Si Bond Research Articles

Synthesis of Phosphine-Functionalized Silicon Cubane and Its Oxidative Addition, Giving a Bis(silyl)copper Complex

A new strategy for the introduction of a second type of Si atom to silicon cubanes has been developed starting from the tricyclic hexasilane dianion [Ar6Si6]2- (Ar = 2,4,6-Me3C6H2). Treatment of the dianion with Ar'SiCl3, followed by KC8, gave new types of octasilacubanes Ar6Ar'2Si8 [Ar' = 2,4,6-iPr2C6H2 (3a), 2-Ph2PC6H4 (3b)] in high yields. Remarkably, treatment of cubane 3b bearing with two phosphine groups with 2 equiv of CuCl in CH2Cl2 yielded the bis(silyl)copper complex via the selective oxidative addition of the newly formed Si-Si bond to Cu ion. Single-crystal X-ray analysis indicated the unique square-planar, four-coordinate Cu cation paired with the [CuCl2]- counteranion.

Performance and mechanisms of PropS-SH/Ce(dbp)3 coatings in the inhibition of pyrite oxidationtion for acid mine drainage control

Inhibition of tailings oxidation could availably control the generation of acid mine wastewater from its source. Organosilanes serving as a high-efficiency inhibitor of the oxidation of pyrite, bring some problems including safety hazards caused by large amounts of organic solvents, difficult high-temperature curing, poor long-term properties, and so on. In our work, the PropS-SH/Ce (dbp)3 (PS/Ce (dbp)3) passivator with excellent passivation performance and self-healing properties was prepared by choosing 3-mercaptopropyltrimethoxysilane (PropS-SH) and dibutyl phosphate (Ce (dbp)3) as the main passivating agent and the repair agent, respectively. We reduced the ratio of ethanol to water by adjusting the pH of the organosilane condensation and also achieved room-temperature curing by extending the curing time. Electrochemical and chemical leaching experiments results showed that the most appropriate addition of Ce (dbp)3 was 0.2 wt% for enhancing the passivation performance of the passivated coating. In a 6-month chemical leaching experiment, the PS/Ce (dbp)3-0.2 passivation coating cured at room temperature showed a better passivation effect and maintained 90.55% and 78.54% of total Fe and SO42− passivation efficiencies. The passivation and self-healing mechanisms were investigated by FT-IR, XPS, 29Si NMR, and other characterization methods, which were as follows: silane formed a cross-linked mesh structure by Si–O–Si bonding, in which Ce (dbp)3 was physically filled. And the Si–OH on the surface of the passivation film formed Fe–O–Si bonds with the hydroxyl groups on the surface of the pyrite, thus attaching to the surface of the pyrite and isolating the oxidation medium. When the passivation coating was locally damaged, the oxidation reaction caused a change in pH, which accelerated the dissolution of Ce (dbp)3 in the passivation layer. Ce3+ underwent a valence change and formed a CeO2 precipitate, while dbp− could form a complex with Fe2+ on the pyrite surface, both of which worked together to repair the broken passivation coating and prevent the oxidation reaction.

Molecularly imprinted ormosil as a sorbent for targeted dispersive solid phase micro extraction of pyriproxyfen from strawberry samples

Novel molecularly imprinted organically modified silica was prepared by reacting acrylamide and 3-(tri-methoxysilyl) propyl methacrylate followed by condensation and hydrolysis with tetraethyl ortho-silicate for the determination of pyriproxyfen. The sorbent proved to be highly selective for the template molecule, pyriproxyfen. The characterization of sorbent was carried out using SEM, BET and TGA. The prominent peaks in FTIR at 3700 cm−1 and 1071 cm−1 confirmed the stretching of amide group's N–H and Si–O–Si bond linkage of MIOrmosil. The pseudo-first-order model (R2 0.99) described the adsorption kinetics of the MIOrmosil, whereas among adsorption isotherms, Freundlich model showed the best fit (R2 0.99). The molecularly imprinted silica was applied for the determination of target analytes from strawberries sample using dispersive solid-phase micro extraction (DSPME) followed by high-performance liquid chromatography (HPLC). The LOD (4.93 x10−5 μg mL−1) and LOQ (1.49 x10−4 μg m-1) values were calculated by signal to noise ratio through HPLC. Results show that the maximum binding capacity and percentage recovery values of MIOrmosil were 13 mg g−1 (n = 5) and 97.3% respectively.

Hybrid Bicyclo[1.1.0]butanes [(R4Si3)CH2] and [(R4Si2Ge)CH2] (R = SiMetBu2): Synthesis and Thermal Isomerization to Alkyl-Substituted Cyclopropenes [R3Si3]CH2R and [R3Si2Ge]CH2R

Hybrid bicyclo[1.1.0]butanes comprised of different group 14 elements, namely, 1,2,3-trisilabicyclo[1.1.0]butane and 1,3-disila-2-germabicyclo[1.1.0]butane, were readily prepared by the reductive dichlorination of 1,3-dichlorocyclobutane precursors. Both compounds feature exceptionally short bridging Si–Si bonds and practically planar geometry around the bridging Si atoms, thus representing a novel structural motif in the chemistry of the heavy analogues of bicyclo[1.1.0]butanes. These peculiar structures were explained by the steric interaction between the substituents at the bridging and bridgehead positions. Thermolysis of the title bicyclo[1.1.0]butanes in toluene at 130 °C resulted in their isomerization to the alkyl-substituted cyclopropene analogues. The mechanism of this isomerization was revealed in detail on the basis of deuterium-labeled experiments, kinetic investigations, trapping experiments, and computational studies to establish the nature of the key intermediate of the whole isomerization process.

Visible Light Thiyl Radical-Mediated Desilylation of Arylsilanes.

A straightforward, visible-light triggered desilylation of arylsilanes by thiyl radicals is presented. Silyl groups are often used to block a reactive position in multi-step organic synthesis, for which a mild cleavage at a late-stage will provide new possibilities and disconnection routes by CAr -Si cleavage/deprotection. In this work, commercially available and cheap disulfides are employed for the first time in this type of C(sp2 )-Si bond cleavage reactions. Thus, upon irradiation with visible-light, homolytic cleavage of the disulfide give rise to the corresponding thiyl radical that allows for a radical chain mechanism. This methodology represents a mild, fast and simple approach suitable for a broad variety of simply substituted arylsilanes. Moreover, the procedure could be easily extended to natural products and therapeutic derivatives, showing its robustness and synthetic application potential.

One-Pot, Open-Air Synthesis of Flexible and Degradable Multifunctional Polymer Composites with Adhesion, Water Resistance, Self-Healing, Facile Drug Loading, and Sustained Release Properties.

Developing proper wound management via wound dressings represents a global challenge. Ideal wound dressings shall encompass multiple integrated functionalities for variable, complex scenarios; however, this is challenging due to the complex molecular design and synthesis process. Herein, polymer composites, cross-linked poly(styrene oxide-co-hexaphenylcyclotrisiloxane)/crosslinked poly(hexaphenylcyclotrisiloxane) (cP(SO-co-HPCTS)/cPHPCTS) with multiple functionalities are prepared by a one-step, open-air method using catalytic ring-opening polymerization. The introduction of a mobile polymer cP(SO-co-HPCTS) endows the composite with good flexibility and self-healing properties at human body temperature. The hydrophobic groups in the main chain provide hydrophobicity and good water resistance, while the hydroxyl groups contained in the end groups enable good adhesion properties. Drugs can be efficiently loaded by blending and then sustainably release from the polymer composite. The material can rapidly degrade in a tetrahydrofuran solution of tetrabutylammonium fluoride due to its SiOSi bonds. The facile, one-step, open-air synthesis procedure and multiple functional properties integrated into the composites provide good prospects for their extensive application and batch production as wound dressing materials.

Low‐Valent MxAl3Cluster Salts with Tetrahedral [SiAl3]+and Trigonal‐Bipyramidal [M2Al3]2+Cores (M=Si/Ge)

AbstractSchnöckel's [(AlCp*)4] and Jutzi's [SiCp*][B(C6F5)4] (Cp*=C5Me5) are landmarks in modern main‐group chemistry with diverse applications in synthesis and catalysis. Despite the isoelectronic relationship between the AlCp* and the [SiCp*]+fragments, their mutual reactivity is hitherto unknown. Here, we report on their reaction giving the complex salts [Cp*Si(AlCp*)3][WCA] ([WCA]−=[Al(ORF)4]−and [F{Al(ORF)3}2]−; RF=C(CF3)3). The tetrahedral [SiAl3]+core not only represents a rare example of a low‐valent silicon‐doped aluminium‐cluster, but also—due to its facile accessibility and high stability—provides a convenient preparative entry towards low‐valent Si−Al clusters in general. For example, an elusive binuclear [Si2(AlCp*)5]2+with extremely short Al−Si bonds and a high negative partial charge at the Si atoms was structurally characterised and its bonding situation analysed by DFT. Crystals of the isostructural [Ge2(AlCp*)5]2+dication were also obtained and represent the first mixed Al−Ge cluster.

Interaction effects in a two-dimensional AlSi[formula omitted]P nanosheet: A first-principles study on the electronic, mechanical, thermal, and optical properties

Physical quantities such as the electronic, the mechanical, the thermal, and the optical properties of Al and P codoped silicene forming AlSi6P nanosheets are investigated by first-principle calculations within density functional theory. A particular attention of this study is paid to the interaction effect between the Al and the P atoms in the buckled silicene structure. We infer that the interaction type is attractive and it leads to an asymmetry in the density of states opening up a band gap. In contrast to BN-codoped silicene, the buckling in the Al–P codoped silicene is not much influenced by the dopants as the bond lengths of Si–P and Al–P are very similar to the Si–Si bond lengths. On the other hand, the longer bond length of Si–Al decreases the stiffness and thus induces fractures at smaller values of applied strain in AlSi6P. The elastic and the nonelastic regions of the stress–strain curve of AlSi6P depend on the placement of the Al and the P atoms. The finite band gap caused by the Al–P dopant leads to enhancement of the Seebeck coefficient and the figure of merit, and induces a redshift of peaks in the dielectric response, and the optical conductivity. Finally, properties of the real and the imaginary parts of the dielectric function, the excitation spectra, the refractive index, and the optical response of AlSi6P are reported.

Degradation of Diazo Congo Red Dye by Using Synthesized Poly-Ferric-Silicate-Sulphate through Co-Polymerization Process.

The ability of poly-ferric-silicate-sulphate (PFSS) synthesized via a co-polymerization process has been applied for the removal of diazo Congo red dye. A novel degradation pathway of diazo Congo red dye by using PFSS is proposed based on LC-MS analysis. Diazo Congo red dye was successfully removed using synthesized PFSS at lower coagulant dosages and a wider pH range, i.e., 9 mg/L from pH 5 to 7, 11 mg/L at pH 9, and 50 mg/L at pH 11. The azo bond cleavage was verified by the UV-Vis spectra of diazo Congo red-loaded PFSS and FTIR spectra which showed disappearance of the peak at 1584 cm-1 for -N=N- stretching vibrations. The synchronized results of UV-Vis spectra, FTIR, and the LC-MS analysis in this study confirmed the significance of the Si and Fe bond in PFSS towards the degradation of diazo Congo red dye. The successfully synthesized PFSS coagulant was characterized by FTIR, SEM, TEM, and HRTEM analysis. From this analysis, it was proven that PFSS is a polycrystalline material which is favorable for the coagulation-flocculation process. Based on all these findings, it was established that synthesized PFSS can be employed as a highly efficient polymeric coagulant for the removal of dye from wastewater.

Si-H Bond Activation and Dehydrogenative Coupling of Silanes across the Iron-Amide Bond of a Bis(amido)bis(phosphine) Iron(II) Complex.

Despite the utility of Si-Si bonds, there are relatively few examples of Si-Si bond formation by base metals. In this work, a four-coordinate iron complex, (PNNP)FeII, is shown to strongly activate the Si-H bonds in primary silanes across the Fe-amide bonds in a metal-ligand cooperative fashion. Upon treatment with excess silane, Si-Si dehydrogenative homocoupling is shown to occur across the Fe-Namide bond without concomitant oxidation and spin state changes at the Fe center.

Palladium-catalyzed addition of acylsilanes across alkynes via the activation of a C-Si bond.

Palladium-catalyzed addition of a C-Si bond in acylsilanes across the triple bonds in an alkyne bearing a carbonyl group at one terminal is reported. The reaction proceeds with excellent regioselectivity, in which a silyl group is incorporated into the carbon α to the carbonyl group, allowing for straightforward access to a variety of functionalized alkenylsilane derivatives. Catalytic synthesis of indanones by annulation between acylsilanes and alkynes with an identical catalytic system is also reported.

Cycling durability and potentiostatic rejuvenation of electrochromic tungsten oxide thin films: Effect of silica nanoparticles in LiClO4–Propylene carbonate electrolytes

Electrochromic (EC) technology allows control of the transmission of visible light and solar radiation through thin-film devices. When applied to “smart” windows, EC technology can significantly diminish energy use for cooling and air conditioning of buildings and simultaneously provide good indoor comfort for the buildings’ occupants through reduced glare. EC “smart” windows are available on the market, but it is nevertheless important that their degradation under operating conditions be better understood and, ideally, prevented. In the present work, we investigated EC properties, voltammetric cycling durability, and potentiostatic rejuvenation of sputter-deposited WO 3 thin films immersed in LiClO 4 –propylene carbonate electrolytes containing up to 3.0 wt% of ∼7-nm-diameter SiO 2 nanoparticles. Adding about 1 wt% SiO 2 led to a significant improvement in cycling durability in the commonly used potential range of 2.0–4.0 V vs. Li/Li + . Furthermore, X-ray photoemission spectroscopy indicated that O–Si bonds were associated with enhanced durability in the presence of SiO 2 nanoparticles. • Electrochromic properties, durability, and potentiostatic rejuvenation of W oxide thin films are investigated. • The aim was to study the effect of ∼7-nm-diameter silica nanoparticles in LiClO 4 –propylene carbonate electrolytes. • Film degradation was investigated in range between 2.0 and 4.0 V vs. Li/Li + . • Adding about 1 wt% SiO 2 led to a significant improvement in cycling durability. • O–Si bonds were associated with enhanced durability in the presence of SiO 2 nanoparticles.

Organophotocatalytic silyl transfer of silylboranes enabled by methanol association: a versatile strategy for C–Si bond construction

A visible light-induced organophotocatalytic silyl transfer strategy of silylboranes for the construction of C–Si bonds has been demonstrated, where methanol association with boron atoms enables the photocatalytic generation of silyl radicals.

Electronic structure comparisons of isostructural early d- and f-block metal(iii) bis(cyclopentadienyl) silanide complexes.

We report the synthesis of the U(iii) bis(cyclopentadienyl) hypersilanide complex [U(Cp'')2{Si(SiMe3)3}] (Cp'' = {C5H3(SiMe3)2-1,3}), together with isostructural lanthanide and group 4 M(iii) homologues, in order to meaningfully compare metal-silicon bonding between early d- and f-block metals. All complexes were characterised by a combination of NMR, EPR, UV-vis-NIR and ATR-IR spectroscopies, single crystal X-ray diffraction, SQUID magnetometry, elemental analysis and ab initio calculations. We find that for the [M(Cp'')2{Si(SiMe3)3}] (M = Ti, Zr, La, Ce, Nd, U) series the unique anisotropy axis is conserved tangential to ; this is governed by the hypersilanide ligand for the d-block complexes to give easy plane anisotropy, whereas the easy axis is fixed by the two Cp'' ligands in f-block congeners. This divergence is attributed to hypersilanide acting as a strong σ-donor and weak π-acceptor with the d-block metals, whilst f-block metals show predominantly electrostatic bonding with weaker π-components. We make qualitative comparisons on the strength of covalency to derive the ordering Zr > Ti ≫ U > Nd ≈ Ce ≈ La in these complexes, using a combination of analytical techniques. The greater covalency of 5f3 U(iii) vs. 4f3 Nd(iii) is found by comparison of their EPR and electronic absorption spectra and magnetic measurements, with calculations indicating that uranium 5f orbitals have weak π-bonding interactions with both the silanide and Cp'' ligands, in addition to weak δ-antibonding with Cp''.

Evonik P25 photoactivation in the visible range by surface grafting of modified porphyrins for p-nitrophenol elimination in water

<abstract> <p>An Evonik P25 TiO<sub>2</sub> material is modified using a porphyrin containing Si-(OR)<sub>3</sub> extremities to extend its absorption spectrum in the visible range. Two different loadings of porphyrin are grafted at the surface of P25. The results show that the crystallinity and the texture of the P25 are not modified with the porphyrin grafting and the presence of the latter is confirmed by Fourier-transform infrared spectroscopy (FTIR) measurements. All three samples are composed of anatase/rutile titania nanoparticles around 20 nm in size with a spherical shape. The absorption spectra of the porphyrin modified samples show visible absorption alongside the characteristic Soret and Q bands of porphyrin, despite slightly shifted peak values. The <sup>29</sup>Si solid state nuclear magnetic resonance (NMR) spectra show that the porphyrin is linked with Ti–O–C and Ti–O–Si bonds with the Evonik P25, allowing for a direct electron transfer between the two materials. Finally, the photoactivity of the materials is assessed on the degradation of a model pollutant—<italic>p</italic>-nitrophenol (PNP)—in water. The degradation is substantially enhanced when the porphyrin is grafted at its surface, whereas a very low activity is evidenced for P25. Indeed, with the best sample, the activity increases from 9% to 38% under visible light illumination. This improvement is due to the activation of the porphyrin under visible light that produces electrons, which are then transferred to the TiO<sub>2</sub> to generate radicals able to degrade organic pollutants. The observed degradation is confirmed to be a mineralization of the PNP. Recycling experiments show a constant PNP degradation after 5 cycles of photocatalysis of 24 h each.</p> </abstract>

Preparation of chitosan/cellulose composite copper catalyst for green synthesis in the construction of C–Si bonds in aqueous phase

Green and recyclable chitosan/cellulose composite copper gelatinous microbeads were successfully developed for the silylation of α,β-unsaturated acceptors in aqueous phase with a broad substrate scope.

Comparison of group 4 and thorium M(IV) substituted cyclopentadienyl silanide complexes.

We report the synthesis and characterisation of a series of M(IV) substituted cyclopentadienyl hypersilanide complexes of the general formula [M(CpR)2{Si(SiMe3)3}(X)] (M = Hf, Th; CpR = Cp', {C5H4(SiMe3)} or Cp'', {C5H3(SiMe3)2-1,3}; X = Cl, C3H5). The separate salt metathesis reactions of [M(CpR)2(Cl)2] (M = Zr or Hf, CpR = Cp'; M = Hf or Th, CpR = Cp'') with equimolar K{Si(SiMe3)3} gave the respective mono-silanide complexes [M(Cp')2{Si(SiMe3)3}(Cl)] (M = Zr, 1; Hf, 2), [Hf(Cp'')(Cp'){Si(SiMe3)3}(Cl)] (3) and [Th(Cp'')2{Si(SiMe3)3}(Cl)] (4), with only a trace amount of 3 presumably formed via silatropic and sigmatropic shifts; the synthesis of 1 from [Zr(Cp')2(Cl)2] and Li{Si(SiMe3)3} has been reported previously. The salt elimination reaction of 2 with one equivalent of allylmagnesium chloride gave [Hf(Cp')2{Si(SiMe3)3}(η3-C3H5)] (5), whilst the corresponding reaction of 2 with equimolar benzyl potassium yielded [Hf(Cp')2(CH2Ph)2] (6) together with a mixture of other products, with elimination of both KCl and K{Si(SiMe3)3}. Attempts to prepare isolated [M(CpR)2{Si(SiMe3)3}]+ cations from 4 or 5 by standard abstraction methodologies were unsuccessful. The reduction of 4 with KC8 gave the known Th(III) complex, [Th(Cp'')3]. Complexes 2-6 were characterised by single crystal XRD, whilst 2, 4 and 5 were additionally characterised by 1H, 13C{1H} and 29Si{1H} NMR spectroscopy, ATR-IR spectroscopy and elemental analysis. In order to probe differences in M(IV)-Si bonds for d- and f-block metals we studied the electronic structures of 1-5 by density functional theory calculations, showing M-Si bonds of similar covalency for Zr(IV) and Hf(IV), and less covalent M-Si bonds for Th(IV).

Palladium-catalyzed C–Si bond formation via denitrative cross-coupling of nitroarenes with hexamethyldisilane

We disclose a novel protocol for arylsilane via a Pd-catalyzed cross-coupling of hexamethyldisilane with nitroarenes, and the products could be easily transformed into aryl halides, homocoupling products, and aryl boron reagents.

Synthesis of hybrid framework of tenorite and octahedrally coordinated aluminosilicate for the robust adsorption of cationic and anionic dyes

Adsorption is an important process for the industrial dye effluent treatment. Many adsorbents are employed such as activated carbon, metal oxide, molecular sieves etc. All those adsorbents are having their own setbacks like longer adsorption time and lower adsorption capacity. So development of fast adsorption and higher adsorption capacity is very much essential. In this view, we synthesized hybrid crystal system of tenorite and aluminosilicate framework (CuO@AS) for the faster adsorption. It is characterized by FT-IR, HRTEM and WAXRD. WAXRD proved the hybridization of two crystal systems viz tenorite & alumina in monoclinic phase and silica in trigonal phase. The crystal structure drawn based on the WAXRD data. It is observed that the tenorite and aluminosilicate framework are separate, but they are interlinked through Cu–O–Al and Cu–O–Si bond. This interconnection makes the aluminium in six coordination and Cu in four coordination. Aluminium and copper has 3 and 2 Brønsted acid sites respectively. Moreover, copper has three more OH group, so totally 5 H+ and 3 OH− sites in copper and aluminium are responsible for the faster adsorption with high adsorption capacity compared to reported literature. To test the adsorption tendency, Victoria Blue (VB) and Metanil Yellow (MY) dyes are employed at room temperature. The rate constant of Pseudo-second order kinetics for the VB and MY are 0.002462 g mg−1 min−1 and 0.001619 g mg−1 min−1 which indicated faster adsorption of VB than MY. Moreover, total adsorption capacity for VB (636 mg/g) is higher than MY (52 mg/g). This is due to the hybridization of tenorite and aluminosilicate. Thermodynamic data such as ΔG°, ΔH° and ΔS° revealed that the adsorption is spontaneous, chemisorption and highly disordered in the adsorbent-adsorbate interface. This disorderness is due to the disordered pores present in the material.

Structural, optical behavior and Judd-Ofelt analysis of europium-doped silicophosphate glasses for red-emitting device applications

Silicophosphate glasses doped with europium are of great interest in fundamental fields such as photonics, luminous diodes, optoelectronics, and lasers. In the present study, we have focused on exploring the effect of the europium (Eu3+) dopant on the structural, physical, and optical properties of silicophosphate glasses. In this study, pure and europium-doped silicophosphate glasses were synthesized by using the sol-gel method. To evaluate the structural and optical properties of the prepared glasses, X-ray diffraction (XRD), Fourier transform infrared (FTIR), UV–visible spectroscopy, photoluminescence spectra, and luminescence decay of trivalent europium ions in glasses were examined. XRD revealed that all of the synthesized glasses contained amorphous phases. FTIR transmittance spectra demonstrated that the addition of europium in the silicophosphate glass leads to a reduction in the dimensionality of the network as a result of the rupture of the Si–O–Si bonds into their structure. The band gap energy of the samples increases with the dopant of europium. The photoluminescence spectrum shows the line characteristics of the Eu (III) ion 5D0→7FJ (J = 0, 1, 2, 3 and 4). Large bands were observed, suggesting non-homogeneous sites that are characteristics of amorphous systems. The intensity parameters ΩJ (J = 2, 4) and the radiative properties of Eu3+ ions in the prepared glasses, such as the stimulated emission cross-section (σe), transition probability (A), radiative lifetime (τcal), and branching ratio (βR) were determined, and Eu3+ emission may be suggested for suitable laser applications due to its high value of βR=52.71%. Furthermore, the CIE 1931 color coordinates of the synthesized glass (x, y) are within the range of (0.63, 0.36) and are quite close to the standard red color (0.67, 0.33), indicating that pure bright red emission has been achieved. The obtained results show that the europium-doped silicophosphate glasses can be appropriate for use as a red laser material.