Showing papers on "Nickel boride published in 2002"

Synthesis and XPS Characterization of Nickel Boride Nanoparticles

Abstract: Functionalized AOT reverse micelles (Ni(AOT)2/Na(AOT)) were used in an attempt to form nickel metal nanoparticles. After reduction by sodium borohydride either under nitrogen or in open air, nanoparticles are obtained. However, it is shown by X-ray photoelectron spectroscopy analysis that Ni2B is obtained under nitrogen and a mixture of nickel metal and Ni−B is obtained in open air. The magnetic properties of the samples made in open air or under nitrogen drastically differ and confirm the XPS studies.

Desulfurization of thioureas, benzimidazoline-2-thiones and 1,3-dihydro-1,3-diaryl-2-thioxopyrimidine-4,6(2H,5H)-diones with nickel boride at ambient temperature

Abstract: Nickel boride is reported to bring about desulfurization and reductive cleavage of N,N′-diarylthioureas to give corresponding anilines and N-methylanilines while N,N′-dialkylthioureas have been observed to undergo desulfurization to give formamidines; benzimidazoline-2-thiones are reported to undergo desulfurization to benzimidazoles and 1,3-dihydro-1,3-diaryl-2-thioxopyrimidine-4,6(2H,5H)-diones have been observed to yield corresponding hexahydropyrimidine-4,6-diones in high yields in dry methanol at ambient temperature.

Facile reduction of benzopyrones with nickel boride: a new method for synthesis of 2H-1-benzopyran-4-ols

Abstract: Benzopyrones and 2H-1-benzopyran-4-ols are important classes of naturally occurring compounds. Benzopyrones e.g., flavones (I), flavanones (II), chromones (III), chromanones (IV), isoflavones (V) and isoflavanones (VI) can be reduced to give different products with different reagents but also undergo ring opening, hydrogenolysis and other side reactions which lower the yields of 2H-1-benzopyran-4-ols.6 The use of sodium borohydride (SBH) with or without the presence of Lewis acids has been attempted for reductions of benzopyrones in different solvents under various conditions. It is reported in the literature that flavones (I) are resistant to SBH reduction as compared to flavanones (II) due to the conjugation of the 2-phenyl group with the enone group. Although LAH, 7 and SBH/Lewis acid 6 have been reported to reduce a few flavones (I), the reaction times are long and the flavan-4ols (VII) are obtained in poor yields. Similarly chromones (III) and isoflavones (V) are reduced with difficulty as compared to their dihydro derivatives, i.e. chromanones (IV) and isoflavanones (VI), due to double bond conjugation. The stereochemistry of the 2H-1-benzopyran-4-ols depends on the nature of the reducing agent. Reductions of flavanones (II) with Pt‐H2, Raney Ni‐EtOH, anhyd. AlCl3, LAH and SBH gave 2,4-cis- (β)-isomers whereas Al‐Hg reduction gave 2,4-trans- (α)-isomers. 5g,16 The isoflavan-4-ols (IX) formed by reduction of isoflavones (V) with SBH are also reported to be 3,4-cis compounds based on J3,4 values. 16,17 Reduction of chromanones (IV) with LAH, SBH and catalytic hydrogenation in the presence of Raney Ni, Pd and Pt 18 yielded cis-2substituted 4-chromanols (VIII). In view of the unpredictable nature of the reduced products from benzopyrones, we have investigated the reductions of (I‐VI) with nickel boride 19 to determine the selectivity and stereochemistry (if applicable) of the products. Benzopyrones (I‐VI) are reported to undergo reduction with nickel boride in dry methanol at ambient temperature to give 2H-1-benzopyran-4-ols in good yields (Table 1). The nickel boride was generated in situ from anhydrous nickel chloride and sodium borohydride. The reactions were sluggish in tetrahydrofuran and dioxan and did not proceed to completion. Flavones (I) and chromones (III) which are resistant to reduction were reduced readily to give the corresponding 2H1-benzopyran-4-ols in methonol. The involvement of nickel boride as a reducing agent was confirmed by carrying out reactions with sodium borohydride alone, since flavone, 2methylchromone and 7-methoxyisoflavone did not undergo

Iron, cobalt and nickel boride as precursor of heterogeneous oxazaborolidine catalysts

Abstract: Heterogeneous 1,3,2-oxazaborolidine catalysts FeB 1.8–0.1 (oxaza) 0.1 , CoB 2−0.1 (oxaza) 0.1 and NiB 2−0.1 (oxaza) 0.1 were prepared by reacting iron, cobalt and nickel boride with (1 S , 2 R )-(+)-2-amino-1,2-diphenylethanol. Over these catalysts, acetophenone can be reduced with high enantioselectivity (ee=97%) by using borane N , N -diethylaniline complex. The capacity to be used again depends on the metal. The detrimental effect of residual water in the metallic salt before reduction, on the enantioselective properties of the catalyst is demonstrated. The formation of the oxazaborolidine ring is substantiated by IR spectroscopy.

Conductive paste, method for manufacturing laminated ceramic electronic component, and laminated ceramic electronic component

Abstract: Provided is a Ag-based conductive paste for a terminal electrode which suppresses oxidation of the Ni surface of an internal conductor and therefore brings about excellent joining with Ni even when baking is performed in the atmosphere in the case where Ni is used as the internal conductor of a laminated ceramic electronic component. The conductive paste includes at least one of an Ag powder and an Ag alloy powder, a nickel boride powder, an inorganic binder and an organic vehicle, wherein the quantity of the nickel boride powder is within the range of about 5% by weight or more, but less than about 60% by weight of the total paste.

Member for high-temperature use superior in corrosion resistance and high-temperature erosion resistance and manufacturing method therefor

Abstract: PROBLEM TO BE SOLVED: To improve a corrosion resistance and a high-temperature erosion resistance of a member used in a high temperature and corrosive environment in which particles fly coming at high speed. SOLUTION: A steel base material is provided with a surface treatment layer comprising a layer mainly consisting of iron boride of 20-50 μm thickness on the base material side and a layer mainly consisting of nickel boride of 10-30 μm thickness thereupon, by means of forming a nickel plated layer on a surface with nickel electroplating and then boronizing the layer in a molten salt bath.

Facile Reduction of Benzopyrones with Nickel Boride: A New Method for Synthesis of 2H-1-Benzopyran-4-ols.

Abstract: Benzopyrones and 2H-1-benzopyran-4-ols are important classes of naturally occurring compounds. Benzopyrones e.g., flavones (I), flavanones (II), chromones (III), chromanones (IV), isoflavones (V) and isoflavanones (VI) can be reduced to give different products with different reagents but also undergo ring opening, hydrogenolysis and other side reactions which lower the yields of 2H-1-benzopyran-4-ols.6 The use of sodium borohydride (SBH) with or without the presence of Lewis acids has been attempted for reductions of benzopyrones in different solvents under various conditions. It is reported in the literature that flavones (I) are resistant to SBH reduction as compared to flavanones (II) due to the conjugation of the 2-phenyl group with the enone group. Although LAH, 7 and SBH/Lewis acid 6 have been reported to reduce a few flavones (I), the reaction times are long and the flavan-4ols (VII) are obtained in poor yields. Similarly chromones (III) and isoflavones (V) are reduced with difficulty as compared to their dihydro derivatives, i.e. chromanones (IV) and isoflavanones (VI), due to double bond conjugation. The stereochemistry of the 2H-1-benzopyran-4-ols depends on the nature of the reducing agent. Reductions of flavanones (II) with Pt‐H2, Raney Ni‐EtOH, anhyd. AlCl3, LAH and SBH gave 2,4-cis- (β)-isomers whereas Al‐Hg reduction gave 2,4-trans- (α)-isomers. 5g,16 The isoflavan-4-ols (IX) formed by reduction of isoflavones (V) with SBH are also reported to be 3,4-cis compounds based on J3,4 values. 16,17 Reduction of chromanones (IV) with LAH, SBH and catalytic hydrogenation in the presence of Raney Ni, Pd and Pt 18 yielded cis-2substituted 4-chromanols (VIII). In view of the unpredictable nature of the reduced products from benzopyrones, we have investigated the reductions of (I‐VI) with nickel boride 19 to determine the selectivity and stereochemistry (if applicable) of the products. Benzopyrones (I‐VI) are reported to undergo reduction with nickel boride in dry methanol at ambient temperature to give 2H-1-benzopyran-4-ols in good yields (Table 1). The nickel boride was generated in situ from anhydrous nickel chloride and sodium borohydride. The reactions were sluggish in tetrahydrofuran and dioxan and did not proceed to completion. Flavones (I) and chromones (III) which are resistant to reduction were reduced readily to give the corresponding 2H1-benzopyran-4-ols in methonol. The involvement of nickel boride as a reducing agent was confirmed by carrying out reactions with sodium borohydride alone, since flavone, 2methylchromone and 7-methoxyisoflavone did not undergo