Synthesis and some properties of silanes and siloxanes with 5,5,6,6,7,7,7-heptafluoro-4,4-bis(trifluoromethyl)heptyl substituents

Methods for syntheses of new polyfluorinated compounds, viz., silanes containing substituents CF₃CF₂CF₂C(CF₃)₂(CH₂)₃ (R^F) at the silicon atom and 1,3,5-tris(R^F)-1,3,5-trimethylcyclotrisiloxane that can be used for the synthesis of fluorocontaining oligo- and polysiloxanes of different structure, were developed. The polymerization of cyclotrisiloxane in the presence of 1,3-divinyltetramethyldisiloxane gave linear oligomers, whose chain contain -(R^F)Si(Me)O- units.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2133–2136, October, 2004.     

Phenyl(acyloxy)fluorosilanes C6H5Si(OCOR)nF3?n (n = 1, 2) and phenyl(acyloxy)fluorochlorosilanes C6H5Si(OCOR)FCl

The method of synthesis of the hitherto unknown class of organosilicon compounds, phenyl(acyloxy)fluorosilanes C₆H₅Si(OCOR) _n F_3−n (n = 1, 2) and phenyl(acyloxy)fluorochlorosilanes C₆H₅Si(OCOR) FCl in up to 91% yield has been developed based on the reaction of phenyl(fluoro)chlorosilanes C₆H₅SiCl _n F_3−n (n = 1, 2) with trimethylsilyl esters of carboxylic acids Me₃SiOC(O)R [R = H, CH₃, CF₃, CCl₃, ClCH₂, BrCH₂, CH₂=CHCH₃, CH₂=CHPh, CH(CH₃)=CH₂, Ph].     

Phenylhalosilazanes

A method of synthesis of phenylhalosilazanes by the reaction of phenyl(fluoro)chlorosilanes PhSiF_3–n Cl _n (n = 0–3) with hexamethyldisilazane at room temperature is elaborated. The thermolysis of 1,1,1-trimethyl-3-phenyl-3,3-difluorodisilazane affords cyclic phenylfluorosilazanes (PhSiFNHSiMe₃)n (n = 3–5). The process may occur via the intermediate formation of phenylfluorosilimine.     

Effect of the temperature on the composition and ratio of hydrolysis products of 1,2-dichlorotetramethyldisilane

The hydrolysis of 1,2-dichlorotetramethyldisilane was studied at different temperatures. At reduced temperatures, the hydrolysis gave permethylcyclo(oxadisilanes) [(Me₂Si)₂O]_n (n = 2 and 3) and α,ω-dihydroxypermethyloligo(oxadisilanes) HO[(SiMe₂)₂O]_mH (m = 1–5). The formation of the latter was proved by the GC-MS method. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 722–724, April, 2006.     

Radiation telomerization of tetrafluoroethylene in butyl chloride solution

The kinetics of the radiation-initiated polymerization of tetrafluoroethylene (TFE) in butyl chloride has been studied. The rate of the process, the properties and yield of telomers obtained depend on the initial concentration of TFE (2.6–22 wt %) in the solution and the dose of γ-irradiation. The analysis of the measured IR absorption spectra and a possible scheme of the process allow to suggest that the main product of the reaction is C₄H₈Cl(C₂F₄) _n−1CF₂CF₂H with the formation of small amounts of C₄H₉(C₂F₄) _n−1CF₂CF₂H and Cl(C₂F₄) _n−1CF₂CF₂H. The average number of links in the telomer (n) increases from 7.6 to 16.1 when the concentration of the monomer in the solution varies in the range of 7–22 wt %. The length of the chain of the soluble telomers (n) does not depend on the initial concentration of TFE and makes ∼7.     

Surface Modification of Silicone Rubber by CF<Subscript>4</Subscript> Radio Frequency Plasma Immersion

Silicone rubber samples were treated by CF₄ capacitively coupled plasma at radio frequency (RF) power of 60, 100 and 200 W for a treatment time up to 20 min under CF₄ flow rate of 20 sccm, respectively. Static contact angle, ATR-FTIR and XPS, and AFM were employed to characterize the changes of surface on hydrophobicity, functional groups, and topography. The results indicate the static contact angle is improved from 100.7 to 150.2°, and the super-hydrophobic surface, which corresponds to a static contact angle of 150.2°, appears at RF power of 200 W for a 5 min treatment time. It is suggested that the formation of super-hydrophobic surface is ascribed to the co-action of the increase of surface roughness created by the ablation reaction of CF₄ plasma and the formation of [–SiF _x (CH₃)_2−x –O–] _n (x = 1, 2) structure produced by the direct attachment of F atoms to Si.     

Geometrical structures and possible dissociation channels of MnP n + (n = 2–8) binary cluster ions

An all-electron (AE) calculation on the geometrical structures and possible dissociation channels of MnP _n ⁺ (n = 2–8) cluster ions has been performed by using density functional theory with the generalized gradient approximation (GGA) at PW91 level. The lowest energy structures of MnP _n ⁺ (n = 2–8) cluster ions may be regarded as the outcome of bonding between Mn atom and one or two units of P₂, P₃, and P₄. The most possible dissociation channels of MnP _n ⁺ (n = 2–8) cluster ions are the detachment of P₂, P₃, or P₄ unit. These conclusions are basically consistent well with previous works in which the P₂ and P₄ structures are regarded as two relatively stable units and easy to be stripped.     

Synthesis and Electrochemical Behavior of Some 1H-3-Methyl-4-ethoxycarbonyl-5-(benzylidenehydrazino)pyrazoles

1H-3-Methyl-4-ethoxycarbonyl-5-(benzylidenehydrazino)pyrazoles are key intermediates in obtaining various heterocyclic systems including pyrazolotriazoles. We present the voltammetric behavior of these compounds in nonaqueous media, with the following para substituents grafted on the benzene ring: –N(CH₃)₂, –OH, –OCH₃, –F, –Cl, –CF₃, –NO₂, as well as of the novel compounds with –Br, –I, and –SCH₃ in the para position, in order to elucidate the influence of the various substituents on the mechanism of anodic oxidation.     

Synthesis and Electrochemical Behavior of Some 1H-3-Methyl-4-ethoxycarbonyl-5-(benzylidenehydrazino)pyrazoles

Summary. 1H-3-Methyl-4-ethoxycarbonyl-5-(benzylidenehydrazino)pyrazoles are key intermediates in obtaining various heterocyclic systems including pyrazolotriazoles. We present the voltammetric behavior of these compounds in nonaqueous media, with the following para substituents grafted on the benzene ring: –N(CH₃)₂, –OH, –OCH₃, –F, –Cl, –CF₃, –NO₂, as well as of the novel compounds with –Br, –I, and –SCH₃ in the para position, in order to elucidate the influence of the various substituents on the mechanism of anodic oxidation.     

A novel series of nickel(II)-dppe-arylazoimidazole complexes. Synthesis and spectroscopic characterization

Reaction of [Ni(dppe)Cl₂/Br₂] with AgOTf in CH₂Cl₂ medium following ligand addition leads to [Ni(dppe)(OSO₂CF₃)₂] and then [Ni(dppe)(RaaiR)](OSO₂CF₃)₂ [RaaiR′ = p–R–C₆H₄–N=N–C₃H₂–NN-1–R′,(1–3), abbreviated as N,N′-chelator, where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), Me (b), Cl (c) and R′ = Me (1), CH₂CH₃ (2), CH₂Ph (3), OSO₂CF₃ is the triflate anion]. ³¹P{¹H}-NMR confirm that stable bis-chelated square planar Ni(II) azoimine–dppe complex formation with one sharp peaks. The ¹H NMR spectral measurements suggest azoimine link is present with lot of phenyl protons in the aromatic region. Considering all the moities there are a lot of different carbon atoms in the molecule which gives many different peaks in the ¹³C(¹H)-NMR spectrum. In the ¹H-¹H COSY spectrum in the present complexes and contour peaks in the ¹H-¹³C-HMQC spectrum in the present complexes, assign the solution structure and stereoretentive conformation in each complexes.     

Radiation telomerization of tetrafluoroethylene in tetrahydrofuran

According to DSC, DTG, and GPC data, H(CF₂CF₂)nC₄H₇O telomers with a chain length of n = 1−4 and T _b ≈ 170−200°C were formed during the radiolysis of a binary mixture of tetrafluoroethylene + tetrahydrofuran in a molar ratio of (0.37–2)/1 between the reactants at room temperature. IR spectroscopy and quantum-chemical calculations demonstrated that telomerization occurred with chain transfer through the α-hydrogen of the furan ring.     

New one-step methods for the synthesis of the metallonium dication [Ru(η5-C5Me5)(η5:σ:σ-C5Me3(CH2)2]2+ and its heteroannular analog starting from decamethylruthenoceneand its heteroannular analog starting from decamethylruthenocene

The reaction of decamethylruthenocene with oleum or with an oleum—acid (CF₃SO₃H or CF₃CO₂H) mixture as well as UV photolysis of a Cp^* ₂Ru solution in CF₃SO₃H in the presence of a small amount of oleum afforded two metallonium dications,viz., [Ru(η⁵-C₅Me₅)(η⁵:σ:σ-C₅Me₃(CH₂)₂]²⁺ and [Ru(H₂)(η⁵:σ:-C₅Me₄CH₂)₂]²⁺. The structures of these dications were confirmed by the results of their alkaline hydrolysis and NMR spectra. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 517–522, March, 2000.     

A novel series of gold(III)-bis-triphenylphosphine-arylazoimidazole complexes: synthesis and spectroscopic and redox study

Reaction of [Au(PPh₃)₂(tht)₂](OSO₂CF₃)₃ with RaaiR′ in CH₂Cl₂ medium following ligand addition leads to [Au(PPh₃)₂(RaaiR′)](OTf)₃ [RaaiR′ = p-R–C₆H₄–N=N–C₃H₂–NN–1–R′, (1–3), abbreviated as N,N′-chelator, where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), Me (b), Cl (c) and R′ = Me (1), CH₂CH₃ (2), CH₂Ph (3), PPh₃ is triphenylphosphine, OSO₂CF₃ is the triflate anion, tht is tetrahydrothiophen]. The maximum molecular peak of the corresponding molecule is observed in the ESI mass spectrum. The ¹H-nmr spectral measurements suggest methylene, –CH₂–, in RaaiEt gives a complex AB type multiplet while in RaaiCH₂Ph it shows AB type quartets. ¹³C-nmr spectrum suggests the molecular skeleton. In the ¹H–¹H COSY spectrum as well as contour peaks in the ¹H–¹³C heteronuclear multiple-quantum coherence (HMQC) spectrum assign the solution structure. Electrochemistry assign ligand reduction part rather than metal oxidation.     

An in-depth in situ IR study of the thermal decomposition of yttrium trifluoroacetate hydrate

The pyrolysis of Y(CF₃COO)₃·nH₂O at temperatures up to 1,000 °C, under flowing pure Ar, O₂ and O₂ saturated with water vapour, was extensively analysed. The formation of HF is observed directly and the existence of a :CF₂ diradical is inferred during a trifluoroacetic acid salt decomposition. High resolution thermogravimetry, differential scanning calorimetry, X-ray diffractometry and scanning electron microscopy indicated that the exothermic one-stage decomposition of the anhydrate salt occurs at 267 °C, forming YF₃. Fourier transform infrared spectroscopy identified (CF₃CO)₂O, CF₃COF, COF₂, CO₂ and CO as the principal volatile species; and revealed the influence of water on the reactions liberating gaseous CF₃COOH, CHF₃, HF, and SiF₄ (from reactions with glass or quartz components). NO₂ and N₂O evolution suggested that traces of CH₃NO₂ were present in the starting material. Thermogravimetry and X-ray diffractometry indicated that the slow hydrolysis of the fluoride occurs between 630 and 655 °C, forming a mixture of Y₂O₃, YOF, Y₇O₆F₉, and YF₃. The decomposition and hydrolysis temperatures are significantly lower than previously reported, which has implications for sol–gel processing.     

ESR study of radicals formed by the reduction of α-diketones C(O)C(O)CF3 (R=(CF3)2CF, C6F5, (CF3)3C) with several group I–III metals

The ESR spectra of radical anions formed by reduction of α-diketones RC(O)C(O)CF₃ (R=(CF₃)₂CF, C₆F₅, (CF₃)₃C) with metals (Li, Na, K, Mg, Cd, Zn, Hg, In, and TI) in THF were studied. For R=(CF₃)₂CF and C₆F₅, the radical anions are formed ascis-isomers, whereas for R=(CF₃)₃C,trans-isomers are obtained. Line broadening due to solvation and desolvation of the cation is observed in the latter case. The reduction of α-diketone (CF₃)₂CFC(O)C(O)CF₃ with Group II metals (Mg, Cd, Zn) results in the formation of radical pairs. Translated fromIzvestiya Akadmii Nauk. Seriya Khimicheskaya, No. 11, pp. 2228–2231, November, 1998.     

The effects of the solvent and the ligand chirality on the regioselectivity of alkene oxidative esterification by PdII carboxylates

The effects of the solvent and the ligand chirality on the regioselectivity of oxidative esterification of propylene and cyclohexene by Pd^II carboxylates were studied using achiral (MeCO₂ ⁻, Me₂CHCH₂CO₂ ⁻), racemic ((±)-CF₃CF₂CF₂OC^*F(CF₃)CO₂ ⁻), and chiral ((S)−(+)−MeC^*H(Et)CO₂ ⁻, (+)−CF₃CF₂CF₂OC^*F(CF₃)CO₂ ⁻) carboxylate ligands. The oxidation of alkenes in aprotic media (CHCl₃, CH₂Cl₂, CO₂, THF) affords mainly allylic esters (in the case of cyclohexene also homoallylic esters) and the oxidative esterification at the vinylic position is absent. In weakly solvating media (CHCl₃, CH₂Cl₂) the regioselectivity of cyclohexene oxidation (the allyl to homoallyl ratio) increases substantially on going from achiral or racemic acido ligands to chiral acido ligands. In a more donor medium (THF) the ligand chirality effect almost vanishes. The effects of the ligand chirality and the nature of the solvent on the mechanism of alkene oxidation by Pd^II complexes are discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1695–1703, September, 1999.     

Theoretical studies on anionic clusters of sulfate anions and carbon dioxide, SO 4?1/?2 (CO2)n, n?=?1?4

Geometry optimizations were performed on monoanionic and dianionic clusters of sulfate anions with carbon dioxide, SO₄^−1/−2(CO₂) _n , for n = 1–4, using the B3PW91 density functional method with the 6-311 + G(3df) basis set. Limited calculations were carried out with the CCSD(T) and MP2 methods. Binding energies, as well as adiabatic and vertical electron detachment energies, were calculated. No covalent bonding is seen for monoanionic clusters, with O₃SO–CO₂ bond distances between 2.8 and 3.0 ?. Dianionic clusters show covalent bonding of type [O₃S–O–CO₂]⁻², [O₃S–O–C(O)O–CO₂]⁻², and [O₂C–O–S(O₂)–O–CO₂]⁻², where one or two oxygens of SO₄⁻² are shared with CO₂. Starting with n = 2, the dianionic clusters become adiabatically more stable than the corresponding monoanionic ones. Comparison with SO₄^−1/−2(SO₂) _n and CO₃^−1/−2(SO₂) _n clusters, the binding energies are smaller for the present SO₄^−1/−2(CO₂) _n systems, while stabilization of the dianion occurs at n = 2 for both SO₄⁻²(CO₂) _n and SO₄⁻²(SO₂) _n , but only at n = 3 for CO₃⁻²(SO₂) _n .     

Synthesis of α,ω-dihalopermethyloligosilanes and silane-siloxane copolymers

α,ω-Dibromopermethyloligosilanes, Br(SiMe₂) _n Br (n=2–4, 6), were prepared by the reaction of dodecamethylcyclohexasilane with bromine. The reaction of (Me₂Si)₆ with MCl₄ (M=Sn, Ti) proceeds with the cleavage of Si−Si- and Si−C-bonds with the formation of α,ω-dichloropermethyloligosilanes, Cl(SiMe₂) _n Cl (n=2–4, 6), and chloro derivatives of cyclohexasilane, Cl _m Si₆Me_12−m (m=1, 2). Silane-siloxane copolymers of regular structure were obtained by heterofunctional copolycondensation of α,ω-dihalopermethyloligosilanes with 1,5-dihydroxyhexamethyltrisiloxane. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1513–1517, August, 1997.     

Conformation of perfluoroalkyl radicals in the solid phase

An equilibrium conformation of the perfluoroalkyl ∼CF₂·CF₂ radical at 77 K in matrices of polytetrafluoroethylene andn-perfluoroalkanes was studied. Upon cooling from 300 to 77 K at temperatures below 200 K, the ESR spectrum of this radical changes, and the well-resolved hyperfine structure appears. The hyperfine splitting constants on nuclei of two nonequivalent F_β atoms were determined: 2.2 and 1.1 mT, respectively. TheA _∥ andA _⊥ values for the F_α atoms are 22.5 and 3.3 mT, respectively. The conformational angle between the axis of the orbital of an unpaired electron and projection of the C_β−C_γ bond is 5.6°. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 331–334, February, 1999.     

Endohedral gadolinium-containing metallofullerenes in the trifluoromethylation reaction

An efficient method for the synthesis of trifluoromethyl derivatives of endohedral gadolinium-containing metallofullerenes was proposed. High-purity (98–99%) trifluoromethyl derivatives Gd@C₈₂(CF₃)₅ (two isomers) and Gd₂@C₈₀(CF₃) have been synthesized for the first time. They were isolated and characterized by HPLC, MALDI-TOF mass spectrometry, and UV-Vis spectroscopy. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1457–1462, July, 2008.