetero-condensation (grafting) to give self-assembled monolayers (SAMs) (Scheme 2).The interest in SAM is due to their potential application as functional modules with tailor-made physical and chemical properties.This is especially true for the use of SAM in surface engineering.For example, the advantages of unique properties and complex architecture of SAM are especially pronounced in analytical chemistry.An effective technology is one for the formation of a pattern on the surface of semiconductors.In addition, engineered surfaces can improve adhesion.Such surfaces (modified materials) can be used as heterogeneous catalysts, special filters/membranes, and, like functional siloxanes, as effective sorbents/enterosorbents of heavy or toxic metals [7,8].
Among nucleophilic addition processes, the aza-Michael reaction holds a special place [22][23][24].This general reaction proceeds with the participation of various Michael donors (carbamates, amides, amines) and Michael acceptors (unsaturated nitriles, sulfones, phosphonates, and also acrylates).Acrylates and acrylate polymers are known to be functional compounds and materials.The latter have valuable characteristics such as low cost, transparency, thermoplasticity, stability, biocompatibility, and high adhesion to metals [25].In particular, methacrylate-functionalized silanes and silatranes are used to produce hybrid materials and in sol-gel processes and coating technologies [26,27].
The amino group, which is contained in compounds 1 and 2, makes them functional and allows them to be involved into the aza-Michael reaction.It was reported that some aminoalkoxysilanes can be added via the aza-Michael process [28,29].However, to the best of our knowledge, the participation of 3-aminopropylsilatrane 2 in this reaction was described only in one work [30] on the example of addition to N-phenylmaleimide.
In order to expand the scope of polyfunctional Si-organic compounds and materials, here we have implemented the aza-Michael reaction of silane 1 and silatrane 2 with various acrylates and have studied the adsorption activity of the target adducts and their derivatives.
Among nucleophilic addition processes, the aza-Michael reaction holds a special place [22][23][24].This general reaction proceeds with the participation of various Michael donors (carbamates, amides, amines) and Michael acceptors (unsaturated nitriles, sulfones, phosphonates, and also acrylates).Acrylates and acrylate polymers are known to be functional compounds and materials.The latter have valuable characteristics such as low cost, transparency, thermoplasticity, stability, biocompatibility, and high adhesion to metals [25].In particular, methacrylate-functionalized silanes and silatranes are used to produce hybrid materials and in sol-gel processes and coating technologies [26,27].
The amino group, which is contained in compounds 1 and 2, makes them functional and allows them to be involved into the aza-Michael reaction.It was reported that some aminoalkoxysilanes can be added via the aza-Michael process [28,29].However, to the best of our knowledge, the participation of 3-aminopropylsilatrane 2 in this reaction was described only in one work [30] on the example of addition to N-phenylmaleimide.
In order to expand the scope of polyfunctional Si-organic compounds and materials, here we have implemented the aza-Michael reaction of silane 1 and silatrane 2 with various acrylates and have studied the adsorption activity of the target adducts and their derivatives.
Among nucleophilic addition processes, the aza-Michael reaction holds a special place [22][23][24].This general reaction proceeds with the participation of various Michael donors (carbamates, amides, amines) and Michael acceptors (unsaturated nitriles, sulfones, phosphonates, and also acrylates).Acrylates and acrylate polymers are known to be functional compounds and materials.The latter have valuable characteristics such as low cost, transparency, thermoplasticity, stability, biocompatibility, and high adhesion to metals [25].In particular, methacrylate-functionalized silanes and silatranes are used to produce hybrid materials and in sol-gel processes and coating technologies [26,27].
The amino group, which is contained in compounds 1 and 2, makes them functional and allows them to be involved into the aza-Michael reaction.It was reported that some aminoalkoxysilanes can be added via the aza-Michael process [28,29].However, to the best of our knowledge, the participation of 3-aminopropylsilatrane 2 in this reaction was described only in one work [30] on the example of addition to N-phenylmaleimide.
In order to expand the scope of polyfunctional Si-organic compounds and materials, here we have implemented the aza-Michael reaction of silane 1 and silatrane 2 with various acrylates and have studied the adsorption activity of the target adducts and their derivatives.

Spectroscopic and Spectrometric Studies
The composition and structure of the obtained compounds were confirmed with IR, NMR spectroscopy, mass spectrometry and elemental and X-ray diffraction analysis (see Section 3 and Supplementary Materials).
The 1 H NMR spectra showed the characteristic triplets and quartets of the triethoxysilyl groups (CH 3 and OCH 2 ) in the regions of 0.5-06 ppm and 1.15-l.20 ppm (J = 7.0 Hz), respectively.The 1 H NMR spectra contained the characteristic triplets of the silatranyl moiety representing the NCH 2 and OCH 2 groups at 2.73-2.79ppm and 3.69-3.76ppm (J = 5.9 Hz), respectively.The spectra of all compounds exhibited multiplets of the SiCH 2 , CH 2 , and NCH 2 groups of propyl moiety at 0.30-0.41ppm, 1.46-1.61ppm and 2.41-2.52ppm, respectively.In the spectra of all compounds, multiplets of the CH 2 , and CH 2 N groups of ethyl moiety were observed at 2.47-2.52ppm and 2.84-2.90ppm, respectively.
In the 13  The 29 Si NMR spectra of all silatranes contained peaks of the silatranyl moiety at ∼−85 ppm.Such δ values indicate an intramolecular transannular Si ← N dative bond [15,18].

Mass Spectrometry
We failed to record high resolution mass spectra of silanes 3-8, possibly due to their hydrolytic instability.However, the spectra of silatranes confirmed their composition and structure.For example, the mass spectrum of compound 9 contained the main peak in the form of the [M + H] + ion.The theoretical m/z value was 286.158695; in reality, a value of 286.15876 was obtained, so the error was 0.2 ppm.The mass spectrum of silatrane 12 was registered in the form of the ion [M + H] + with m/z 339.18498 (theoretical m/z value was 339.185244); the error was 0.8 ppm.

X-ray Spectrometry
The structure of compound 9 was proved with X-ray diffraction analysis.Single crystals of 9 were grown from CHCl 3 solution.The molecular structure is depicted in Figure 1.339.185244); the error was 0.8 ppm.

X-ray Spectrometry
The structure of compound 9 was proved with X-ray diffraction analysis.Single crystals of 9 were grown from CHCl3 solution.The molecular structure is depicted in Figure 1.Compounds 3-5 and 3a-5a were preliminary studied as chelating ligands and potential sorbents of noble (AgI) and transition Cu(II) and Ni(II) metals.Monomers 3-5 turned out to be inefficient owing to their low stability.At the same time, extremely stable polymers 3a-5a showed high activity (static sorption capacity, SSC = 138-289 mg/g), see, for example, Figure 2 and the Supplementary Materials (compare with SSC 29.5 mg/g, 24.9 mg/g and 16.6 mg/g for Cu(II), Co(II) and Ni(II), respectively [8]).Atomic coordinates, bond lengths, bond angles and atomic displacement parameters for the crystal structure of 9 have been deposited with the Cambridge Crystallographic Data Centre (CCDC) with the deposition number CCDC 2263862.These data can be obtained free of charge from the CCDC via https://www.ccdc.cam.ac.uk/structures/ (accessed on 18 May 2023).
registered in the form of the ion [M + H] + with m/z 339.18498 (theoretical m/z value was 339.185244); the error was 0.8 ppm.

X-ray Spectrometry
The structure of compound 9 was proved with X-ray diffraction analysis.Single crystals of 9 were grown from CHCl3 solution.The molecular structure is depicted in Figure 1.
Compounds 3-5 and 3a-5a were preliminary studied as chelating ligands and potential sorbents of noble (AgI) and transition Cu(II) and Ni(II) metals.Monomers 3-5 turned out to be inefficient owing to their low stability.At the same time, extremely stable polymers 3a-5a showed high activity (static sorption capacity, SSC = 138-289 mg/g), see, for example, Figure 2 and the Supplementary Materials (compare with SSC 29.5 mg/g, 24.9 mg/g and 16.6 mg/g for Cu(II), Co(II) and Ni(II), respectively [8]).The sorption equilibrium with respect to silver was reached for 20 min.For nickel and copper, this takes 30 min.Kinetic dependences were represented by typical curves, which had a steep section in the region of 10-30 min of the sorbate solution contact with the polymer; see, for example, Figure 3.The sorption equilibrium with respect to silver was reached for 20 min.For nickel and copper, this takes 30 min.Kinetic dependences were represented by typical curves, which had a steep section in the region of 10-30 min of the sorbate solution contact with the polymer; see, for example, Figure 3.The sorption equilibrium with respect to silver was reached for 20 min.For nickel and copper, this takes 30 min.Kinetic dependences were represented by typical curves, which had a steep section in the region of 10-30 min of the sorbate solution contact with the polymer; see, for example, Figure 3.The C≡N-Ag coordination was confirmed by IR spectroscopy.For instance, the IR spectrum of the initial powder 3a showed the absorption peak at 2236 cm -1 , which corresponded to C≡N stretching vibrations.In the case of 3b with the additive of AgNO3, the Mechanistically, the sorption likely occurs via the formation of carbonyl and nitrile complexes with Ag, Cu and Ni salts (for example, complex 3b, Scheme 7).The sorption equilibrium with respect to silver was reached for 20 min.For nickel and copper, this takes 30 min.Kinetic dependences were represented by typical curves, which had a steep section in the region of 10-30 min of the sorbate solution contact with the polymer; see, for example, Figure 3.The C≡N-Ag coordination was confirmed by IR spectroscopy.For instance, the IR spectrum of the initial powder 3a showed the absorption peak at 2236 cm -1 , which corresponded to C≡N stretching vibrations.In the case of 3b with the additive of AgNO3, the The C≡N-Ag coordination was confirmed by IR spectroscopy.For instance, the IR spectrum of the initial powder 3a showed the absorption peak at 2236 cm −1 , which corresponded to C≡N stretching vibrations.In the case of 3b with the additive of AgNO 3 , the absorption peak shifted and appeared at 2257 cm −1 (∆ν = 21 cm −1 ).This indicates that the C≡N group of polymer 3b interacted with the Ag + ion.The IR spectrum of the starting methylacrylate silsesquioxane, MeO(O)C(CH 2 ) 2 NH-(CH 2 ) 3 -Si(O 1.5 ) 3 4a, contained a band at 1700 cm −1 , which was assigned to the stretching vibration of the C=O bond.IR spectra 4b showed clear shifts in the C=O stretching vibration to 1690 cm −1 and 1681 cm −1 , ∆ν = 10 cm −1 and 19 cm −1 , respectively, after the addition of NiCl 2 and CuCl 2 .
The analysis of our own data and those from the literature demonstrates that the interaction of metal ions (Ag, Cu, Ni) with C≡N and C=O functional groups of polyorganosilsesquioxanes 3a-5a is thermodynamically favorable [34].It occurs via chelate interaction and is accompanied by the formation of 2:1 complexes (for example, Scheme 7) [35,36].
Thus, polymers 3a-5a are prospective chemically and thermally stable sorbents (enterosorbents) of heavy and toxic metal ions and can be used in industry, the environment and medicine.

Modification of Hydroxylated Surfaces' (Zeolite, Silicagel, Glass) Sorption
Functionalized materials find wide applications in the fields of catalysis, separation, sensors, optoelectronics, environmental technology, and biomedical applications due to their high specific surface area and chemical, thermal and mechanical stability [7,8].
The high density of OH groups, for example, on the silica surfaces, promotes the covalent grafting of useful functional groups onto the interior and exterior surfaces via hetero-condensation reactions (see Scheme 2).Functional 1-organyltrialkoxysilanes are very often used to modify hydroxylated surfaces.The organic-inorganic skeletons thus obtained can exhibit significant hydrophobicity, high adsorption activity, and selectivity compared to the starting materials [9,10].
Using the synthesized 1-organyltrialkoxysilanes 4-8 containing C≡N, C=O, NH and H 2 N groups, a series of preliminary experiments on the modification (silanization) of zeolite (Z), silica gel (S) and glass (G) surfaces was carried out.The degree of modification of zeolite "heulandite" Z with silane 4 was estimated from the increase in the mass of modified zeolite (Z4).The content of the modifier in Z increased linearly at higher concentrations of silane 4 solution (Table 1).The SEM-EDX analysis was performed to confirm the fixation of modifier 4 on the surface of the zeolite Z. SEM images of Z and Z4 are shown in Figure 4.The surface morphology of natural zeolites, including heulandite Z, is rather het ogeneous due to the coexistence of various crystalline phases (Figure 4a).The chemi modification of Z changes the surface structure of the material (Figure 4b).After mod cation, the surface of Z becomes more uniform and less porous.This indicates a hi degree of the zeolite coating with the modifier layer.
The high degree of Z coating with modifier 4 was also confirmed by the EDX ana sis (Figures 5 and 6).The increased carbon (31 wt.% vs. 5 wt.%) and nitrogen (11 wt.% 0 wt.%) content, and the practical absence of aluminum and sodium on the Z4 surfa indicate that the zeolite surface in the studied area was covered with a layer of 4. The surface morphology of natural zeolites, including heulandite Z, is rather heterogeneous due to the coexistence of various crystalline phases (Figure 4a).The chemical modification of Z changes the surface structure of the material (Figure 4b).After modification, the surface of Z becomes more uniform and less porous.This indicates a high degree of the zeolite coating with the modifier layer.
The high degree of Z coating with modifier 4 was also confirmed by the EDX analysis (Figures 5 and 6).The increased carbon (31 wt.% vs. 5 wt.%) and nitrogen (11 wt.% vs. 0 wt.%) content, and the practical absence of aluminum and sodium on the Z4 surface, indicate that the zeolite surface in the studied area was covered with a layer of 4. modification of Z changes the surface structure of the material (Figure 4b).After modification, the surface of Z becomes more uniform and less porous.This indicates a high degree of the zeolite coating with the modifier layer.
The high degree of Z coating with modifier 4 was also confirmed by the EDX analysis (Figures 5 and 6).The increased carbon (31 wt.% vs. 5 wt.%) and nitrogen (11 wt.% vs. 0 wt.%) content, and the practical absence of aluminum and sodium on the Z4 surface, indicate that the zeolite surface in the studied area was covered with a layer of 4.   A similar picture was observed when silica gel (S) and glass (G) were treated with silanes 7 and 4. Modified surfaces S7 and G4 were formed, respectively.
The hetero-condensation reaction (Scheme 2) allowed the surfaces of zeolite, silica gel and glass modified with functional silanes (C≡N, C=O, NH and NH2 groups) to be obtained.According to Pearson's hard and soft acid-base theory, compounds (polymers) containing functional groups with N or O donor atoms should be prospective sorbents of precious metal ions.Precious metals are widely used in many fields, e.g., in the electrical and electronics industry, various chemical processes, the manufacture of catalysts and the production of corrosion resistant materials and jewelry.
Therefore, model samples of glass modified with functional silanes were used for a preliminary evaluation of the noble metals' sorption from aqueous solutions of AuCl3, A similar picture was observed when silica gel (S) and glass (G) were treated with silanes 7 and 4. Modified surfaces S7 and G4 were formed, respectively.
The hetero-condensation reaction (Scheme 2) allowed the surfaces of zeolite, silica gel and glass modified with functional silanes (C≡N, C=O, NH and NH 2 groups) to be obtained.According to Pearson's hard and soft acid-base theory, compounds (polymers) containing functional groups with N or O donor atoms should be prospective sorbents of precious metal ions.Precious metals are widely used in many fields, e.g., in the electrical and electronics industry, various chemical processes, the manufacture of catalysts and the production of corrosion resistant materials and jewelry.
Therefore, model samples of glass modified with functional silanes were used for a preliminary evaluation of the noble metals' sorption from aqueous solutions of AuCl 3 , RhCl 3 and PdCl 2 .The sorption solutions have equal concentrations of each metal 5 mg/25 mL (square of glass 1 cm 2 , contact time 4 h, pH = 2-5, temperature 25 • C).After sorption from solutions, samples of modified glasses (G4, G5, G7 and G8) were isolated, washed (ethanol, water) and dried (100 • C, 4 h).The EDX analysis of these samples enabled an estimation of the degree of metal ions retained by these glasses from solutions.
EDX spectra and the mapping of metals on the surfaces of G4, G5, G7 and G8 (+Au, +Pd, +Rh) are shown in Figures 7 and 8 and Figures S26-S34.
The samples contained Au 11-15 wt.%, Pd 6-14 wt.% and Rh 0.8-6 wt.% (Figure 7 and Figures S26-S34).The content can be compared with Cu 2.28 wt.%, Co 2.13 wt.% and Ni 0.95 wt.% [8].This indicates that the modified glasses are good sorbents for the extraction of these metals.Moreover, glasses coated with monosilanes (G4 and G5) showed the best results.Metal adsorption increased in the series Rh < Pd < Au and did not change at pH = 2, 3 and 5.
The adsorption of Au(III), Rh(III) and Pd(II) may be due to the ionic mechanism of the interaction between protonated nitrogen atoms in G4, G5, G7 and G8 and chloranionic metal complexes, or due to the formation of chelate compounds of metal ions with donor N or O atoms.Both mechanisms are assumed to be probable [37].
Thus, we have demonstrated that the new sorbents have a high potential for the analysis and concentration of Au(III), Rh(III) and Pd(II).The procedure earlier described was used to immobilize silanes on the zeolite (Z) surface [38].Syntheses of silane-functionalized silica gel (S) and glass (G) were described in [39,40], respectively.Reagents of high or analytical purity were used for all sorption experiments.The 1 mg mL −1 Au(III), Rh(III) and Pd(II) standard stock solutions were prepared by dissolving pure HAuCl 4 •4H 2 O, RhCl 3 •3H 2 O and PdCl 2 in dilute HCl, respectively [37].

Methods
The IR spectra were registered on a Varian 3100 FTIR spectrometer (Digilab LLC, Marlborough, MA, USA) in 4000-400 cm −1 range with the sample as a thin film or tablet (KBr).
Mass spectra were recorded on an HR-TOF-ESI-MS Agilent 6210 with the registration mode of positive ions with acetonitrile as a solvent (in case of poor solubility by ultrasound) and 0.1% perfluorobutyric acid as an ionizing agent.
X-ray Diffraction Analysis.The single crystals of compounds 6 and 12 were grown by the slow evaporation of chloroform solutions at room temperature.The X-ray diffraction data were collected with a Bruker D8 VENTURE diffractometer (Bruker Optik GmbH, Ettlingen, Germany) (PHOTON III CMOS detector, Mo IµS3.0 X-ray source, Montel mirrorfocused MoKα radiation λ = 0.71073 Å, N 2 -flow cryostat) via 0.5 • ωand ϕ-scan techniques.Data were corrected for absorption effects using the multi-scan method (SADABS) [41].The structure was solved and refined using the Bruker SHELXTL Software Package [42].
Elemental analysis was performed on a Thermo Scientific Flash 2000 Elemental Analyzer (Thermo Fisher Scientific Inc., Milan, Italy).Melting points were determined on a Kofler Hot-Stage Microscope PolyTherm A apparatus (Wagner & Munz GmbH, München, Germany).
The spectrophotometric determination of the elements was carried out on Specol-10 spectrophotometers and a KFK-2 photocolorimeter using appropriate techniques [43].
The morphology of the surfaces was determined with scanning electron microscopy using a Hitachi TM3000 electron microscope (Hitachi High-Technologies Corporation, Tokyo, Japan) with a magnification up to 30,000× and a resolution up to 25 nm.The experiments were performed at 5 kV.Surface elements were established by analysis of energy-dispersive X-ray spectra (EDX) (Quantax 70).The samples were scanned on a Quanta 200 FEI SEM-EXD electron microscope (Quanta 200 FEI, Hillsboro, OR, USA).

Chemistry
General Procedure for the Synthesis of 3-14.A mixture of silane 1 or silatrane 2 (1 mmol) and the corresponding acrylate (1 or 2 mmol) in 10 mL of methanol was stirred at 50 • C for 2-4 h under an inert atmosphere (N 2 ) or in air.The solvent was removed under reduced pressure.The residue was washed many times with ether and dried to give products 3-14.
In addition, the synthesized silanes 4-8 were employed for the modification (silanization) of surfaces of zeolite (Z), silica gel (S), and glass (G) surfaces to produce modified materials: Z4, S7, G4, G5, G7, G8, etc.The latter were used to study the sorption of noble metals (AuCl 3 , RhCl 3 , PdCl 2 ).EDX spectra and the mapping of metals proved the formation of layers G4 + Au, G5 + Pd, G7 + Rh and others.The sorption of metals increased in the series Rh < Pd < Au.The samples contained Au (up to 15%), Pd (up to 14%) and Rh (up to 6%).Thus, synthesized Si-organic polymers and materials are promising chemically and thermally stable sorbents (enterosorbents) of noble, heavy, toxic metal ions and can be used in industry, the environment and medicine.

9 Figure 1 .
Figure 1.Molecular structure of compound 9. Atomic coordinates, bond lengths, bond angles and atomic displacement parameters for the crystal structure of 9 have been deposited with the Cambridge Crystallographic Data Centre (CCDC) with the deposition number CCDC 2263862.These data can be obtained free of charge from the CCDC via https://www.ccdc.cam.ac.uk/structures/ (accessed on 18 May 2023).

Figure 3 .Scheme 7 .
Figure 3.The effect of time on the degree of sorption of metals by polysiloxane 3a.Mechanistically, the sorption likely occurs via the formation of carbonyl and nitrile complexes with Ag, Cu and Ni salts (for example, complex 3b, Scheme 7).

Figure 3 .
Figure 3.The effect of time on the degree of sorption of metals by polysiloxane 3a.

Figure 3 .Scheme 7 .
Figure 3.The effect of time on the degree of sorption of metals by polysiloxane 3a.Mechanistically, the sorption likely occurs via the formation of carbonyl and nitrile complexes with Ag, Cu and Ni salts (for example, complex 3b, Scheme 7).

Figure 5 .
Figure 5. EDX spectrum and elemental composition of the initial Z.

Figure 5 .
Figure 5. EDX spectrum and elemental composition of the initial Z.Int.J. Mol.Sci.2023, 24, x FOR PEER REVIEW 9 of 15

Figure 6 .
Figure 6.EDX spectrum and elemental composition of modified zeolite Z4.

Figure 6 .
Figure 6.EDX spectrum and elemental composition of modified zeolite Z4.

Table 1 .
Degree of Z modification with silane 4 (initial weight of Z 10 g, solvent: hexane).