Sodium fluoroborate

Boric acid (6.2 g.) is added, with coolii, to 25 g. of 40% hydrofluoric acid contained in a Pt dish. The mixture is left standing for six hours at room temperature, then cooled with ice, and 5.3 g of dry N%CO is added. The solution is then evaporated vintil crystallization starts. The salt can be recrystallized from water, wherelq lai e, beautiful single crystals can be obtained. The NaBF is finally dried under vacuum. 

Formula weight 109.815. Colorless salt crystallizes in the anhydrous form as clear, orthc onal, stubby prisms. Anhydrous NaBF does not etch glass. Readily soluble in water. Rhombic crystals, isodimorphous with NaClQ 

Balz and E. Wilke-Dorfurt. Z. anorg. allg. Chem. 159,197 (1927). 

Boric acid (6.2 g.) is added to 25 g. of 40% hydrofluoric acid solution contained in an ice-cooled platinum dish. The solution is allowed to stand at room temperature for six hours. At the end of this period it is again chilled with ice, and 5N KOH solution is added with constant stirring until the color of methyl orange changes. Crystalline KBF precipitates out at the same time. The mother liquor and subsequent water washings are decanted and the crystals dried under vacuum. The yield is 90%. 

Technical grade KHFg (100 g.) is dissolved in 250 ml. of water contained in a polyethylene beaker. The KgSiFg and the undissolved KHFg are filtered off after several hours of standing the clear solution is placed in an ice-cold water bath and 40 g. of boric acid is added with stirring. Rapid dissolution occurs. Small crystals separate from the solution within an hour. They are suction-filtered on a fritted glass filter, washed with a small amount of ice-cold water and with 95% methanol solution and acetone. The salt is then dried at 120°C. 

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Toxicity. Fluoroborates are excreted mostly in the urine (22). Sodium fluoroborate is absorbed almost completely into the human bloodstream and over a 14-d experiment all of the NaBF ingested was found in the urine. Although the fluoride ion is covalently bound to boron, the rate of absorption of the physiologically inert BF from the gastrointestinal tract of rats exceeds that of the physiologically active simple fluorides (23). 

Sodium Fluoroborate. Sodium fluoroborate is prepared by the reaction of NaOH or Na2C02 with fluoroboric acid (51), or by treatment of disodium hexafluorosihcate with boric acid. 

Sodium fluoroborate [13755-29-8] M 109.8, m 384 , d 2.47, pK -4.9 (for fluoroboric acid H30 BF4 ). Crystd from hot water (50mL/g) by cooling to 0 . Alternatively, purified from insoluble material by dissolving in a minimum amount of water, then fluoride ion was removed by adding cone lanthanum nitrate in excess. After removing lanthanum fluoride by centrifugation, the supernatant was passed... 

Sodium ferrate, in sodium nitrite production, 22 855 Sodium ferrite, 14 543 Sodium fluoride, 22 825, 8 340 Sodium fluoroborate manufacture, 4 155 physical properties of, 4 152t thermodynamic properties of, 4 154t uses of, 4 156... 

B. Preparation of Cyclopropyldiphenylsulfonium Fluoroborate. A suspension of 118.7 g. (0.339 mole) of 3-chloropropyldiphenylsulfonium fluoroborate (Note 2) in 500 ml. of dry tetrahydrofuran (Note 12) is placed in a 2-1., one-necked flask equipped with a magnetic stirring bar and nitrogen inlet tube under nitrogen. Then 5-g. portions of 55% sodium hydride-mineral oil dispersion (15.2 g., 0.350 mole) are added in 30-minute intervals. The resulting mixture is stirred (Note 13) at room temperature for 24 hours. An aqueous solution of 25 ml. of 48% fluoroboric acid (Note 14), 15 g. of sodium fluoroborate (Notes 7, 15), and 400 ml. of water is added to the well-stirred reaction to destroy residual hydride and swamp out chloride ion (Note 16). After 5 minutes 300 ml. of methylene chloride is added, and the top methylene chloride layer is removed from the lower aqueous layer (Note 17). The methylene chloride solution is then extracted with 100 ml. of water. This water layer is combined with the first aqueous layer, and the combined water layers are extracted with an additional 100 ml. of methylene chloride. The methylene chloride portions are combined, dried over anhydrous sodium sulfate, and evaporated at reduced pressure until precipitation occurs. Addition of 1 1. of ether completes the precipitation of the salt. 

The checkers prepared sodium fluoroborate by neutralization of an ice-cold, aqueous, 42% solution of fluoroboric acid with an equivalent amount of sodium carbonate and addition of dry ethanol to the reaction mixture to effect complete crystallization of the product. The crystals were purified by washing with ethanol, and the purified material was obtained in 80% yield. 

A boron analog - sodium borohydride - was prepared by reaction of sodium hydride with trimethyl borate [84 or with sodium fluoroborate and hydrogen [55], and gives, on treatment with boron trifluoride or aluminum chloride, borane (diborane) [86. Borane is a strong Lewis acid and forms complexes with many Lewis bases. Some of them, such as complexes with dimethyl sulfide, trimethyl amine and others, are sufficiently stable to have been made commercially available. Some others should be handled with precautions. A spontaneous explosion of a molar solution of borane in tetrahydrofuran stored at less than 15° out of direct sunlight has been reported [87]. 

Sodium fluoroborate [13755-29-8] M 109.8. Crystd from hot water (50ml/g) by cooling to 0°. Alternatively, purified from insoluble material by dissolving in a minimum amount of water, then fluoride ion... 

Five grams of copper sulfate 5-hydrate are dissolved in 20ml of water and 3.5g of dipropylenetriamine are added with stirring. Acetone is added to the blue liquid until the product has been completely precipitated as an oil the supernatant liquid should be almost colorless. The oil is repeatedly triturated with small portions of acetone in a mortar until it forms a solid it is brought onto the filter with the same solvent and washed with a little ether. While the deep blue product is still moist, it is rapidly transferred to a vacuum desiccator and pumped dry. The material is extremely deliquescent. Losses in the preparation are only mechanical. The complex sulfate gives no precipitate with solutions of iodide, dithionate, ferricyanide, or persulfate ions. In concentrated aqueous medium, however, the addition of solid sodium fluoroborate causes partial precipitation of the relatively insoluble complex fluoroborate. 

Two and six-tenths grams of nickel sulfate 6-hydrate are stirred with 10ml of water while 2.6g of den is added. Then 3g of sodium fluoroborate is mixed with the liquid and the violet precipitate is filtered and drained well. The product is soluble in acetone. 

In general the required diazonium fluoroborate is obtained as a precipitate when a concentrated solution of sodium fluoroborate is added to a solution of a diazonium salt. In an alternative procedure (e.g. the preparation of p-fluoroanisole, cognate preparation in Expt 6.77), the amine is diazotised in solution in aqueous fluoroboric acid. The diazonium fluoroborates are less sensitive to shock and heat than most diazonium salts and may be prepared and handled in the dry state with relative safety. Most diazonium fluoroborates have definite decomposition temperatures and the rates of decomposition, with few exceptions, are easily controlled. Diazonium fluoroborates containing the nitro group, however, usually decompose suddenly and with violence on heating in such cases the fluoroborate should be mixed with 3-4 times its weight of dry sand and heated cautiously until decomposition commences. 

Dissolve 46.5 g (45.5 ml, 0.5 ml) of aniline in a mixture of 126 ml of concentrated hydrochloric acid and 126 ml of water contained in a 1-litre beaker. Cool to 0-5 °C in a bath of ice and salt, and add a solution of 36.5 g (0.53 mol) of sodium nitrite in 75 ml of water in small portions stir vigorously with a thermometer and maintain the temperature below 10 °C, but preferably at about 5 °C by the addition of a little crushed ice if necessary. The diazotisation is complete when a drop of the solution diluted with 3-4 drops of water gives an immediate blue coloration with potassium iodide-starch paper the test should be performed 3-4 minutes after the last addition of the nitrite solution. Prepare a solution of 76 g (0.69 mol) of sodium fluoroborate (1) in 150 ml of water, cool and add the chilled solution slowly to the diazonium salt solution the latter must be kept well stirred and the temperature controlled so that it is below 10 °C. Allow to stand for 10 minutes with frequent stirring. Filter the precipitated benzenediazonium fluoroborate with suction on a Buchner funnel, drain well and wash the yellow solid with about 30 ml of ice-water, 15 ml of methanol and 30-40 ml of ether suck the solid as free as possible from liquid after each washing (2). Spread the salt upon absorbent filter paper and allow to dry overnight, if possible in a current of air. The yield of benzenediazonium fluoroborate is 60—65 g the pure salt melts with decomposition at 119-120 °C. 

Notes. (1) The use of sodium fluoroborate solution supersedes the less convenient fluoroboric acid and permits the preparation to be carried out in ordinary glass vessels. If it is desired to employ fluoroboric acid HBF4, it can be prepared by adding 100 g of AR boric acid in small proportions to 325 g of AR hydrofluoric acid (40% HF) cooled in ice the hydrofluoric acid is contained in a polypropylene beaker, in a beaker coated with wax or in a lead vessel. One-third of the above solution should be employed in the preparation. Handle with great care. 

Cognate preparations, p-Fluorotoluene. Diazotise 53.5 g (0.5 mol) of p-toluidine in a mixture of 126 ml of concentrated hydrochloric acid and 126 ml of water contained in a 1-litre beaker following the procedure given in Expt 6.71. Add a chilled solution of 76 g (0.69 mol) of sodium fluoroborate in 150 ml of water slowly and with good stirring to the cold diazonium salt... 

Dissolve 34 g (0.25 mol) of o-nitroaniline in a warm mixture of 63 ml of concentrated hydrochloric acid and 63 ml of water contained in a 600-ml beaker. Place the beaker in an ice-salt bath, and cool to 0-5 °C while stirring mechanically the o-nitroaniline hydrochloride will separate in a finely divided crystalline form. Add a cold solution of 18 g (0.26 mol) of sodium nitrite in 40 ml of water slowly and with stirring to an end-point with potassium iodide-starch paper do not allow the temperature to rise above 5-7°C. Introduce, while stirring vigorously, a solution of 40 g (0.36 mol) of sodium fluoroborate in 80 ml of water. Stir for a further 10 minutes, and filter the solid diazonium fluoroborate with suction on a Buchner funnel. Wash it immediately once with 25 ml of cold 5 per cent sodium fluoroborate solution, then twice with 15 ml portions of rectified (or industrial) spirit and several times with ether in each washing stir the fluoroborate well before applying suction. The o-nitrobenzenediazonium fluoroborate weighs about 50 g (86%) the pure substance melts with decomposition at 135 °C. 

Burgstahler et al. diazotized the sparingly soluble hydrochloride of 3,4-di-r-butylaniline at O-S", treated the filtered solution with sodium fluoroborate, and obtained the diazonium fluond>orate. This salt underwent slow solvolysis in a mixture of acetic acid — acetic anhydride with formation of the corresponding acetate. 

To a dichloromethane solution (5 ml) containing triphenylbismuth difluoride (239 mg, 0.50 mmol) and 4-methylphenylboronic acid (68 mg, 0.50 mmol) was added boron trifluoride diethyl etherate (65 p.1, 0.50 mmol) at 0°C, and the resulting mixture was stirred at room temperature for 2 h. An aqueous solution (20 M) of sodium fluoroborate (500 mg, 4.55 mmol) was then added and the two-phase mixture was vigorously stirred for 30 min. The water phase was extracted with dichloromethane (5 ml X 2), and the combined extracts were dried over MgS04, and passed through a short silica gel column. Evaporation of the solvent under reduced pressure left an oily residue, which was crystallized from ether-dichloromethane (10 1) to yield (4-methylphenyl)triphenylbismuthonium tetrafluoroborate (300 mg, 97%) as a colorless solid [980M4332]. 

Apreton R Borate(l-), tetrafluoro-, sodium Boron sodium fluoride (BNaF4) EINECS 237-340-6 NSC 77386 Pyricit Sodium borofluoride Sodium boron fluoride Sodium boron tetrafluoride Sodium fiuoborate Sodium fluoborate (Na(BF4 Sodium fluoroborate (NaBF4) Sodium tetrafluoroborate Sodium tetrafluoroborate 1-). Used as a fluorinating agent. Rectangular prisms mp = 384° = 2.4700 soluble in H2O (108 g/100 ml), less... 

A solution of sodium fluoroborate (about 5.38 moles) is obtained by adding NaF (900 g) to a mixture of boric acid (333 g) and concentrated HC1 (1338 ml) with stirring and cooling, followed after 2 h by filtration.1256... 

Figure 6.6 Effect of composition on the 10" Pa s isokom temperature for sodium borate and sodium fluoroborate melts...

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