Showing papers on "Diborane published in 1973"

Growth of boron‐doped diamond seed crystals by vapor deposition

Abstract: p‐type semiconducting diamond was grown by vapor deposition from a 0.83% diborane in methane gas mixture at 1050°C and 0.2 Torr on 0 to 1‐μ nominal size natural type‐I diamond powder. Total mass increases of about 9% were achieved which correspond to average linear growth rates of less than 10−3 μ/day. Evidence showing the growth was boron‐doped diamond included chemical etching, x‐ray and electron diffraction, density measurements, Seebeck and resistivity measurements, chemical analysis, optical measurements, induced electron emission spectroscopy, and scanning electron microscopy. The crystalline quality of the new diamond has not been established; it may be highly defective. A distinct change in color of the diamond seed crystals from an off‐white or gray for virgin crystals to light blue after growth was observed. The results are further confirmation that diamond may be grown at low pressures where it is thermodynamically metastable with respect to graphite. It is also further evidence that boron is t...

Organometallic complexes in synthesis. Part V. Some tricarbonyliron derivatives of cyclohexadienecarboxylic acids

Abstract: Reactions of iron pentacarbonyl with several methyl cyclohexadienecarboxylates lead to tricarbonyliron complexes. The most stable of these is the ‘conjugated’ isomer (2; R = Me), which can be obtained from the others by treatment with methanolic acid or in some cases with methanolic methoxide. The latter method is the first observed example of base-catalysed isomerisation in tricarbonylcyclohexadieneiron complexes. When deuteriated reagents are used the acidic procedure leads to incorporation of one deuterium atom only, in the 6-position. irrespective of the starting material. Reactions of the acids with diborane yield the carbinols, one of which [tricarbonyl-1 -(hydroxymethyl)cyclohexa-1,3-dieneiron (8)], on treatment with acid, produces the rearranged carbonium salt (9). Hydride abstraction from the isomeric esters gives a series of carbonium salts, which react with water at various rates to produce hydroxy-complexes and dimeric ethers. Complexing of some methyl methylcyclohexa-1,4-dienecarboxylates is reported. Aspects of theory connected with hydrogen migration and hydride abstraction are discussed.

Hetero-Epitaxial Growth of Lower Boron Phosphide on Silicon Substrate Using PH 3 -B 2 H 6 -H 2 System

Abstract: Single crystal of lower boron phosphide (B13P2) with hexagonal structure was obtained hetero-epitaxially on silicon substrate. Diborane (B2H6) and phosphine (PH3) diluted in hydrogen were used as reactant gases. The substrate temperatures were between 1050°C and 1250°C and the molecular ratio of reactants to carrier hydrogen was below 3.2×10-4. The epitaxial relations were: B13P2(110)/Si(100), B13P2(110)/Si(110) and B13P2(100)/Si(111). The lower boron phosphide was a transparent film and its resistivity was measured as 1×108 Ω-cm at room temperature.

Reduction of α-D-Hexopyranosulosides

Abstract: Reduction of isopropyl tri-O-acetyl-α-D-arabino-hexopyranosuloside with sodium borohydride or diborane leads almost exclusively to the gluco-configuration. Catalytic reductions, on the other hand, ...

Thermal decomposition of diborane. Part I. The decomposition mechanism at low conversion and temperature and the inhibiting effect of accumulated hydrogen

Abstract: A gas recirculating device was used to trap the condensible products at –130 °C at the exit of the reaction vessel. The reaction order was three halves in diborane concentration. The Arrhenius parameters, admittedly low, are: log A/(cm3/2 mol–1/2 s–1)= 4·72 ±0·14 and Ea= 42·47 ± 1·17 kJ mol–1. The reaction, however, is considered to be truly homogeneous since neither coating nor changes in surface:volume ratio altered the rate constant found in an aged reaction vessel. The decomposition was also studied in a static system. For reaction times shorter than 200 s a marked decrease of the rate constant with time was observed. After this interval the rate constant stabilizes and remains almost constant and the figures found are similar to those reported in previous studies. A competitive reaction between an intermediate and hydrogen (inhibition) or diborane is suggested to account for the initial decrease of the rate constant. The decomposition of products (principally B5H11) is held, responsible for the observed constancy of the rate constants after the first 10 min of reaction.

Chemistry of Diborane and Sodium Borohydride. VIII. Imidate Formation from Nitriles with Sodium Borohydride

Abstract: The reaction of heteroaromatic nitriles with trace of sodium borohydride in alcohol was examined.Cyano group substituted at α-position of heteroatoms was easily converted to the corresponding imidate.It was also possible to convert selectively one cyano group to the ester group without any change of the other cyano groups.

Chemistry of Diborane and Sodium Borohydride. X. The Reduction of 2-or 4-Substituted Pyridines and Quinolines, and 1-or 3-Substituted Isoquinolines with Sodium Borohydride

Abstract: The reaction of 2-or 4-substituted pyridines and quinolines and 1-or 3-substituted isoquinolines with sodium borohydride was examined. The substituent groups which are usually resistant to reduction with sodium borohydride were reducible through the electronic influence of the heteromatic ring. The solvent effects on the reduction with sodium borohydride were also examined.

A Diborane-Free Synthesis of μ-Dimethylaminodiborane

Abstract: Treatment of K(CH3) 2NBH3 in diglyme with a threefold excess of NaBH4 and one half mole of iodine produces a solution of Na(CH3)2N(BH3)2 which may be converted to μ-(CH3)2NB2H5 by addition of another half mole of iodine.

Stabilized borane-tetrahydrofuran solutions

Abstract: The presence of an aliphatic, alicyclic, or cyclic sulfide stabilizes solutions of diborane in tetrahydrofuran, permitting the storage of such solutions for long periods of time at ambient temperatures. Such stabilized solutions can be prepared without handling diborane gas by treating a suspension of an ionic borohydride in tetrahydrofuran, containing an aliphatic, alicyclic, or cyclic sulfide, with boron trifluoride, followed by removal of the precipitated fluoroborate. Such solutions are excellent for hydroboration, and possess major advantages over borane-tetrahydrofuran solutions available previously in being highly stable.

The reaction of t-butoxyl radicals with diborane

Abstract: The reaction of butoxyl radicals with diborane has been shown by e.s.r. spectroscopy to yield t-butyl radicals. The rate constant for this process is given by k= 108·4× 102·9/θ l mol–1 s–1 where θ= 2·303 RT in kcal mol–1. No intermediate 4-co-ordinate boron radical could be detected. Analogies are drawn with t-butoxyl–trialkyl phosphite reaction and with the oxidation of trialkylboranes by alkaline hydrogen peroxide and by amine oxides. t-Butyl radicals are not formed in detectable quantities in either the t-butoxyl–alkyldiborane or in the t-butoxyl–phosphine reactions.

Scrambling in ethane molecular ion: An INDO model for hydrogen exchange before mass spectral fragmentation

Abstract: INDO calculations for previously proposed activated complexes for scrambling in ethane molecular ion suggest that the structure equivalent to diborane is more stable than one in which hydrogens on the same side of the molecule exchange positions.

Chemistry of diborane and sodium borohydride part 9, the reduction of 3‐substituted pyridines and quinolines, and 4‐substituted isoquinolines with sodium borohydride

Abstract: Die Umsetzung von Pyridinen, Chinolinen und Isochinolinen mit Natriumbo1= hydrid ergibt die im Formelschema angegebenen Reduktionsprodukte.

Low temperature production of amorphous boron-carbon

Abstract: Process comprises placing a substrate in a vacuum chamber at =25 torr pref to about 5mm Hg abs, heating the substrate to 500-1000 degrees C, pref is approx 850 degrees C, and contacting the substrate with a gaseous mixture of acetylene and a boron hydride, especially diborane - The gas mixture pref contains in addition, hydrogen, and a particular composition in 3 pts acetylene, 2 pts hydrogen and 12 pts diborane - The substrate may be silica or glass, suitably employed as a continuous filament passing through the vacuum chamber - The amorphous deposits have high tensile strength and elastic moculus even at high temperature

Umsetzungen von metall- und metalloidverbindungen mit mehrfunktionellen molekuelen 1. mitt. die reaktion von diboran mit 2-aminobenzonitril und 2-amino-1-cyclopenten-1-carbonsaeurenitril

Abstract: The reaction of 2-aminobenzonitrile with diborane yielded 2-cyano-phenylamine-borane, bis(2-cyanophenylamino)borane, 2.3′-bis(1.3.2-diazabora-3.4-dihydronaphthalene) and at elevated temperatures 5,8.13.16.21.24-hexahydro-borazino[2.1-b: 4.3-b′:6.5-b″]tris[1.3.2]diazaboranaphthalene. This borazine compound and 2.3′-bis(1.3.2-diazaboradihydronaphthalene) were also obtained from 2-aminobenzylamine-borane.