Mixture Of BF3 Research Articles

Conventional and Microwave Synthesis of 2‐Fluoro‐diazaborolidines and Their Reaction with Lithium Phosphanides

Condensation of N,N′‐disubstituted ethylenediamines with BF3·OEt2, in the presence or absence of an auxiliary base, gives mixtures of 2‐fluoro‐1,3,2‐diazaborolidines and ammonium tetrafluoroborates, respectively. Using BF3·NEt3 as the reactant allows the introduction of the boron source and the auxiliary in a single component, but suffers from the inhibition of the cyclisation by an excess of free amine formed as a by‐product. In contrast, rapid and quantitative consumption of the starting materials is observed when the reaction is carried out with a 2:1 mixture of BF3·NEt3 and BF3·OEt2 per mol of ethylenediamine at elevated temperature. Extremely short reaction times are achieved by conducting the reaction in a superheated solution in a microwave reactor. The 2‐fluoro‐1,3,2‐diazaborolidines formed under these conditions are readily isolated in high yields, and their synthetic usability is demonstrated by reactions with lithium phosphanides to give 2‐phosphanyl‐1,3,2‐diazaborolidines. Both the F‐ and R2P‐substituted N‐heterocyclic boranes are fully characterised. In addition, the structural characterisation of an unprecedented BF3 complex of Hünig's base (iPr2EtN) and of a 1,3,2‐diazaborolidine–BF3 complex is reported.

Preparation of Boron Carbide from BF3 and BCl3 in Hydrogen Plasma of Arc RF Discharge

A comparative study was carried out of the process of plasma chemical deposition of boron carbide from hydrogen plasma containing the mixtures of BF3 + CH4 and BCl3 + CH4 sustained by RF arc (13.56 MHz) discharge. It was shown that in the case of synthesis of B4C from a mixture of BF3 + CH4, carbon and complex coordination compound [X3B]−H+ (R3B·FH) are formed as the by-products of condensed products. In the case of synthesis of B4C from the BCl3 + CH4 mixture, the only condensed product is carbon. Mechanisms for the formation of boron carbide on the surface of heated electrodes are proposed. The main feature of these mechanisms is the preliminary deposition of a graphite layer from CH4 and then the precipitation of boron with the participation of the radicals BF2, BF and BCl. B4C samples were obtained and the impurity composition, morphology and structure of bulk boron carbide samples obtained using both of its halides were studied. It was found that in both cases a carbon phase is present in boron carbide samples. The main impurities entering the B4C, in the case of using a mixture of BF3 + CH4, is silicon, and in the case of a mixture of BCl3 + CH4, is tungsten.

Enantioselective Diamination with Novel Chiral Hypervalent Iodine Catalysts

Vicinal diamines constitute one the most important functional motif in organic chemistry because of its wide occurrence in a variety of biological and pharmaceutical molecules. We report an efficient metal‐free, highly stereoselective intramolecular diamination using a novel chiral hypervalent iodine reagent together with its application as an efficient catalyst for the synthesis of diamines.

Catalyst-free growth of mono- and few-atomic-layer boron nitride sheets by chemical vapordeposition

Boron nitride (BN) is a wide bandgap semiconductor with a structure analogousto graphite. Mono- and few-atomic-layer BN sheets have been grown on siliconsubstrates by microwave plasma chemical vapor deposition from a gas mixture ofBF3–H2–N2 without using any catalysts. Growth of the BN sheets can be ascribed to theetching effects of the fluorine-containing gases and the thickness control down tomono- and few-atomic-layers was realized by decreasing the concentrations ofBF3 andH2 inN2. A largedecrease of the BF3 and H2 concentrations was achieved by increasing the gas flow rate ofN2 and keepingthe BF3 and H2 flow rates constant and the mono- and few-atomic-layered BN sheets were obtained at theBF3,H2 andN2 flow rates of 3, 10, and 1200 sccm. The present mono- and few-atomic-layer BN sheetsare promising for applications in catalyst supports, composites, gas adsorption,nanoelectronics, etc.

The influence of F, F2 on kinetics of electrons in BF3

We present transport coefficients for electrons in mixtures of BF3 with its radicals (specifically F and F2) for ratios of the electric field to the gas number density E/N from 1 to 1000 Td (1 Td = 10-21 V m2). Our analysis of non-conservative collisions revealed a range of E/N where electron attachment to radicals significantly changes the electron kinetics compared to pure gaseous BF3. The results were obtained using simple solutions for Boltzmann?s equation and Monte Carlo simulation.

ChemInform Abstract: Mild Conditions for the Preparation of High-Mannose Oligosaccharide Oxazolines: Entry Point for β-Glycoside and Neoglycoprotein Syntheses.

Abstract An equimolar mixture of BF3:OEt2 and TMSBr was found to be an excellent promoter for the formation of 1,2-beta-oxazolines from peracetate derivatives of the acid-labile high-mannose oligosaccharides Man6-8GlcNAc. The oxazolines are accessible from both beta and alpha anomers of the starting oligosaccharide peracetate, and are valuable precursors for the subsequent synthesis of structurally complex glycoconjugates.

Characteristics of pulsed plasma doping sources for ultrashallow junction formation

Plasma doping of semiconductors is being investigated for low energy ion implantation to form ultrashallow junctions. In plasma doping, ions are extracted from a quasicontinuous plasma using a pulsed bias on the substrate. Plasma-based implantation techniques have the potential for higher throughput than those attainable with conventional accelerator beamlines due to the higher current densities possible with plasma sources. In this work, results from a computational investigation of plasma sources for doping of semiconductors will be discussed. An inductively coupled plasma (ICP) was used to generate ions at pressures of a few to tens of millitorr. A pulsed bias up to −20kV having lengths of tens of microseconds was applied to the substrate to accelerate the ions. Results are presented for Ar∕NF3 gas mixtures which serve as surrogates for the Ar∕BF3 mixtures that would provide boron doping. The consequences of bias voltage waveform, ICP power, operating pressure, and aspect ratio of the reactor on discharge characteristics and ion energy and angular distributions (IEADs) to the substrate will be discussed. The shape of the bias waveform has important consequences on the IEADs not only because of the transit times of the ions but also due to the instabilities that may be launched into the plasma. The aspect ratio of the reactor influences the angular uniformity of the IEADs, particularly when using large biases.

Kinetic and Surface Mechanisms to Growth of Hexagonal Boron Nitride

ABSTRACTA mechanism is presented for the gas-phase chemistry and surface reactions describing the growth of boron nitride films. The gas phase mechanism includes 33 species and 216 elementary reactions. Rate parameters for 117 elementary reactions were obtained from published experimental/theoretical data and those for the other 99 were determined using transition state theory. The mechanism examined here is an extension and update of a previous mechanism that contained 26 species and 67 elementary reactions. Standard reaction flux/pathway and gradient sensitivity analysis techniques are used to identify important reaction pathways. The calculations were handled through the use of the ChemKin software package. The model was applied to the growth of hexagonal boron nitride in an arcjet plasma source operating on mixture of BF3, H2 and N2. From the growth rate and experimental conditions for such reactors, this work demonstrates that species with mole fractions in the range of 1 × 10-10 − 2 × 10-4 (easily generated by gas-phase conditions) can account for the measured growth rate. A comparison of the predicted mole fractions of the gas-phase species present for the experimental residence times with those required to account for the measured film growth rates allows us to identify possible growth precursors. At the experimental settings, it is found that the residence time of the reacting species does not allow the flow to reach the chemical equilibrium, and that many radicals other than the source gases can account for the measured BN growth rate. The gas-phase is shown to be removed from thermodynamic equilibrium. For comparison, the equilibrium mole fractions were also calculated using an available equilibrium chemistry solver, STANJAN. Growth rates of 10-9 to 10-6 kg m-1 s-1 were measured for a wide range of H2, BF3 and NF3 flux. Both the finite-rate kinetics and equilibrium calculations confirm the importance of added hydrogen to facilitate boron nitride condensation from the gas phase. A simple surface mechanism with 7 steps is proposed with rate constants chosen to best fit the experimental growth kinetics. The results of the model, with surface rate coefficients determined from analogous gas-phase reactions, tuned slightly to agree with the experimental growth rates for BFx, x = 1, 2 or 3, as the rate-limiting growth precursor. It is also shown that the hydrogen atom has a great influence in the growth rate and that fluorine atom etches the hBN films.

Ab Initio and Cryospectroscopic Investigation of the Van der Waals Complexes of Methylcyclopropane with Hydrogen Chloride and Boron Trifluoride

The mid infrared spectra of methylcyclopropane−HCl and methylcyclopropane−BF3 mixtures, dissolved in liquid argon (LAr) or liquid nitrogen (LN2), have been examined. In LAr solutions, evidence was found for the formation of two different isomers of the 1:1 van der Waals complexesan asymmetric complex, in which the electron acceptor interacts with the C−C bond adjacent to the methyl group, and a symmetric complex in which the interaction occurs with the opposite C−C bond. At higher concentrations, indications were found for the formation of a chain-type 1:2 complex. In LN2 solutions, only the two 1:1 isomers of the HCl complex have been observed. Using spectra recorded at different temperatures, the complexation enthalpy ΔH° in LAr was determined to be −9.5(4) and −8.3(3) kJ mol-1 for the symmetric and asymmetric MCP·HCl complexes, and −9.1(2) and −6.7(5) kJ mol-1 for the symmetric and asymmetric MCP·BF3 complexes, respectively. In addition, for all investigated species, full MP2/6-31+G(d,p) geometry optim...

Infrared diode laser and microwave spectra and molecular structure of an unstable molecule, FBO

The FBO molecule was generated by a dc discharge in a mixture of BF3, O2, and He and its vibration–rotation and rotation spectra were observed by using infrared diode laser spectroscopy and microwave spectroscopy, respectively. The ν1 B–O stretching mode of F11BO and F10BO and the ν1+ν2−ν2 hot band of F11BO were observed in the region 2050 to 2140 cm−1. Subsequently, the pure rotational spectrum was observed for the following isotopic species: F11BO, F10BO, F11B18O, and F10B18O. The rotational, centrifugal distortion, and l-type doubling constants were determined from the observed spectra, and the partial rs structure of FBO was calculated from rs coordinates and the first moment equation to be r(F–B)=1.2833(7) Å and r(B–O)=1.2072(7) Å.

The microwave spectrum of the HBF+ ion

Rotational transitions of the HBF+ ion were observed in the region up to 380 GHz by using a source-modulated microwave spectrometer combined with a hollow cathode free space cell. The HBF+ (or DBF+) ion was generated by a dc discharge in a mixture of BF3 and H2 (or D2). The ion was identified on the basis of the linear-molecule spectral pattern with the nuclear hyperfine structure of the boron nucleus, supported by the spectral-intensity lowering by an external magnetic field. The rotational constant, the centrifugal distortion constant, and the nuclear quadrupole coupling constant were precisely determined for three isotopic species: H11BF+, H10BF+, and D11BF+. From the observed ground-state rotational constants the combined rs parameters were obtained; rs(BH) =1.173 47(2) Å and rs(BF) =1.210 28(2) Å.

Carbonylation of olefins and alcohols at atmospheric pressure in the presence of acid catalysts with added Ag2O or Cu2O

1. The addition of Ag2O, Cu2O, Fe, and Rh at 0.02 mole% to the acid catalysts H2SO4, (BF3·H2O)·(BF3·H3PO4), and a 3∶1 mixture of BF3·2CH2ClCOOH+BF3·2CH3COOH in the carbonylation of olefins and alcohols increased the conversion of them into carboxylic acids (3–8 times). 2. On multiple use of the studied catalytic systems in the carbonylation of olefins and alcohols a fall in their activity was observed. 3. To achieve a high (∿70%) yield of carboxylic acids in the carbonylation of olefins and alcohols with carbon monoxide at atmospheric pressure, the presence of acid catalysts with a Hammett acidity value Ho⩾−7.0 is necessary in addition to Cu2O and Ag2O activating CO.

Separation of Boron Isotopes. IV. The Methyl Sulfide-BF3 System

The exchange of boron between BF3 (gas) and the dimethyl sulfide-BF3 complex (liq.) was studied from —20°C to +26°C. The single stage separation factor changed from 1.056 to 1.031 over this temperature range with B10 concentrating in the liquid phase. Vapor pressures of dimethyl sulfide and of various mixtures of BF3 and dimethyl sulfide were determined. ΔH for the reaction BF3 (gas)+Me2S (liq.)→BF3·Me2S (liq.) was estimated to be —10.1 kcal/mole over the above temperature range. The melting point of the 1:1 complex was —19.6°C.