Phenyl Bonds Research Articles

Combining infrared and Raman spectra to assess MDI localization in novel flax-reinforced automotive composites

The present work describes the use of novel flax preforms reinforcement as substitution of glass fibres in complex composite stackings made of polyurethane foam impregnated with methylene diphenyl 4, 4′-diisocyanate (MDI), for automotive headliner parts manufacturing. Headliner structure, cohesion and mechanical performances are highly dependant of MDI distribution in both foam and fibre network. This study monitors the presence and localization of MDI in the final biobased composite by implementing a robust and innovative spectroscopic methodology. For that, Infrared and Raman spectroscopies are used to characterize the fibres and polymer chemical groups, such as the isocyanate and phenyl bonds in MDI and the urethane group. MDI in the flax preform is identified by the signal of the isocyanate group in the infrared spectrum. The complementary Raman study highlight two signatures of the interaction between polyurethane and MDI. One is the shift from 1620 to 1610 cm−1 between the urethane and the MDI aromatic vibration. The second is the aromatic ring substitution at 1530 cm−1, which increases with the MDI concentration in the composite. These investigations demonstrate that MDI is present on the surfaces of flax fibres and foam and at the foam/fibre interfaces in the composite. The results clearly demonstrate the potential of flax for a use as headliner reinforcement, without penalizing the structure of the part.

Three isomeric 4-[(n-bromophenyl)carbamoyl]butanoic acids (n = 2, 3 and 4) as DNA intercalator: Synthesis, physicochemical characterization, antimicrobial activity, antioxidant potential and in silico study

A series of three isomeric 4-[(n-bromophenyl)carbamoyl]butanoic acids (n = 2, 3 and 4) were synthesized and their structures were confirmed by FTIR, NMR, MS, micro elemental analysis (CHN) and single crystal X-ray crystallography. Kinks are noted in the molecular structures of the n = 2 and n = 3 compounds, namely about the methylene-C–C(carbonyl) and N–C(phenyl) bonds; no such twist about the former bond is seen in the n = 4 molecule. In the molecular packing, supramolecular tapes are evident, being constructed by orthogonally orientated O-H…O(carbonyl) and N-H…O(amide) hydrogen bonds. The synthesized compounds interact with salmon sperm DNA via an intercalative mode as confirmed by the UV-visible spectroscopic and viscometric techniques. The results of antimicrobial activity performed against five bacterial and two fungal strains show that these compounds have < 50% inhibition. Compound 3 has shown the maximum of 78% DPPH scavenging activity. SwissADME webserver was used for in silico study of the screened compounds and it was found that they obey the rules of drug-likeness and exhibit good potential for bioavailability.

Composition of low molecular weight impurities in dimethylmethylpheylsiloxane rubbers with terminal hydroxyl groups

Synthesis of dimethylmethylphenylsiloxane rubbers with terminal hydroxyl groups by copolymerization of cyclosiloxanes can be accompanied by formation of low molecular weight compounds, impurities, which are difficultly removed (due to target product affinity) and can lead to rubber opalescence. Identification of the impurities (the content of each impurity ≥ 10 –4 wt.% in 1 μ l of the sample) can be carried out using a sensitive gas chromatography-mass spectrometric method. The method allows separation of the analyzed mixture into individual components on a capillary column. These components enter a mass analyzer and undergo electron ionization which leads to their dissociation into pairs «cation – neutral fragment». Only positively charged ions are observed in the mass spectra, which provides the possibility of predicting the structure of the analyzed siloxane impurities. Rearrangement of linear and cyclic molecules occurring upon mass spectrometric fragmentation result in their transformation into cyclic and bicyclic cations. The structure of the cations formed under ionization conditions depends on the number of silanol bonds and their location in the molecule. To prove the presence of compounds with hydroxyl groups in the composition of impurities and to demonstrate the effect of electron ionization on the fragmentation of compounds with silanol bonds, a sample of oligomethylsiloxane with terminal trimethylsiloxy groups was synthesized in a similar way using the copolymerization method. Compounds with silanol bonds present in the composition of the impurities appear as chromatographic asymmetric peaks with ascending and descending gently sloping zones. Those compounds are rearranged either when passing through a chromatographic column due to sorption-desorption and enter the detector in a modified form or drift through the column and undergo rearrangements already under conditions of electron ionization. The impurities contained linear and cyclic methylsiloxanes with silanol and phenyl bonds. The chromato-mass spectrometric method provide a reliable control of the composition and content of undesirable impurities which cause rubber opalescence.

Relayed Proton Brake in N-Pyridyl-2-iso-propylaniline Derivative: Two Brakes with One Proton.

The addition of methanesulfonic acid to N-(2,6-dimethylpyridin-4-yl)-N-methyl-2-iso-propylaniline led to the selective protonation of the pyridine nitrogen atom, resulting in a significant deceleration of the rotation rates around both N-pyridyl and N-(i-Pr)phenyl bonds through a relayed brake mechanism.

Microwave-Assisted Catalytic Cleavage of C–C Bond in Lignin Models by Bifunctional Pt/CDC-SiC

We herein reported a microwave-assisted catalytic cracking (MACC) strategy for 5-5′ C(phenyl)–C(phenyl) bonds cleavage using 2,2′-biphenol (2-BP) as the kraft lignin model. A microwave absorbent of SiC was modified as the catalyst carrier for the carbide-derived carbon (CDC) layer to form CDC-SiC; subsequently, the Pt/CDC-SiC catalyst was prepared. Pt/CDC-SiC exhibited a high selectivity to monomers with total mass yields of 49.3 wt %. The conversion rate increased from 17.1% to 85% with Pt/CDC-SiC under the dynamic vapor flow reaction system. Methanol vapor can produce hydrogen and methyl radicals under microwave irradiation and decrease the activation barrier of the C–C bond cleavage.

The linkage between reversible Friedel–Crafts acyl rearrangements and the Scholl reaction

Friedel–Crafts acyl rearrangements in PPA (at 80–240 °C) and Scholl reactions in AlCl3/NaCl (at 140–220 °C) of benzoylnaphthalenes and fluorobenzoylnaphthalenes have been studied experimentally as a function of temperature and time and computationally. 1BzNA, 2BzNA, 1-4FBzNA, 2-4FBzNA, 1-3FBzNA, 2-3FBzNA, 1-2FBzNA, and 2-2FBzNA were synthesized by classical Friedel–Crafts acylations of naphthalene with benzoyl chloride, benzene with 2-naphthoyl chloride, fluorobenzene with 1- and 2-naphthoyl chlorides and of naphthalene with fluorobenzoyl chlorides, and served as substrates in the investigation. Their structures have been determined by X-ray crystallography and verified by their 1H-, 13C-, and 19F-NMR spectra. 1BzNA, 1-4FBzNA, 1-3FBzNA, and 2-2FBzNA crystallized as the E-diastereomers, whereas 2BzAN, 1-2FBzAN, 2-4FBzAN, and 2-3FBzAN crystallized as the Z-diastereomers. The deviations of the carbonyl group from the naphthyl plane were higher as compared with the deviations from the phenyl plane and were considerably higher in the α-naphthyl ketones than in the β-naphthyl ketones. Intermolecular interactions due to C–H···O and/or C–H···F contacts in the crystal structures of 1E-4FBzNA and 1E1′E-3FBzAN have been revealed. 1BzNA rearranged in PPA under argon to 2BzNA via deacylation to naphthalene (e.g., 140 °C, 10 h) and underwent a regioselective intramolecular cyclodehydrogenation at high temperatures to the Scholl reaction product 7H-benz[de]anthracen-7-one (BdeAN) (e.g., 200 °C, 6 h). At 80 °C, benzene was isolated. 2BzNA underwent in PPA deacylation to naphthalene (e.g., 160 °C, 6 h) and an intramolecular cyclodehydrogenation to BdeAN at high temperatures (e.g., 220 °C, 6 h), necessarily via the putative intermediate 1BzNA. Higher yields of the acyl rearrangement and the Scholl reaction products were obtained under oxygen. 1-4FBzNA and 2-4FBzNA reacted in PPA analogously to 1BzNA and 2BzNA, respectively, with the following exceptions: 2-4FBzNA underwent an acyl rearrangement in PPA to 1-4FBzNA at 260–300 °C, without any formation of the Scholl reaction product 10FBdeAN. 1-4FBzNA also did not yield 10FBdeAN. 1-2FBzNA and 2-2FBzNA behaved similarly. The formation of naphthalene and benzene in the deacylation steps indicated cleavages of both the 1- and 2-naphthyl–benzoyl bonds and the 1- and 2-naphthoyl–phenyl bonds to give naphthalene and benzoylium cation and benzene and 1- and 2-naphthoylium cation, respectively. At 80–100 °C, 1-2FBzNA, 1-3FBzNA, and 1-4FBzNA underwent deacylations to fluorobenzene in PPA, followed by reacylation, each giving a mixture of the three 1-fluorobenzoylnaphthalenes. 2FBzNA, 2-3FBzNA, and 2-4FBzNA behaved similarly, each giving a mixture of the three 2-fluorobenzoylnaphthalenes. The results taken together verified the reversibility of the 1-BzNA⇌2BzNA acyl rearrangements in PPA. The Scholl reaction (AlCl3/NaCl) of 1BzNA (e.g., at 140 °C) gave BdeAN and 2BzNA, whereas 2BzNA gave only BdeAN (at 200–220 °C). 1-4FBzNA and 2-4FBzNA gave (at 200–220 °C) only 2-4FBzNA and 1-4FBzNA, respectively. All the six FBzNA isomers failed to undergo Scholl reaction cyclodehydrogenations to give any FBdeAN isomer. A linkage between the Friedel–Crafts acyl rearrangements and the Scholl reaction has thus been established. A systematic DFT study at B3LYP/6-311(d,p)/PCM (formic acid)) substantiated the predicted mechanism and the reversibility of the acyl rearrangements of benzoylnaphthalenes, in which 1BzNA and 2BzNA are the kinetically controlled and the thermodynamically controlled products, respectively. The DFT-calculated Gibbs free-energy of the transition-state (1Z-1BzNH+ ➔➔ 2σ-2BzNA) in the Friedel–Crafts acyl rearrangement of 1Z-BzNA is considerably lower than the transition state of the cyclization step in the arenium-cation mechanism of the Scholl reaction, in line with experiment, which indicated higher temperatures for the Scholl reaction. DFT calculations of the dication pathway of the Scholl reaction of the E- and Z-diastereomers/conformers of 1BzNA confirmed the preference of the formation of BdeAN versus BaFL, consistently with experiment.

Oxygen Atom Insertion into Iron(II) Phenyl and Methyl Bonds: A Key Step for Catalytic Hydrocarbon Functionalization

Oxy-functionalization of metal–alkyl and −aryl bonds is a key step in potential hydrocarbon oxidation catalysis. However, well-defined examples of M–R to ROH conversion are rare, especially for first-row transition metals. Cp*Fe(CO)(NCMe)Ph reacts with oxygen or hydrogen peroxide to produce benzoic acid. Removing CO from the Cp*Fe(L)(L′)Ph framework allows simple oxygen atom insertion into the Fe–Ph bond. Cp*Fe(P(OCH2)3CEt)2Ph reacts with Me3NO in THF to produce PhOH in high yield when Brønsted acids are added. Studies show that light promotes P(OCH2)3CEt dissociation from Cp*Fe(P(OCH2)3CEt)2Ph, which facilitates the conversion to PhOH. The methyl analogue Cp*Fe[P(OCH2)3CEt]2Me reacts with oxidants to produce MeOH.

Breaking the regioselectivity rule for acrylate insertion in the Mizoroki–Heck reaction

In modern methods for the preparation of small molecules and polymers, the insertion of substrate carbon-carbon double bonds into metal-carbon bonds is a fundamental step of paramount importance. This issue is illustrated by Mizoroki-Heck coupling as the most prominent example in organic synthesis and also by catalytic insertion polymerization. For unsymmetric substrates H(2)C = CHX the regioselectivity of insertion is decisive for the nature of the product formed. Electron-deficient olefins insert selectively in a 2,1-fashion for electronic reasons. A means for controlling this regioselectivity is lacking to date. In a combined experimental and theoretical study, we now report that, by destabilizing the transition state of 2,1-insertion via steric interactions, the regioselectivity of methyl acrylate insertion into palladium-methyl and phenyl bonds can be inverted entirely to yield the opposite "regioirregular" products in stoichiometric reactions. Insights from these experiments will aid the rational design of complexes which enable a catalytic and regioirregular Mizoroki-Heck reaction of electron-deficient olefins.

Simulated glass transition in free‐standing thin polystyrene films

AbstractIn this article, we investigate the glass transition in polystyrene melts and free‐standing ultra‐thin films by means of large‐scale computer simulations. The transition temperatures are obtained from static (density) and dynamic (diffusion and orientational relaxation) measurements. As it turns out, the glass transition temperature of a 3 nm thin film is ∼60 °K lower than that of the bulk. Local orientational mobility of the phenyl bonds is studied with the help of Legendre polynomials of the second‐order P2(t). The α and β relaxation times are obtained from the spectral density of P2(t). Our simulations reveal that interfaces affect α and β‐relaxation processes differently. The β relaxation rate is faster in the center of the film than near a free surface; for the α relaxation rate, an opposite trend is observed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1160–1167, 2010

A DFT characterization of the structures and UV/vis absorption spectra of mauveine dyes

The equilibrium structure of the mauveines has been studied with the density functional theory. The molecular framework consists of a planar diaminophenazine with a centrally appended perpendicular phenyl ring and a laterally bound twisted aminophenyl group. Of the three aromatic fragments, it is only the aminophenyl part that exhibits a conformational flexibility around the C(phenazine)–N–C(phenyl) bonds. The electronic absorption spectra have been examined using hybrid time-dependent density functional theory. The π → π ∗ excitations, mainly occurring in the phenazine moiety, are the major contributors to the strong absorption bands. Intramolecular π-charge transfer from the appended phenyl rings to the phenazine nucleus give rise to weakly-allowed transitions.

Ligand Dissociation and Core Fission from Diphosphine-Protected Gold Clusters

Highly monodisperse samples of diphosphine ligand (1,3-bis(diphenylphosphino)propane- or 1,5-bis(diphenylphosphino)pentane)-protected gold nanoparticles form rapidly in a mixed methanol/chloroform solvent environment. Methanol soluble octagold, decagold, and undecagold monolayer protected clusters yield very stable ion currents when introduced into a mass spectrometer via electrospray ionization. In addition to neutral ligand loss pathways, collision-induced dissociation generates [AuL]+ and [Au3L]+ (L = diphosphine ligand) as particularly stable product ions from all clusters considered. Furthermore, deca- and undecagold clusters are found to be more resistant to collision induced dissociation, and more susceptible to partial ligand losses than octagold clusters. This suggests that for the deca- and undecagold species, Au−P and P−Ph (Ph = phenyl) bonds within the ligand-protected clusters are of comparable strength.

Ethylene Trimerization Catalysts Based on Chromium Complexes with a Nitrogen-Bridged Diphosphine Ligand Having ortho-Methoxyaryl or ortho-Thiomethoxy Substituents: Well-Defined Catalyst Precursors and Investigations of the Mechanism

Chromium-based ethylene trimerization catalyst precursors ((PNP^(OMe)_(-d)_(12))CrPh_3 (4) and (PNP^(OMe)_(-d)_(12))CrPh_2Cl (7)) having a bis(diphenylphosphino)amine ligand (o-CD_3OC_6H_4)_2PN(CH_3)P(o-CD_3OC_6H_4)_2 ((PNP^(OMe)_(-d)_(12)) = 1) have been prepared and characterized. A thioether analogue (o-CD_3SC_6H_4)_2PN(CH_3)P(o-CD_3SC_6H_4)_2 ((PNP^(SMe)_(-d)_(12)) = 2) and its triphenylchromium complex (PNP^(SMe))CrPh_3 (5) have also been synthesized. The solid-state structures of 4 and 7 display octahedral geometries with a κ^3-(P,P,O) coordination of PNP^(OMe) ligands having chromium−oxygen bond lengths of 2.29−2.44 A. Compound 5 differs, exhibiting (S,P,S)-κ^3 coordination of the PNP^(SMe) ligand. The deuteromethyl groups allow for ^2H NMR characterization of these paramagnetic complexes in solution. Dynamic exchange processes occur in solution at room temperature to render all four of the methoxy or thioether groups equivalent on the ^2H NMR time scale; two distinct coalescence processes are observed by variable-temperature ^2H NMR spectroscopy for all compounds. The neutral species 4 and 7 react with ethylene (1 atm) by insertion into chromium−phenyl bonds with the release of styrene and ethylbenzene, but 1-hexene is not observed under these conditions. Activation of 4 by protonation and activation of 7 by halide abstraction in the presence of ethylene provide active trimerization catalysts that give turnover numbers for 1-hexene as high as 3000 mol 1-hexene·mol^(-1) Cr. These catalysts display comparable activity and selectivity for 1-hexene compared to the original BP system, where the catalyst is generated in situ from CrCl_3(THF)_3, 1, and MAO. Both the well-defined systems and the CrCl_3(THF)_3/PNP^(OMe)/MAO system provide catalysts that undergo an initiation period followed by an apparent first-order decomposition process. Activated complexes 4 and 7 initiate trimerization primarily through ethylene insertion into the chromium−phenyl bond, followed by β-hydrogen elimination and reductive elimination to give the active species, rather than via reductive elimination of biphenyl.

MOCVD of Bismuth Oxides: Transport Properties and Deposition Mechanisms of the Bi(C6H5)3 Precursor

Deposition processes of bismuth oxides have been investigated using the Bi(C6H5)3 precursor. The role of the MOCVD parameters has been evaluated through the study of both the precursor sublimation and the entire CVD process depending on the temperature and the reactor environment. In the 350−450 °C range, Bi2O3 deposition follows a heterogeneous pathway leading to the dissociation of Bi−phenyl bonds. O2 plays a determining role in both the precursor decomposition and Bi2O3 growth. Above 450 °C, the oxidative break-down of the aromatic ring has been also observed. The temperature effect on Bi2O3 growth on platinum and iridium substrates has been investigated by grazing incident X-ray diffraction, SEM, and EDX measurements. Overall results indicate that a heterogeneous process predominantly controls the Bi2O3 deposition.

Molecular Distortion of trans-Stilbene and the Raman Intensity of the In-Phase CH Out-of-Plane Wag of the Central CHCH Group

A long-standing issue, i.e., whether the molecule of trans-stilbene is distorted around the central CC bond and/or the C−phenyl bond in solution, is examined by performing density functional calculations of the Raman intensity of the in-phase CH out-of-plane wag of the central CHCH group. Dependencies of the Raman intensity of the said mode upon the torsional angles around the central CC and C−phenyl bonds are calculated. Not only the normal species of trans-stilbene but also two isotope-labeled species, C6H513CH13CHC6H5 and C6H5CDCDC6H5, are treated. Comparisons of the calculated results with the observed spectra show that the trans-stilbene molecule is distorted in solution. The ranges of distortion around the central CC and C−phenyl bonds are estimated to be 2.5−4.0° and 8.0−12.0°, respectively, from the planar arrangement around the respective bonds.

Studies on dimerisation of tocopherols under the influence of methyl linoleate peroxides.

The stability of plant oils is related to the level of polyunsaturated fatty acids and the presence of native antioxidants--especially tocopherols. During storage, lipids or the fat products undergo oxidation and tocopherol dimers and trimers are formed. These compounds possess reducing and antioxidant properties and participate in oxidation clearly inhibiting this process. In the present study, the correlation between levels of peroxides formed during autoxidation of methyl linoleate and simultaneous decomposition of tocopherols was examined. The peroxide value was investigated. Quantities of decomposed tocopherols and formation of their dimers were determined by high-performance liquid chromatography (HPLC). Mass spectrum analysis confirmed thatthe analysed compounds were dimes. Dimerisation of gamma-T begins at the smaller quantity of the methyl linoleate peroxides than dimerisation of delta-T. At the beginning of methyl linoleate autoxidation dimerisation of gamma-T in relation to its loss was smaller. The quantity of gamma-T dimers with ether bonds in total dimers pointed to faster binding of phenoxy radicals than transformation into the phenyl ones. delta-T dimers with phenyl bonds constitute about 65% of the total. The quantity of peroxides in methyl linoleate, necessary for quantitative and qualitative changes of homologous tocopherols, decreased from delta-T to alpha-T.

Brillouin Scattering Study on o-Terphenyl Single Crystal

Elastic waves in the o-terphenyl single crystal belonging to the orthorhombic system were measured by the Brillouin light-scattering spectroscopy. Wave vectors of elastic waves were obtained from three principal values of dielectric tensor determined by a new simple method. All nine elastic constants representing elastic contribution to the free energy have been determined, which show intermediate anisotropy between benzene and linear polyphenyls. The anisotropy can reasonably be explained from the arrangement of the phenyl bonds and the inter-molecular interactions caused from the packing of molecules in the crystalline lattice. It has been found that pure transverse elastic waves would not be observed in this system by the Brillouin scattering.

Synthesis and X-ray crystal structure elucidation of an organometallic oxide containing Nb and Sn

The organometallic oxide (η 5-C 5H 5) 2Nb(Cl)(μ-O)Sn(Ph) 2Cl 2, 2, was prepared and characterized by spectroscopic methods and elemental analysis. The molecular structure was determined by X-ray crystallography. The Nb atom is in a pseudotetrahedral coordination geometry environment comprised of the two Cp rings and the chlorine and oxygen atoms. The coordination geometry around the Sn atom is a distorted trigonal bipyramidal.The determined Nb–O bond distance of 1.789(6) Å indicates a partial double bonding between Nb and O. Although the Sn–O bond can be described as a dative bond, it is a very strong interaction, 2.22(16) Å. The formation of 2 involved the activation of one of the Sn–C phenyl bonds of the tin starting material. Residual water present in the reaction solvent was the source of the bridging oxygen in the molecule.

Crystal chemistry of tetraradial species. Part 6. Embarras de richesses: lithium cation coordinated by eight O—H … phenyl bonds

Lithium tetraphenylborate tetrahydrate, [Li(OH2)4]BPh4 (LiTBw; tetragonal, I41/a, a = 27.566(2) Å, c = 12.228(2) Å, Z = 16) is remarkable in that the four H2O molecules coordinating the Li+ ion all form O—H …π hydrogen bonds to the phenyl groups of the anion. LiTBw thus appears to be the first reported example of such an exhaustive O—H …π coordination and can be described as a 3-dimensional, completely H-bonded polymer in which all the H2O hydrogens are bonded to phenyl groups and all the phenyl groups are involved in O—H … phenyl bonds. Six of the O—H … phenyl bonds are essentially normal and two are highly bent, possibly bifurcated. The existence of the H-bonds has been corroborated from variable-temperature FT-ir spectra of weakly deuterated LiTBw. The O—Li—O angles in the LiO4 coordination tetrahedron (of symmetry C1) exhibit large departures from the tetrahedral angle, two of the angles bisected by a quasi-S4 axis being 118.3° and 122.5°, respectively. An ab initio (6-31G*) investigation of the Li(OH2)4+ and Be(OH2)42+ cations has shown that such large O—M—O angles are to be expected even in the free ions and are thus not necessarily the result of packing effects. A detailed comparison with several Li(OH2)4+ and Be(OH2)42+ salts provides a rationale for the observed M(OH2)4n+ (M = Li, Be) geometries.

Complexes of the platinum metalsXLV. Synthesis and x-ray crystal structure of hexacarbonyl bis (μ- N,N′-diphenylacetamidinato)diruthenium (I/I)

The ruthenium(I) amidinato complex [Ru{PhNC(Me)NPh}(CO) 3] 2 has been prepared by heating [Ru 3(CO) 12] with the free amidine, PhNC(Me)NHPh, in boiling benzene under a carbon monoxide atmosphere, and by heating [{Ru(O 2CMe)(CO) 2} 2] n with free amidine and triethylamine in acetonitrile under carbon monoxide. The structure of [Ru{PhNC(Me)NPh}(CO) 3] 2 has been determined by X-ray diffraction methods. The binuclear complex has two Ru(CO) 3 units linked by an RuRu bond [2.714(1) Å] and a cis pair of bridging amidinato ligands. Variable temperature 1H and 13C { 1H} NMR spectra show evidence of hindered rotation about the Nphenyl bonds of the amidinate ligands. An attempt to prepare the corresponding propionamidinate derivative gave a product which is tentatively formulated as [Ru{PhNC(Et)NPh}(CO) 2(HO 2CMe)] 2 on the basis of analytical and spectroscopic evidence.

Zur Synthese des 1,2-Diphenyldecamethylcyclohexasilans

The title compound has been prepared by cyclization of 1,6-dibromo-3,4-diphenyldecamethylhexasilane with lithium. The cleavage of the siliconphenyl bonds of the cyclohexasilane by CF 3SO 3H gives the 1,2-bis-triflate derivate.