Showing papers on "Diborane published in 2009"

Low-Temperature Synthesis of LiBH4 by Gas–Solid Reaction

Abstract: The solvent-free synthesis of LiBH(4) from LiH in a borane atmosphere at 120 degrees C and ambient pressures is demonstrated. The source of borane is a milled LiBH(4)/ZnCl(2) mixture, in which Zn(BH(4))(2) is generated by a metathesis reaction. The yield of the reaction of about 74 % LiBH(4) shows that a bulk reaction is taking place upon borane absorption by LiH. This indicates that the formation of B-H bonds is the limiting step for the formation of LiBH(4) from the elements. Therefore, the use of diborane as a starting reactant allows one to circumvent the reaction barrier for the B-B bond dissociation and explains the rather moderate synthesis conditions.

The effect of the NH2 substituent on NH3: hydrazine as an alternative for ammonia in hydrogen release in the presence of boranes and alanes.

Abstract: Potential energy surfaces for H2 release from hydrazine interacting with borane, alane, diborane, dialane and borane–alane were constructed from MP2/aVTZ geometries and zero point energies with single point energies at the CCSD(T)/aug-cc-pVTZ level. With one borane or alane molecule, the energy barrier for H2-loss of ∼38 or 30 kcal mol−1 does not compete with the B–N or Al–N bond cleavage (∼30 or ∼28 kcal mol−1). The second borane or alane molecule can play the role of a bifunctional catalyst. The barrier energy for H2-elimination is reduced from 38 to 23 kcal mol−1, or 30 to 20 kcal mol−1 in the presence of diborane or dialane, respectively. The mixed borane–alane dimer reduces the barrier energy for H2 release from hydrazine to ∼17 kcal mol−1. A systematic comparison with the reaction pathways from ammonia borane shows that hydrazine could be an alternative for ammonia in producing borane amine derivatives. The results show a significant effect of the NH2 substituent on the relevant thermodynamics. The B–N dative bond energy of 31 kcal mol−1 in NH2NH2BH3 is ∼5 kcal mol−1 larger than that of the parent BH3NH3. The higher thermodynamic stability could allow hydrazine–borane to be used as a material for certain energetic H2 storage applications.

Catalyst-Free Synthesis and Characterization of Metastable Boron Carbide Nanowires

Abstract: Catalyst-free growth of boron carbide nanowires is achieved by pyrolysis of diborane and methane at 650–750 °C and around 500 mTorr in a quartz tube furnace. Electron-diffraction analysis using a novel diffraction-scanning transmission electron microscopy (D-STEM) technique indicates that the crystalline nanowires are single-crystal orthorhombic boron carbide. TEM images show that the nanowires are covered by a 1–3 nm thick amorphous layer of carbon. Elemental analysis by electron energy loss spectroscopy (EELS) shows only boron and carbon while energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) show the presence of oxygen as well as boron and carbon.

Characterization of electron-deficient chemical bonding of diborane with attosecond electron wavepacket dynamics and laser response

Abstract: We report a theoretical study of non-adiabatic electrons–nuclei coupled dynamics of diborane H 2 BH 2 BH 2 under several types of short pulse lasers. This molecule is known to have particularly interesting geometrical and electronic structures, which originate from the electron-deficient chemical bondings. We revisit the chemical bonding of diborane from the view point of electron wavepacket dynamics coupled with nuclear motions, and attempt to probe the characteristics of it by examining its response to intense laser fields. We study in the following three aspects, (i) bond formation of diborane by collision between two monoboranes, (ii) attosecond electron wavepacket dynamics in the ground state and first excited state by circularly polarized laser pulse, and (iii) induced fragmentation back to monoborane molecules by linearly polarized laser. The wave lengths of two types of laser field employed are 200 nm (in UV range) and 800 nm (in IR range), and we track the dynamics from hundreds of attoseconds up to few tens of femtoseconds. To this end, we apply the ab initio semiclassical Ehrenfest theory, into which the classical vector potential of a laser field is introduced. Basic features of the non-adiabatic response of electrons to the laser fields is elucidated in this scheme. To analyze the electronic wavepackets thus obtained, we figure out bond order density that is a spatial distribution of the bond order and bond order flux density arising only from the bonding regions, and so on. Main findings in this work are: (i) dimerization of monoboranes to diborane is so efficient that even intense laser is hard to prevent it; (ii) collective motions of electron flux emerge in the central BHHB bonding area in response to the circularly polarized laser fields; (iii) laser polarization with the direction of central two BH bonding vector is efficient for the cleavage of BH 3 –BH 3 ; and (iv) nuclear derivative coupling plays a critical role in the field induced fragmentation dynamics.

Pressure-induced transformations in diborane: a Raman spectroscopic study.

Abstract: As a classical electron-deficient molecule with unique hydrogen bridge bonding, diborane has created considerable interest in the structural chemistry. We report here the first evidence of pressure-induced structural transformations of diborane probed by in situ Raman spectroscopy. At pressures around 4 GPa, diborane undergoes a liquid-solid phase transformation to a new high-pressure phase I with a possible structure similar to the low-temperature phase. When compressed to above 6 GPa, the spectral features, such as doubling of the lattice modes, appearance of several new internal modes, and emergence of a new ring stretch mode, indicate the structural transformation to another new high-pressure phase II. This phase has a possible extended network structure of higher hydrides of borane. At pressures above 14 GPa, diborane transforms to yet another high-pressure phase III. All of the observed pressure-induced structural transformations are completely reversible upon decompression.

1,1- and 1,2-isomers of the diborane(4) compound B2{1,2-(NH)2C6H4}2 and a TCNQ Co-crystal of the 1,1-isomer

Abstract: The synthesis and X-ray crystal structures of the diborane(4) isomers 1,1-B2{1,2-(NH)2C6H4}2 and 1,2-B2{1,2-(NH)2C6H4}2 are described together with the results of quantum chemical calculations which shed light on their relative stabilities and degree of aromaticity. Spectroscopic data are also provided for both isomers of the 4-methyl aryl derivative. The compound 1,1-B2{1-O-2-(NH)C6H4}2 has also been prepared and structurally characterised but no evidence was obtained for the corresponding 1,2-isomer. The compound 1,1-B2{1,2-(NH)2C6H4}2 forms a co-crystal with TCNQ, the structure of which is also reported.

In situ high-pressure study of diborane by infrared spectroscopy.

Abstract: As the simplest stable boron hydride in its condensed phase, diborane exhibits an interesting structural chemistry with uniquely bridged hydrogen bonds. Here we report the first room-temperature infrared (IR) absorption spectra of solid diborane compressed to pressures as high as 50 GPa using a diamond anvil cell. At room temperature and 3.5 GPa, the IR spectrum of diborane displays rich sharply resolved fundamentals and overtones of the IR active bands, consistent with the previous low-temperature IR measurements of condensed diborane at ambient pressure. When compressed stepwise to 50 GPa, several structural transformations can be identified at pressures of ∼3.5 GPa, ∼6.9 GPa and ∼14.7 GPa, as indicated by the changes in the band profile as well as the pressure dependence of the characteristic IR modes and bandwidths. These transformations can be interpreted as being enhanced intermolecular interactions resulting from compression. The geometry of the four-member ring of B2H6, however, does not seem to b...

1,1'-Diborylferrocenes from [2]Boraferrocenophanes by Boron-Boron Exchange

Abstract: The reactivity of [2]boraferrocenophane [(η5-C5H4)–BNMe2–BNMe2–(η5-C5H4)Fe] (3) with borane and diborane compounds was examined, resulting in the complete loss of the–BNMe2–BNMe2– bridge and the concomitant formation of 1,1′-borylated ferrocenes. With this unprecedented reactivity pattern, an alternative access to this class of compounds is established.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Difluorenyl[2]borametallocenophanes of Group 4 Metals: Synthesis and Structure

Abstract: We report the synthesis of difluorenyl[2]borametallocenophanes of Zr and Hf. The ligand precursor has been synthesized starting from 1,2-dibromo-1,2-bis(dimethylamino)diborane(4) upon reaction with Li[C 13 H 9 ]. All compounds have been fully characterized by multinuclear NMR spectroscopy and, in addition, selected examples by X-ray analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Winheim, Germany, 2009).

Synthesis of crystalline boron nanoribbons and calcium hexaboride nanowires by low pressure chemical vapor deposition

Abstract: Low pressure chemical vapor deposition was used to synthesize crystalline boron nanoribbons of 16 nm thickness by both uncatalyzed and nickel-catalyzed pyrolysis of diborane at relatively low temperatures. The nanoribbons were characterized with scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Auger electron spectroscopy, and Raman spectroscopy. Similar procedures were used to synthesize and characterize calcium hexaboride nanowires. The nanostructures reported here are compared with recent literature results for boron nanoribbons and CaB6 nanowires grown by the same method.

Hydrogen storage materials containing ammonia borane

Abstract: According to at least one aspect of the present invention, an ammonia borane containing hydrogen storage material is provided to be present with substantially reduced formation of borazine or diborane. In at least one embodiment, the hydrogen storage material includes at least one ammonia borane (NH3BH3); and at least one amide of the formula M(NH2)x, wherein M is a cationic element or a combination of two or more cationic elements from groups 1 to 14 of the periodic table and x represents a total cationic charge to charge balance M.

Single Crystal Boron-Doped Diamond Synthesis

Abstract: The electrical characteristics of high quality single crystal boron-doped diamond are studied. Samples are synthesized in a high power-density microwave plasma-assisted chemical vapor deposition (CVD) reactor at pressures of 130-160 Torr. The boron-doped diamond films are grown using diborane in the feedgas at concentrations of 1 to 50 ppm. The boron acceptor concentration is investigated using infrared absorption and a four point probe is used to study the conductivity. The temperature dependent conductivity is analyzed to determine the boron dopant activation energy.

Method for manufacturing transparent conductive oxide (tco) films; properties and applications of such films

Abstract: A method for manufacturing a boron doped, transparent, conductive zinc oxide layer from on a substrate is disclosed. The layer is being deposited from at least diethylzinc, water and diborane by low pressure chemical vapour deposition (LPCVD) in a process chamber of a deposition system comprising wherein the gas flow ratio of diethylzinc and water is kept between 0.87 and 1.3 and the gas flow ratio of diborane and diethylzinc is being kept between 0.05 and 0.4. The haze of such manufactured layer, measured as ratio of diffuse transmittance to total transmittance at 600nm, is between 10 and 25%.

Method for producing diborane

Abstract: PROBLEM TO BE SOLVED: To provide a method for producing diborane which can obtain high purity diborane in a good yield without generating methyl chloride and methane as impurities, and which can improve yield of a recyclable solvent. SOLUTION: Sodium borohydride is reacted with diborane to generate NaB 2 H 7 as a reaction intermediate. The reaction intermediate is reacted with an acid to generate diborane in an amount exceeding the amount of diborane reacting with the sodium borohydride. COPYRIGHT: (C)2011,JPO&INPIT

Plasma doping method and manufacturing method of semiconductor device

Abstract: A plasma doping method capable of introducing impurities into an object to be processed uniformly is supplied. Plasma of a diborane gas containing boron, which is a p-type impurity, and an argon gas, which is a rare gas, is generated, and no bias potential is applied to a silicon substrate. Thereby, the boron radicals in the plasma are deposited on the surface of the silicon substrate. After that, the supply of the diborane gas is stopped, and bias potential is applied to the silicon substrate. Thereby, the argon ions in the plasma are radiated onto the surface of the silicon substrate. The radiated argon ions collide with the boron radicals, and thereby boron radicals are introduced into the silicon substrate. The introduced boron radicals are activated by thermal processing, and thereby a p-type impurity diffusion layer is formed in the silicon substrate.

Process for producing 1,3,2-dioxaborinane compounds

Abstract: A process for producing a 1,3,2-dioxaborinane compound of the general formula (I) in which each R individually is selected from the group consisting of H and C 1-6 -alkyl, by reacting a diol of the general formula (II) HO-CRR-CRR-CRR-OH with diborane is performed without using a solvent.

Method and apparatus for refining crude diborane

Abstract: PROBLEM TO BE SOLVED: To provide a method and an apparatus for refining crude diborane to obtain high purity diborane by refining the crude diborane simply, inexpensively and in a high yield. SOLUTION: Gaseous crude diborane containing a plurality of impurities is in contact with a plurality of adsorbents 3a, 3b and 3c which have different adsorption performance to the impurities in order and then liquefied. The adsorbents 3a, 3b and 3c are classified according to their kinds and stored in a plurality of adsorbing tanks 4a, 4b and 4c. A plurality of the adsorbing tanks 4a, 4b and 4c storing different kinds of the adsorbents 3a, 3b and 3c are arranged in series in a diborane flow path 8 from the supplying source 2 of the crude diborane to a condenser 7. COPYRIGHT: (C)2011,JPO&INPIT

Structure and Stability of Multivalent Metal Tetraborohydrides

Abstract: Metal tetrahydroborates remain interesting materials as potential hydrogen storage media. In the present paper, we analyze thermodynamic stability of borohydrides of Al and Zr by means of extensive density functional calculations. We show that solid phases of these compounds are formed by dispersive Van der Waals forces. These compounds are thermodynamically unstable at room temperature with respect to decomposition to boron and hydrogen. Their stability is explained by formation of diborane as a necessary step in the decomposition path, pointing out to the kinetic factors that are important for the stability analysis of metal borohydrides.

Phosphine-borane compounds

Abstract: A phosphine-borane compound is represented by formula (P-1) (wherein R1 and R2 are independently H or substituted or unsubstituted hydrocarbyl; R3 is an asymmetric hydrocarbon group or an asymmetric substituted hydrocarbon group). The synthesis of (P-1) may be achieved by subjecting a hydrogen phosphine borane (P-2) to a coupling reaction with an optically active isocyanate (3). Since (P-1) may comprise diastereomers (as R1 and R2 may induce asymmetry in the phosphorus atom), optical resolution is possible (e.g. via crystallization). Decomposition of optically pure (P-1) may give optically pure (P-2). (P-1) maybe tert-butyl (methyl) [N-((S)-1-phenylethyl)carbamoyl]phosphine-borane, adamantyl(methyl) [N-((S)-1-phenylethyl)carbamoyl]phosphine-borane or 2,5-dimethyl-1-[N-((S)-1-(1-napthyl) ethyl) carbamoyl]phosphorane-borane. Optically pure (P-2) may be useful to prepare (S, S)-2,3-bis(tent-butylmethylphosphino)quinoxaline (QuinoxP (RTM)) or (R,R)-1, 2-bis(tertbutylmethylphosphino)ethane diborane (BisP* diborane).