Sodium boride

While it is possible to obtain a stoiehiometric Na,BogB,4 sodium boride when operating under Na pressure, the pyrolysis of the compound at low T and in high vacuum leads to Na,B(,gBi4 sodium-deficient phases where x can reach a value of 0 without the collapse of the boron skeleton". 

Sodium boride.—Metallic sodium and boric anhydride react to form a sodium boride.12... 

Little information exists on low-T precipitation of borides from solution. Chromium, cobalt and platinum borides are the only ones claimed to have been obtained from aqueous solution ". Ni2B and C02B are precipitated from a solution of nickel or cobalt acetates by adding a solution of sodium tetrahydroborate ". The formation of these borides at RT gives amorphous products. Hence, heat treatment at 300-700°C leads to crystalline NijB as the main constituent, although the average composition of the precipitate corresponds to NijB . 

Nickel borides are usually prepared by reduction of nickel salts with sodium or potassium borohydride. Two types are used. PI nickel boride is prepared by the reaction between aqueous solutions of nickel salts and a borohy-... 

The boride precipitated from sodium borohydride and cobalt(II) chloride in methanol becomes pyrophoric after vacuum drying. It can safely be stored solvent-moist. 

Chlordane (1 mM) in methyl alcohol (30 mL) underwent dechlorination in the presence nickel boride (generated by the reaction of nickel chloride and sodium borohydride). The catalytic dechlorination of chlordane by this method yielded a pentachloro derivative as the major product having the empirical formula C10H9CI5 (Dennis and Cooper, 1976). 

Sodium hydrogen telluride reacts with epoxides, in accordance with an S 2 displacement, giving rise to telluro-alcohols. These products are useful intermediates since they are easily converted into the corresponding alcohols and ketones by treatment with nickel boride followed by oxidation (reaction (a)) or to alkenes via the corresponding tosylates (reaction b)). ... 

Nickel of activity comparable to Raney nickel is obtained by reduction of nickel salts, e.g. nickel acetate, with 2 mol of sodium borohydride in an aqueous solution and by washing the precipitate with ethanol [13, 47] Procedure 7, p. 205). Such preparations are designated P-1 or P-2 and can be conveniently prepared in situ in a special apparatus [4] Procedure 2, p. 202). They contain a high percentage of nickel boride, are non-magnetic and non-pyrophoric and can be used for hydrogenations at room temperature and... 

Another highly active non-pyrophoric nickel catalyst is prepared by reduction of nickel acetate in tetrahydrofuran by sodium hydride at 45° in the presence of tert-amyl alcohol (which acts as an activator). Such catalysts, referred to as Nic catalysts, compare with P nickel boride and are suitable for hydrogenations at room temperature and atmospheric pressure, and for partial reduction of acetylenes to civ-alkenes [49]. 

Hydrogenation using Raney nickel is carried out under mild conditions and gives cis alkenes from internal alkynes in yields ranging from 50 to 100% [356, 357, 358, 359, 360]. Half hydrogenation of alkynes was also achieved over nickel prepared by reduction of nickel acetate with sodium borohydride (P-2 nickel, nickel boride) [349,361,362] or by reduction with sodium hydride [49], or by reduction of nickel bromide with potassium-graphite [363]. Other catalysts are palladium on charcoal [364], on barium sulfate [365, 366], on... 

Aliphatic and aromatic sulfides undergo desulfurization with Raney nickel [673], with nickel boride [673], with lithium aluminum hydride in the presence of cupric chloride [675], with titanium dichloride [676], and with triethyl phosphite [677]. In saccharides benzylthioethers were not desulfurized but reduced to toluene and mercaptodeoxysugars using sodium in liquid ammonia [678]. This reduction has general application and replaces catalytic hydrogenolysis, which cannot be used [637]. 

Nickel boride, formed in situ from sodium borohydride and nickel chloride, has been used to prepare dihydro derivatives from thiothymine 385 <2001JME1853> and thiobarbituric acid derivatives 388 <2002J(P1)2520>. With 4-thiothymine derivatives, an isomeric mixture of 3,4- and 3,6-dihydro derivatives 386 and 387 was obtained <2001JME1853>, but with 2-thiobarbiturates, clean reduction at the 2-position was able to be achieved <2002J(P1)2520>. 

Hydroborate Reduction. Lithium or sodium tetrahydroborate and diborane can be used for reduction of metal ions, especially light transition metal ions, to produce colloidal metals. For example, colloidal copper protected by polymer was prepared by reduction of copper(II) sulfate by a large excess of sodium tetrahydroborate in the presence of PVP or other polymers (12). A similar procedure for nickel(III) chloride produced nickel boride, not zero-valence nickel metal particles. 

This reaction, which generates nickel boride, is exothermic and evolves hydrogen. Frothing is prevented by keeping the reaction mixture at 0-5°C during addition of the sodium borohydride. 

Tetrasubstituted viodinitro compounds have been converted to olefins by treatment with amalgamated calcium.3214 Various functional groups, such as CN and COOR, did not affect the reaction. Other reagents that have been used include sodium sulfide in DMF,32V nickel boride and ultrasound,330 Bu3SnH,331 and SnCI2.332 Radical-ion mechanisms are likely in all these cases. 

O-p-tolylsulfonyl-a-D-mannoside (39) in 37% yield. Treatment of (39) with sodium iodide in acetone gave the 6-iodo derivative (40), which underwent reduction with hydrogen in the presence of a nickel boride" catalyst" to give methyl 4-0-benzoyl-2,3-0 carbonyl-6-deoxy-o>-D-manno-side (41) in 95% yield. Reaction of (41) with hydrogen bromide in acetic acid effected replacement of the methoxyl group at C-l, affording crystalline... 

Dichloro-2,2-difluoroethylene, 105 (Diethylamino)sulfur trifluoride, 110 Reduction reactions (see also Deoxygenation, Reductive. . . ) of acetals and ketals Dibromoalane, 237 Diisobutylaluminum hydride, 237 Triethylsilane-Tin(IV) chloride, 237 of acetates and other esters to alkanes Nickel boride, 197 Triphenylsilane, 334 of acyl halides to alcohols Sodium cyanoborohydride-Tin(II) chloride, 280... 

Arene(tricarbonyl)chromium complexes, 19 Nickel boride, 197 to trans-alkenes Chromium(II) sulfate, 84 of anhydrides to lactones Tetrachlorotris[bis(l,4-diphenyl-phosphine)butane]diruthenium, 288 of aromatic rings Palladium catalysts, 230 Raney nickel, 265 Sodium borohydride-1,3-Dicyano-benzene, 279 of aryl halides to arenes Palladium on carbon, 230 of benzyl ethers to alcohols Palladium catalysts, 230 of carboxylic acids to aldehydes Vilsmeier reagent, 341 of epoxides to alcohols Samarium(II) iodide, 270 Sodium hydride-Sodium /-amyloxide-Nickel(II) chloride, 281 Sodium hydride-Sodium /-amyloxide-Zinc chloride, 281 of esters to alcohols Sodium borohydride, 278 of imines and related compounds Arene(tricarbonyl)chromium complexes, 19... 

Diphenylphosphine)lithium, 126 Nickel boride, 197 Samarium(II) iodide, 270 to 1,2-disubstituted compounds B-3-Pinanyl-9-borabicyclo-[3.3.1]nonane, 249 Titanium(III) chloride, 302 of phosphorus compounds Lithium aluminum hydride-Cerium(III) chloride, 159 of sulfoxides and sulfones Sodium iodide-Boron trifluoride ether-ate, 282... 

Nickel(II) acetylacetonate, 221 Nickel boride, 197 Nickel carbonyl, 198 Nickel chloride-Lithium, 197 Raney nickel, 197, 265 Raney nickel-2-Propanol, 266 Sodium borohydride-Nickel boride, 280... 

When one component of a bimetallic alloy is leached out, a finely divided metal powder of high surface area results. One of the oldest of these so-called skeletal metal catalysts is Raney nickel10,11. Nickel boride is a more recently developed hydrogenation catalyst prepared by the reduction of nickel salts with sodium borohydride12-14. Bimetallic catalysts are often used to achieve selective saturation of a double bond in bifunctional unsaturated systems, e.g. in dienes. Amorphous metal alloys, a newly developed class of metal catalysts15,16, have also been applied in the hydrogenation of alkenes and dienes. 

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