The determination of local structural units in amorphous SiBN3C by means of X-ray photoelectron and X-ray absorption spectroscopy

X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) spectroscopy at the K-edge of Si, N, and B are presented as techniques suited to determine structural units in amorphous SiBN(3)C. The measurements reported give evidence for the presence of tetrahedral (SiN(4))- and planar (BN(3))-groups. It is concluded that these structural elements dominate the atomic surroundings of B and Si, respectively. From the spectroscopic results we conclude that C is mainly bonded to N and is not present as a pure carbide.     

An X-ray photoelectron spectroscopic study of novel SiON glasses

Novel SiON glasses obtained by melting mixtures of crystalline α-SiO₂ and α-Si₃N₄ were investigated by means of X-ray photoelectron spectroscopy (XPS). The incorporation of nitrogen into the SiO₂ network was recently proved by ²⁹Si-MAS-NMR (magic-angle spinning nuclear magnetic resonance) and Si K-XANES (X-ray absorption near edge structure). The Si 2p XPS and the Si KLL XAES (X-ray excited Auger electron spectroscopy) studies of the SiON glasses confirm the formation of mixed structural units (SiO_xN_4-x) by the presence of an additional spectral component energetically located between SiO₂- and Si₃N₄-like signals. The N 1s and O 1s XPS spectra support the conclusion about the incorporation of nitrogen into the SiO₂ network.     

Chemistry of silicon-nitrogen compounds. 165. On the crystalline products from the reaction of silicon tetrachloride with nitrogen in a glow discharge. Single crystal X-ray structure determination of N(SiCl3)3 and Cl3SiN(SiCl2)2NSiCl3

Of the two crystalline products obtained by reacting a silicon tetrachloride/nitrogen mixture in a glow discharge tube, the more volatile (m. p. 78°C) has been confirmed to be tris(trichlorosilyl)amine NSi₃Cl₉ whereas the less volatile component (m. p. 66°C) has been identified as N,N′-bis(trichlorosilyl)-Si,Si′-tetrachloro-cyclodisildiazane N₂Si₄Cl₁₀. These conclusions are supported by mass and vibrational spectroscopy and single crystal X-ray structures. NSi₃Cl₉ possesses a nearly planar NSi₃ skeleton with average N? Si distances of 1.734(2) Å. The N₂Si₄ fragment of N₂Si₄Cl₁₀ is roughly planar with endocyclic N? Si? N and Si? N? Si angles of 89.2(1) and 90.8(1)°, respectively, and mean N? Si distances of 1.731(3) (endocyclic) and 1.687(3) Å (exocyclic).     

Quantitative analysis of elements (C, N, O, Al, Si and Fe) in polyamide with wavelength dispersive X-ray fluorescence spectrometry

A wavelength dispersive X-ray fluorescence (WD-XRF) spectrometry combined with calibration curve method was established for simultaneously analyzing low-Z elements (C,N,O) and Al,Si,Fe in polyamide.To investigate the origin of plastic material causing deposition and blocking in instrument engines and pipelines,polyamide 6 (PA 6,an engineering plastic) was chosen as the study object on account of its common use in industry.The sample preparation with pressed powder disk has been developed for determination of six elements in PA 6.Pure Cu metal was used as the matrix and PA 6 was regarded as standard sample for C,N,O elements.PA 6 particles were firstly smashed to uniform powder in liquid nitrogen,and then mixed with inorganic standard powders (Fe2O3,Al2O3,SiO2,and Na 2 SiO 3).The mixture was ground to obtain homogeneous calibration materials for WD-XRF analysis.The quantitative property of the calibration curve method for each element was reliable.The limits of detection (S/N≤3) of C,N,O,Al,Si and Fe using WD-XRF were 249,120,101,6.2,3.3,and 1.8 μg/g,respectively.To confirm the accuracy of the proposed WD-XRF calibration curve method,inductively coupled plasma optical emission spectroscopy (ICP-OES) detection for Al,Si,Fe and elemental analyzer (EA) analysis for C,N,O were utilized.A good correlation of the WD-XRF results with the measurements of ICP-OES and EA was observed.     

X-ray analysis of 1,3-dioxa-6-aza-2-silacyclooctane derivatives

X-ray analysis has been conducted on four dioxaazasilacyclooctanes R₂Si(OCH₂CH₂)₂NR′ with R = C₆H₅, R′ = CH₃ (IV); R = C₆H₅, R′ = (CH₃)₃C (V); R = CH₃, R′ = C₆H₅ (VI) and R = R′ = C₆H₅ (VII). The interatomic distances SiN measured for these compounds had the values: 2.68 (IV), 3.16 (V), 3.19 (VI) and 3.08 Å (VII), indicating weak nitrogen—silicon interaction and a virtual lack of coordinate Si ← N bonding. The data of other authors and our own evidence suggest that the Si ← N interaction in these compounds is strongly influenced by the electronic effects of Si- and N-substituents and, in particular, by the steric effects of the latter.     

Analytical characterization of BCxNy films generated by LPCVD with triethylamine borane

Triethylamine borane (TEAB) and He, N₂ or NH₃ were applied as additional reaction gases in the production of BC_xN_y layers by low-pressure chemical vapor deposition (LPCVD). These layers were deposited on Si(100) wafers and characterized chemically by X-ray photoelectron spectroscopy (XPS) and synchrotron radiation-based total-reflection X-ray fluorescence analysis combined with near-edge X-ray absorption fine-structure spectroscopy (TXRF-NEXAFS). The composition of the material produced without NH₃ was found to be dominated by B–C bonds with the stoichiometric formula B₂C₃N. B–N bonds with the formula B₂CN₃ were preferred when NH₃ was added. A first attempt was made to compare the results obtained by applying trimethylamine borane and TEAB as single-source precursors.     

Synthesis and Molecular Structure of Tris[(trimethylsilyl)silyl](diisopropylamino)(diphenylphosphino)borane

The 1:1 reaction of [(Me₃Si)₃SiLi·3THF] with (iPr₂N)BCl₂ in hexane provides [{(Me₃Si)₃Si}·(iPr₂N)BCl] ( 2 ) in good yield as a colorless crystalline solid. This compound combined in a 1:1 ratio with LiPPh₂ in DME gives [{(Me₃Si)₃Si}·(iPr₂N)B(PPh₂)] ( 3 ) as a yellow crystalline solid. The new compounds were characterized by IR, MS and ¹H, ¹³C{¹H} and ¹¹B NMR spectroscopy and the molecular structure of 3 was determined by X‐ray structure analysis.     

Low-Pressure Chemical Vapor Deposition of Silicon Carbide Thin Films from Organopolysilanes

(Me₃Si)₂SiMe₂, (Me₃Si)₃SiMe and (Me₃Si)₄Si were used as precursors for the deposition of polycrystalline β-SiC thin films on silicon substrates at 1000–1200°C in a low-pressure hot-wall chemical vapor deposition reactor. The thin films were analyzed by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy.     

Synthesis,Structure, and Reactivity of Diazene Adducts: Isolation of iso‐Diazene Stabilized as a Borane Adduct

This work describes the synthesis and full characterization of a series of GaCl₃ and B(C₆F₅)₃ adducts of diazenes R¹?N?N?R² (R¹=R²=Me₃Si, Ph; R¹=Me₃Si, R²=Ph). Trans‐Ph?N?N?Ph forms a stable adduct with GaCl₃, whereas no adduct, but instead a frustrated Lewis acid–base pair is formed with B(C₆F₅)₃. The cis‐Ph?N?N?Ph ? B(C₆F₅)₃ adduct could only be isolated when UV light was used, which triggers the isomerization from trans‐ to cis‐Ph?N?N?Ph, which provides more space for the bulky borane. Treatment of trans‐Ph?N?N?SiMe₃ with GaCl₃ led to the expected trans‐Ph?N?N?SiMe₃ ? GaCl₃ adduct but the reaction with B(C₆F₅)₃ triggered a 1,2‐Me₃Si shift, which resulted in the formation of a highly labile iso‐diazene, Me₃Si(Ph)N?N; stabilized as a B(C₆F₅)₃ adduct. Trans‐Me₃Si?N?N?SiMe₃ forms a labile cis‐Me₃Si?N?N?SiMe₃ ? B(C₆F₅)₃ adduct, which isomerizes to give the transient iso‐diazene species (Me₃Si)₂N?N ? B(C₆F₅)₃ upon heating. Both iso‐diazene species insert easily into one B?C bond of B(C₆F₅)₃ to afford hydrazinoboranes. All new compounds were fully characterized by means of X‐ray crystallography, vibrational spectroscopy, CHN analysis, and NMR spectroscopy. All compounds were further investigated by DFT and the bonding situation was assessed by natural bond orbital (NBO) analysis.     

Synthesis and Characterization of Benzonitrile-Substituted Silyl Ethers

The silyl ethers (siloxanes) Me_{4? x}Si(OC₆H₅CN)_x (x = 1–4) (1–4), O(Si(OC₆H₄CN) (Me)₂)₂ (5), and Me₃Si–O–C₆F₄CN (6) have been synthesized by the reaction of the respective p-hydroxybenzonitriles and chlorosilanes in the presence of N,N,N′,N′-tetramethylethylenediamine (TMEDA) as hydrogen chloride acceptor. All compounds have been fully characterized by CHN-analysis, melting point, IR, Raman, mass spectroscopy, and ¹H, ¹³C, ²⁹Si NMR spectroscopy. Furthermore, the crystal structures of these compounds—with the exception of Me₂Si(OC₆H₅CN)₂, which is a liquid—were determined by X-ray diffractometry.     

Synthesis and X-ray structure of 1,1-dimethylhydrazinium azide

1,1-Dimethylhydrazinium azide, [ (CH₃)₂NH–NH₂] [N₃], was prepared in high yield from 1,1-dimethylhydrazine and HN₃ in CH₂Cl₂ solution at −20°C. The new compound has been fully characterized by elemental analysis, multinuclear NMR (¹H, ¹³C, ¹⁴ N, ¹⁵ N) and vibrational spectroscopy (IR, Raman). The structure in the solid state was determined by a low temperature (173 K) single crystal X-ray diffraction analysis.     

Comparative study by single crystal X-ray structure determinations of tetramethylaminoborane and tetramethylethene at 110 K

The single crystal structures of the two isoelectronic and isosteric compounds tetramethylaminoborane and tetramethylethene have been determined by an X-ray study at 110 K. The distances of the central bonds are refined to 140.3(1) pm (B=N) and 134.8(1) pm (C=C), the CXXC-torsion angles (XX=CC, BN) are smaller than 1° in both compounds. A bond-length-bond-order correlation for the aminoboranes [(CH₃)₂N] _n B(CH₃)_3–n withn=1, 2, and 3 give a regression coefficient of 0.9977, the same is found for the CNC-angle as a function of the CBNC-torsion angle. Also, the comparison among these aminoboranes show that the variation of CBNC-torsion angles has more influence on bond lengths at small angles.     

A study of the electronic structure of phenylsilanes by X-ray emission spectroscopy and quantum chemical calculation methods

The electronic structure of a series of phenylsilanes Ph_4?n SiH _n (n = 0?C3) is studied by X-ray emission spectroscopy and quantum chemical calculations by the density functional theory method. Based on the calculations theoretical X-ray emission SiK??₁ spectra of phenylsilanes Ph_4?n SiH _n (n = 0?C4) are constructed and their energy structure and shape turn out to be well consistent with experiment. The distribution of the electron density of states with different symmetry of Si, C, H atoms are also constructed. An analysis of the obtained X-ray fluorescent SiK??₁ spectra and the distribution of the electron density of states in Ph₄Si and Ph₃SiH compounds shows that their energy structure is mainly determined by a system of the energy levels of phenyl ligands weakly perturbed by interactions with valence AOs of silicon. In the energy structure of MOs of the PhSiH₃ compound, energy orbitals related to t ₂ and a ₁ levels of tetrahedral SiH₄ are mainly presented.     

Thermolysis of [tris(trimethylsilyl)methyl](diphenyl)fluorosilane. Isomerization of a sila-olefin intermediate

The compound (Me₃Si)₃CSiPh₂F loses Me₃SiF under reflux or on passage through a tube at 450°C to give three products, A, B, and C, in approximately 20/20/60 ratio. Products A and B, which are solids, were shown by X-ray crystallographic analysis to be the diastereoisomeric forms of 1-dimethylsila-2-trimethylsilyl-3-[(methyl)(phenyl)sila]indane. From its mass and ¹H NMR spectra, C (a liquid) was tentatively identified as 1,3-bis(dimethylsila)-2-[(dimethyl)(phenyl)silyl]indane. All three products are isomers of the sila-olefin (Me₃Si)₂CSiPh₂, and it is suggested that the latter is first formed by loss of Me₃SiF from (MeSi)₃CSiPh₂F, and the equilibrium (Me₃Si)₂CSiPh₂ ? (Me₃Si)(Ph₂MeSi)CSiMe₂ ? (Me₃Si)(PhMe₂Si)CSiMePh ? (Me₂PhSi)₂CSiMe₂ is then rapidly established; internal cyclizations involving addition of aryl CH bonds across SiC bonds then occur to give the observed products. Consistent with this is the observation that a mixture of silicon alkoxides, thought to be (Me₃Si)₂CHSiPh₂OMe and its isomers (which would be formed by addition of methanol across the SiC bonds of the four sila-olefins) is produced when methanol is passed through the hot tube with the (Me₃Si)₃CSiPh₂F.Full structural details are given for compounds A and B. Some features of interest are: (a) the conformation of the 5-membered ring is different in the two diastereoisomers; (b) the exocyclic SiCSiMe₃ bond angles, of ca. 120° are unusually large; and (c) there is a little distortion of the fused benzene ring, which is attributed to the effect of silicon substituents on the hybridization of carbon atoms to which they are attached.     

Oxyfluorinated compounds with open structure XI. Interaction between the ULM-3 type framework and linear diamine templates of different chain lengths studied by X-ray diffraction and solid-state nuclear magnetic resonance characterization

The synthesis and structural characterization of oxyfluorinated microporous gallophosphates with the ULM-3 type are presented. This material is hydrothermally prepared (180°C, autogenous pressure, 24 h) by using linear diamines [H₂N(CH₂)_3–5NH₂] as templates. The structures of the phases obtained with the variable organic chain lengths were examined by single-crystal X-ray diffraction (XRD) and ³¹P, ¹⁹F, ¹³C solid-state nuclear magnetic resonance (NMR) spectroscopy. This study showed that the relative flexibility of the C₃C₅ diamines allows the preservation of the topology of the type ULM-3. In this series, the presence of fluorine, which is found in the bridging position between two gallium atoms, is strongly correlated to the existence of hydrogen bonds with ammonium groups of the organic molecules.     

Borazine Based Molecular Single Source Precursors for Si/B/N/C Ceramics

The family of borazines [(SiCl₃)NB(Cl_n(CH₃)_1–n]₃ was synthesized and characterized by NMR and IR spectroscopy, as wellas by single crystal structure analysis. After cross‐linking with methylamine, a soluble polymer was obtained that was transformed to anall‐inorganic random network of nominal composition Si_1.0B_1.0N_3.0C_0.9O_0.1 (idealized SiBN₃C) at 1400 °C. With an on‐set of weight loss at 1840 °C and a resistance against rapid oxidation in pure oxygen of up to 1300 °C, the new Si/B/N/C ceramic shows a high temperature performance similar to those of previously reported Si/B/N/C materials.     

Comparisons of glow discharge polymerization between hexamethyldisilazane and trimethylsilyldimethylamine

Glow discharge polymerization between hexamethyldisilazane (HMDSZ) and trimethylsilyldimethylamine (TMSDMA) was compared by means of infrared spectroscopy and ESCA analysis. Infrared spectra pointed out differences in chemical structure between the polymers prepared from the two monomers, although the two polymers were mainly composed of resembling units such as Si? CH₃, Si? CH₂, Si? H, Si? O? Si, and Si? O? C groups: (i) The polymers prepared from TMSDMA contained N → O group, but the polymers from HMDSZ did not contain this group. (ii) Influences of the W/FM parameter (W is the input energy of rf power, F the flow rate of the monomer, and M the molecular weight of the monomer) appeared on decreasing the C? N group and increasing the C?O group in the TMSDMA system, but little influence appeared in the HMDSZ system. ESCA spectra (C_1s, Si_2p, and N_1s core levels) supported the differences between the two polymers elucidated by infrared spectroscopy, and pointed out differences in susceptibility of the Si? N bond to plasma: The N? Si sequence of TMSDMA was completely ruptured in discharge to yield polymers, and the Si? NH? Si sequence of HMDSZ remained in considerable amount.     

Structure of novel N-fluorosilylmethyl-N-isopropylureas

Novel N-isopropyl-N',N'-dimethyl-N-(silylmethyl)ureas Me₂NC(O)N(Prⁱ)CH₂SiMe_nX_3–n (X = OEt, F; n = 0–2) were synthesized, and their structure was confirmed by ¹H, ¹³C and ²⁹Si NMR spectroscopy. According to NMR data, the silicon atom of the fluorosilanes (X = F) is pentacoordinated. The X-ray diffraction analysis of the (trifluorosilyl)methylcontaining urea showed that it exists as (O–Si) chelate with intramolecular dative bond C=O→Si (1.880 Å).     

Synthesis and structure of <Emphasis Type="Italic">N</Emphasis>-(2-silatranylethyl)imidazoles

Organosilicon imidazole derivatives containing a 2-silatranylethyl [N(CH₂CH₂O)₃Si(CH₂)₂] group on the nitrogen atom were synthesized, and their steric and electronic structures, including the nature of interaction between the imidazole and silatrane fragments, were studied by X-ray analysis and ¹H, ¹³C, and ²⁹Si NMR spectroscopy.     

Regioselective synthesis of 5-aminopyrazoles from reactions of amidrazones with activated nitriles: NMR investigation and X-ray structural analysis

N-Arylbenzamidrazones and ethyl 2-cyano-3-ethoxybut-2-enoate reacted together in ethanol and catalyzed by triethylamine (Et₃N) to give 5-amino-3-methyl-1-(aryl(phenylimino)methyl)-1H-pyrazole derivatives. Reaction of the target amidrazones with bis-(methylthio)methylidene)malononitrile in EtOH/Et₃N/DMF mixture proceeded to give the corresponding 5-aminopyrazoles. The structure of the obtained products was proved by IR, mass, and NMR spectra and elemental analyses. Two-dimensional NMR spectroscopy and X-ray structural analyses were used to differentiate the assigned structures from other possible ring systems and regioisomers. The reaction mechanism is discussed.