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Sodium tetrahydroborate (NaBH4) and dodecahydro-closo-dodecaborate (Na2B12H12) are both important inorganic compounds presenting multiple applications. Nevertheless, multistep and complicated conditions are usually demanded for their synthesis. In order to simplify the synthesis processes, we design a novel and facile solvent-free method for synthesizing NaBH4 or Na2B12H12 from NaNH2 and B10H14. The product of either NaBH4 or Na2B12H12 is manipulable by simply adjusting the ratio of NaNH2 to B10H14. The reaction equations of synthesizing NaBH4 and Na2B12H12 are proposed and verified, and the reaction pathways are elucidated. The findings here supply new insight to synthesize metal dodecaborates using the strategy of equal electron body for the first time and may shed light on synthesis of small metal B-H compounds from large B-H clusters.

Sodium borohydride, NaBH4, was successfully synthesized via solid-state reaction under Ar instead of H2 atmosphere. A 4NaH-NaBO2-2SiO2 ternary mixture was first ball-milled and pressed into pellet, and then calc

It has been reported that sodium (potassium) borohydride can be formed by reaction of sodium (potassium) borate with Mg and hydrogen or magnesium hydride. However, few investigations on reaction mechanism have been reported. Here, we studied the NaBH4 formation mechanism of Mg + NaBO2 + 2H2 = NaBH4 + MgO through morphology observations, structure and micro composition analyses. It was found that when heating the reactor to 400 °C, NaBO2 particles were agglomerated with Mg particles and a NaBO2 network was formed due to the sintering effect. With further heating the reactor, a porous product layer (composed of NaBH4 and MgO) was formed on Mg particles. It was found that no matter whether Mg was hydrogenated or not, Mg could react with sodium borate and hydrogen to form sodium borohydride. Elevating the reaction temperature was of benefit to NaBH4 formation. Higher NaBH4 yield can be obtained by using partially hydrogenated then dehydrogenated Mg.

The tetraphosphenediides M2[t-Bu3SiPPPPSi-t-Bu 3] (M = Li, Na, K) were accessible by the reaction of P4 with the silanides M[Si-t-Bu3] (M = Li, Na, K), whereas M 2[t-Bu3SiPPPPSi-

An advanced process for the production of sodium borohydride (NaBH 4) as a hydrogen storage material was developed, which applied the dynamic hydriding and dehydriding behaviors of protide (H-) in Mg-H system under transitional temperature conditions. An abundant natural resource named borax (Na2B4O7?10H2O) and the anhydrous sodium metaborate (NaBO2) recovered from the spent fuel as NaBO2?4H2O were used as the starting material in the present process. Powder-state Mg played an important role in the transitional hydriding and dehydriding process where the gaseous hydrogen was converted to protide at the extreme surface of Mg to form NaBH 4 in exchange with the simultaneous transition of oxygen in NaBO 2 to form MgO. In the present process, the protide as the most reactive state among the four states of hydrogen is applied for the synthesis of NaBH4, which can exist in metal-hydrogen complexes, such as NaAlH4 and NaBH4. The NaBH4 yield was reached higher than 90% by a single batch process but was found to be largely dependent on the rate of temperature change and the particle size, i.e., the specific surface area of Mg particles.

A simple and efficient way to synthesize unsolvated sodium octahydrotriborate has been developed. This method avoids the use of dangerous starting materials and significantly simplifies the reaction setup, thus enabling convenient large-scale synthesis. The structure of the unsolvated compound has been determined through powder X-ray diffraction.

A significant obstacle in the large-scale applications of sodium borohydride (NaBH4) for hydrogen storage is its high cost. Herein, we report a new method to synthesize NaBH4 by ball milling hydrated sodium tetraborate (Na2B4O7 ? 10H2O) with low-cost Al or Al88Si12, instead of Na, Mg or Ca. An effective strategy is developed to facilitate mass transfer during the reaction by introducing NaH to enable the formation of NaAlO2 instead of dense Al2O3 on Al surface, and by using Si as a milling additive to prevent agglomeration and also break up passivation layers. Another advantage of this process is that hydrogen in Na2B4O7 ? 10H2O serves as a hydrogen source for NaBH4 generation. Considering the low cost of the starting materials and simplicity in operation, our studies demonstrate the potential of producing NaBH4 in a more economical way than the commercial process.

NaBH4·2H2O and NaBH4 were studied by single-crystal Xray diffraction and vibrational spectroscopy. In NaBH 4·2H2O, the BH4- anion has a nearly ideal tetrahedral geometry and is bridged with two Na+ ions through the tetrahedral edges. The structure does not contain classical hydrogen bonds, but reveals strong dihydrogen bonds of 1.77-1.95 A. Crystal structures and vibrational spectra of NaBr·2H2O and NaBH 4·2H2O reveal many similarities. The unit cell volume of NaBH4·2H2O increases linearly with temperature between 200 and 313 K. At 313-315 K, the hydrate decomposes into NaBH4 and H2O, which react to release hydrogen. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

A preliminary study was conducted on the coal desulfurization process via NaBO2 electroreduction with pulse voltage using a boron-doped diamond (BDD) thin film electrode. It has been proved that NaBO2 was converted into NaBH4 by 11B NMR. The factors that influence the conversion rate of NaBO2 into NaBH4 and coal desulfurization efficiency were investigated. Under the conditions of -1.5 V forward pulse voltage, +0.5 V reverse pulse voltage, 0.2 mol L-1 NaBO2 concentration, 0.5 mol L-1 NaOH concentration, 2 s forward pulse duration, 1 s reverse pulse duration, 50 g L-1 coal concentration, 0.8 mmol L-1 NiCl2 concentration and 2.5 h electrolytic time, a higher desulfurization efficiency (64%) was obtained compared with the common electrochemical desulfurization (ECDS) process using a Pt electrode. By analyzing and comparing the coal samples and electrolytes before and after desulfurization it was indicated that the removed S from the coal sample in the form of gaseous H2S was mainly converted into Na2S and Na2Sx and boron (B) recycling was realized during coal desulfurization. Particularly, the combustion characteristics of coal were improved after desulfurization. Finally, the desulfurization mechanism was proposed. All these results indicated that the desulfurization process via NaBO2 electroreduction with pulse voltage using a BDD thin film electrode is effective and highly promising for coal desulfurization.

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Zirconium and hafnium tetrachlorides react with NaBH4 in dimethoxyethane (DME) to give .These compounds react with Bu4NBH4 and Ph4PBH4 to give (R4E).Bidentate and tridentate BH4(1-) occur in (1-) according to IR spectr

Mechanochemical treatment (ball-milling) of NaAlH4-Ca(BH4)2 mixtures leads to partial formation of NaBH4 and Ca(AlH4)2 by a metathesis reaction. The reaction proceeds to different extents depending on the applied ball-milling times, which is confirmed by powder X-ray diffraction and infrared spectroscopy. Additionally, an in-situ synchrotron radiation powder X-ray diffraction study reveals that the metathesis reaction continues due to thermal treatment while the data also supports a two-step decomposition of the formed Ca(AlH4)2. Finally, the reactive hydride composite system was investigated by mass spectrometry and Sieverts' measurement, which reveal release of ～6 wt% H2 at T 400 °C.

A convenient method was developed to synthesize NaBH4 by the reaction of MgH2 with Na2B4O7 through ball milling at room temperature. In order to improve the sodium borohydride yield, Na compounds were added to compensate the Na insufficiency in reactants when MgH2 instead of NaH was used as the reducing agent. It was found that Na2CO3 addition was better than NaOH or Na2O2 addition in increasing the borohydride yield.

Reactions of Ln(BH4)3(THF)3 (Ln = Nd, Ce) and M2dddt (M = Na, K; dddt = 5,6-dihydro-1,4-dithiine-2,3- dithiolate) in THF or pyridine gave, after addition of 18c6 (18-crown-6), several crystalline compounds which all contain the tris(dithiolene) Ln(dddt)3 unit. Crystals of [Na(18c6)(py)2] 2[Na(18c6)(py)][Nd(dddt)3(py)]·3py (1·3py) are built up from discrete mononuclear cationic and anionic species whereas crystals of {[Na(18c6)(py)2]0.5[Na(18c6)(py) 1.5][Na1.5Nd(dddt)3]}∞ (2) are composed of discrete [Na(18c6)(py)x]+ cations and polymeric anionic two-dimensional layers in which the Nd(dddt)3 units are linked to three neighbors by sodium atoms to form a honeycomb network. Analysis of the temperature dependence of the molar magnetic susceptibility of 2 shows that χMT decreases from 1.63 cm3 K mol -1 at 300 K down to 0.6 cm3 K mol-1 at 5 K, due to the crystal-field splitting of the 4I9/2 free-ion state. Complexes {[Na3(18c6)1.5Nd(dddt) 3(THF)]·3THF}∞ (3·3THF) and {[K 3(18c6)1.5Nd(dddt)3(py)]·3py} ∞ (4·3py) exhibit neutral polymeric layers with the Nd(dddt)3 units linked by M2(18c6) fragments. In the cerium compound {[Na2(18c6)Na(py)2Ce(dddt) 3(py)]·3py}∞ (5·3py), each Ce(dddt)3 unit is linked to two neighbors only by Na 2(18c6) moieties, giving infinite zigzag chains.

The feasibility of preparing sodium borohydride by electrolyzing sodium metaborate has been demonstrated from the thermodynamic perspective and the cyclic voltammetry curves of different electrode materials were investigated. Furthermore, under the condition of copper as a working electrode, the changing relations between the cell current and working electrode potential were compared with different conditions, such as membrane, the concentrations of alkali and sodium metaborate. The copper electrode whose electrode potential is 1.17 V was chosen as a working electrode. In a home-made electrolytic cell which contains of cation-exchange membrane, sodium borohydride was prepared by electrolyzing sodium metaborate and the product was titrated using national standard method.

Commencing from metal hydrides, versatile synthesis, purification, and desolvation approaches are presented for a wide range of metal borohydrides and their solvates. An optimized and generalized synthesis method is provided for 11 different metal borohydrides, M(BH4)n, (M = Li, Na, Mg, Ca, Sr, Ba, Y, Nd, Sm, Gd, Yb), providing controlled access to more than 15 different polymorphs and in excess of 20 metal borohydride solvate complexes. Commercially unavailable metal hydrides (MHn, M = Sr, Ba, Y, Nd, Sm, Gd, Yb) are synthesized utilizing high pressure hydrogenation. For synthesis of metal borohydrides, all hydrides are mechanochemically activated prior to reaction with dimethylsulfide borane. A purification process is devised, alongside a complementary desolvation process for solvate complexes, yielding high purity products. An array of polymorphically pure metal borohydrides are synthesized in this manner, supporting the general applicability of this method. Additionally, new metal borohydrides, α-, α′- β-, γ-Yb(BH4)2, α-Nd(BH4)3 and new solvates Sr(BH4)2·1THF, Sm(BH4)2·1THF, Yb(BH4)2·xTHF, x = 1 or 2, Nd(BH4)3·1Me2S, Nd(BH4)3·1.5THF, Sm(BH4)3·1.5THF and Yb(BH4)3·xMe2S ( x = unspecified), are presented here. Synthesis conditions are optimized individually for each metal, providing insight into reactivity and mechanistic concerns. The reaction follows a nucleophilic addition/hydride-transfer mechanism. Therefore, the reaction is most efficient for ionic and polar-covalent metal hydrides. The presented synthetic approaches are widely applicable, as demonstrated by permitting facile access to a large number of materials and by performing a scale-up synthesis of LiBH4.

In this work, we explored the possibility of NaBH4 synthesis when Mg reacted with hydrous sodium borates under hydrogen. It was found that Mg could react with the water in molten hydrous borates to form MgO and release hydrogen, which can be us

We have studied the reaction of MnCl2 with MBH4 (M = Li+, Na+, K+) in Et2O. Crystal structures of two new intermediates, named [{M(Et2O)2}Mn2(BH4)5] (M = Li+, Na+), were elucidated by X-ray diffraction. Mn(BH4)2 in a mixture with LiBH4 or NaBH4 forms upon the solvent removal in a vacuum. [{M(Et2O)2}Mn2(BH4)5] contains 2D layers formed by Mn and BH4 groups, linked through the alkali metal atoms coordinated to Et2O. The loss of the solvent molecules leads to the segregation of the partially amorphous or nanocrystalline LiBH4/NaBH4 and a creation of the 3D framework of the crystalline Mn(BH4)2. While using LiBH4 led to Mn(BH4)2 contaminated with LiCl, presumably due to an efficient trapping of the latter salt by the [Mn(BH4)2-Et2O] system, the reaction with NaBH4 produced chlorine-free Mn(BH4)2 accompanied with NaBH4. Using KBH4 led to the formation of K2Mn(BH4)4 as a second phase. Two pyridine-containing solvomorphs, [Mn(py)3(BH4)2] and [Mn(py)4(BH4)2]·2py, were isolated in pure form. However, Mn(BH4)2 partly decomposes upon removal of pyridine molecules. This journal is

A series of organic derivatives of magnesium borohydride, including Mg(BH4)2·1.5DME (DME = 1,2-dimethoxyethane) and Mg(BH4)2·3THF (THF = tetrahydrofuran) solvates and three mixed-cation borohydrides, [Cat]2[Mg(BH4)4], [Cat] = [Me4N], [nBu4N], [Ph4P], have been characterized. The phosphonium derivative has been tested as a precursor for synthesis of inorganic mixed-metal borohydrides of magnesium, Mx[Mg(BH4)2+x], M = Li-Cs, via a metathetic method. The synthetic procedure has yielded two new derivatives of heavier alkali metals M3Mg(BH4)5 (M = Rb, Cs) mixed with amorphous Mg(BH4)2. Thermal decomposition has been studied for both the organic and inorganic magnesium borohydride derivatives. Amorphous MgB2 has been detected among the products of the thermal decomposition of the solvates studied, together with organic and inorganic impurities.

Hydroboration reactions of carboxylic acids using sodium aminodiboranate (NaNH2[BH3]2, NaADBH) to form primary alcohols were systematically investigated, and the reduction mechanism was elucidated experimentally and computationally. The transfer of hydride ions from B atoms to C atoms, the key step in the mechanism, was theoretically illustrated and supported by experimental results. The intermediates of NH2B2H5, PhCH= CHCOOBH2NH2BH3-, PhCH= CHCH2OBO, and the byproducts of BH4-, NH2BH2, and NH2BH3- were identified and characterized by 11B and 1H NMR. The reducing capacity of NaADBH was found between that of NaBH4 and LiAlH4. We have thus found that NaADBH is a promising reducing agent for hydroboration because of its stability and easy handling. These reactions exhibit excellent yields and good selectivity, therefore providing alternative synthetic approaches for the conversion of carboxylic acids to primary alcohols with a wide range of functional group tolerance.

Sodium borohydride (NaBH4) is among the most studied hydrogen storage materials because it is able to deliver high-purity H2 at room temperature with controllable kinetics via hydrolysis; however, its regeneration from the hydrolytic product has been challenging. Now, a facile method is reported to regenerate NaBH4 with high yield and low costs. The hydrolytic product NaBO2 in aqueous solution reacts with CO2, forming Na2B4O7?10 H2O and Na2CO3, both of which are ball-milled with Mg under ambient conditions to form NaBH4 in high yield (close to 80 %). Compared with previous studies, this approach avoids expensive reducing agents such as MgH2, bypasses the energy-intensive dehydration procedure to remove water from Na2B4O7?10 H2O, and does not require high-pressure H2 gas, therefore leading to much reduced costs. This method is expected to effectively close the loop of NaBH4 regeneration and hydrolysis, enabling a wide deployment of NaBH4 for hydrogen storage.

The regeneration of sodium borohydride (NaBH4) is crucial to form a closed cycle after it either supplies hydrogen energy via a hydrolysis process or provides energy through electron transfer at the anode of direct borohydride fuel cells (DBFCs). In both of these cases, the spent fuels are NaB(OH)4 from NaBO2 aqueous solution. However, the current regeneration process from (NaB(OH)4)·xH2O to form NaBH4 by reduction reaction and calcination at high temperature with metal hydrides as reducing agents is very expensive. In this work, we developed a simple regeneration process via ball milling with Mg-Al alloys as the reducing agent for NaB(OH)4 under an argon atmosphere. Under optimized conditions, a high yield of about 72% of NaBH4 could be obtained. Mechanistic study showed that all the hydrogen atoms from NaB(OH)4 remain in NaBH4 and no additional hydrogen sources are needed for the reduction process. The inexpensive Mg-Al alloy works as a reducing agent transforming the H+ to H- in NaBH4. This approach demonstrates a ～20-fold cost reduction compared with the method using metal hydrides. This opens the door to the commercial implementation of simple ball milling processes for the regeneration of spent NaBH4 from NaB(OH)4 with cheap reducing agents.

The reactivity of sodium amidoborane (NaNH2BH3) as a Br?nsted and Lewis base was studied systematically. The [NH2BH3]– anion can act as a proton acceptor or a hydride donor in different types of reactions. In reactions with very weak Br?nsted acids such as cyclopentadiene, ammonia, and pyrazole, the [NH2BH3]– anion acts as a proton acceptor through the lone pair on N. The reactions of [NH2BH3]– with stronger Br?nsted acids are complicated. In the reaction with ammonium chloride or acetic acid, [NH2BH3]– accepts a proton, reforming NH3BH3. However, in the reaction with HCl or methanol, N–B bond cleavage occurs. [NH2BH3]– can also donate hydride in some reactions. The possible mechanisms of these reactions are discussed.

The application of NaBH4 hydrolysis to hydrogen generation is currently obstructed by its regeneration. Finding a simple and low cost method to regenerate its hydrolysis byproduct is therefore important. Herein, the regeneration of NaBH4 is obtained by reacting its direct hydrolysis byproduct, NaBO2·2H2O, with a mixture of Mg and Mg2Si by ball milling. In this reaction, the reduced agents are only metal and intermetallic compounds, thus hydrogen in the regenerated NaBH4 (Hδ?) derives solely from NaBO2·2H2O (Hδ+). The introduction of Mg2Si increases the NaBH4 regeneration yield to 86%, which is the highest regeneration yield reported for NaBH4 until now. The reaction mechanism was also clarified for the first time.

The KBH4?NaBF4 mixture was studied by thermal analysis (differential scanning calorimetry). Chemical analysis, X-ray powder diffraction analysis, IR spectroscopy, and 11B and 19F MAS NMR spectroscopy showed that the primary stage of the complex pyrolysis process is a metathesis reaction between components to form a new mixture, NaBH4?KBF4, the decomposition of which with the release of gaseous products and the formation of polyhedral borohydride compounds (mainly B12H12 2-) in the solid residue begins at a temperature of about 563 K. At a certain ratio between reactants in the initial mixture KBH4?NaBF4, the B12H12 2- anion can form with the material participation of the BF4 - anion.

Abstract In this work we demonstrate enhanced hydrogen storage capacities through increased solubility of sodium borate product species in aqueous media achieved by adjusting the sodium (NaOH) to boron (B(OH)3) ratio, i.e., M/B, to obtain a distribution of polyborate anions. For a 1:1 mol ratio of NaOH to B(OH)3, M/B = 1, the ratio of the hydrolysis product formed from NaBH4 hydrolysis, the sole borate species formed and observed by 11B NMR is sodium metaborate, NaB(OH)4. When the ratio is 1:3 NaOH to B(OH)3, M/B = 0.33, a mixture of borate anions is formed and observed as a broad peak in the 11B NMR spectrum. The complex polyborate mixture yields a metastable solution that is difficult to crystallize. Given the enhanced solubility of the polyborate mixture formed when M/B = 0.33 it should follow that the hydrolysis of sodium octahydrotriborate, NaB3H8, can provide a greater storage capacity of hydrogen for fuel cell applications compared to sodium borohydride while maintaining a single phase. Accordingly, the hydrolysis of a 23 wt.% NaB3H8 solution in water yields a solution having the same complex polyborate mixture as formed by mixing a 1:3 M ratio of NaOH and B(OH)3 and releases >8 eq of H2. By optimizing the M/B ratio a complex mixture of soluble products, including B3O3(OH)52-, B4O5(OH)42-, B3O3(OH)4-, B5O6(OH)4- and B(OH)3, can be maintained as a single liquid phase throughout the hydrogen release process. Consequently, hydrolysis of NaB3H8 can provide a 40% increase in H2 storage density compared to the hydrolysis of NaBH4 given the decreased solubility of sodium metaborate.

We report a novel family of hydrogen-rich materials-alkali metal di(amidoborane)borohydrides, M(BH3NH2BH2NH2BH3). The title compounds are related to metal amidoboranes (amidotrihydroborates) but have higher gravimetric H content. Li salt contains 15.1 wt% H and discharges very pure H2 gas. Differences in thermal stability between amidoboranes and respective oligoamidoboranes explain the release of the ammonia impurity (along with H2) during the thermal decomposition of light alkali amidoboranes, LiNH2BH3, NaNH2BH3 and NaLi(NH2BH3)2, and confirm the mechanism of the side decomposition reaction. This journal is

MgB12H12 has been widely discussed as an intermediate in the hydrogen sorption cycles of Mg(BH4)2, but its properties such as stability and reactivity are still unknown. We achieved the synthesis of MgB12H12via the reaction between Mg(BH 4)2 and B2H6 at 100 to 150 °C. When bulk Mg(BH4)2 was used as the starting material, a yield of 10.2 to 22.3 mol% was obtained, which was improved to 92.5 mol% by using Mg(BH4)2 nanoparticles. The as-synthesized MgB 12H12 decomposed into boron between 400 and 600 °C, preceded by a possible polymerization process. The formation mechanism of MgB12H12 and its role in the decomposition process of Mg(BH4)2 are discussed. the Partner Organisations 2014.

In the present work, the decomposition behaviour of NaZn(BH 4)3 nanoconfined in mesoporous SBA-15 has been investigated in detail and compared to bulk NaZn(BH4)3 that was ball milled with SBA-15, but not nanoconfined. The successful incorporation of nanoconfined NaZn(BH4)3 into mesopores of SBA-15 was confirmed by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, 11B nuclear magnetic resonance, nitrogen absorption/desorption isotherms, and Fourier transform infrared spectroscopy measurements. It is demonstrated that the dehydrogenation of the space-confined NaZn(BH4)3 is free of emission of boric by-products, and significantly improved hydrogen release kinetics is also achieved, with pure hydrogen release at temperatures ranging from 50 to 150 °C. By the Arrhenius method, the activation energy for the modified NaZn(BH4)3 was calculated to be only 38.9 kJ mol-1, a reduction of 5.3 kJ mol-1 compared to that of bulk NaZn(BH4)3. This work indicates that nanoconfinement within a mesoporous scaffold is a promising approach towards stabilizing unstable metal borohydrides to achieve hydrogen release with high purity.

Tuning the hydrogen storage properties of complex metal hydrides is of vast interest. Here, we investigate the hydrogen release and uptake pathways for a reactive hydride composite, LiBH4-NaAlH4 utilizing in situ synchrotron radiation powder X-ray diffraction experiments. Sodium alanate transforms to sodium borohydride via a metathesis reaction during ball milling or by heating at T～95 °C. NaBH4 decomposes at ～340 °C in dynamic vacuum, apparently directly to solid amorphous boron and hydrogen and sodium gas and the latter two elements are lost from the sample. Under other conditions, T=400 °C and p(H2)=～1 bar, NaBH4 only partly decomposes to B and NaH. On the other hand, formation of LiAl is facilitated by dynamic vacuum conditions, which gives access to the full hydrogen contents in the LiBH4-NaAlH4 system. Formation of AlB2 is observed (T～450 °C) and other phases, possibly AlBx or Al1-xLixB2, were observed for the more Li-rich samples. This may open new routes to the stabilization of boron in the solid state in the dehydrogenated state, which is a challenging and important issue for hydrogen storage systems based on borohydrides.

Reactions of MBH4 (M = Li, Na, K) with tBuOH, Ph3COH, PhOH, F5C6OH, and 2,4-tBu2C6H 3OH in THF in a 1:1 ratio were followed by 11B NMR spectroscopy. No M[H2B(OR)2] species could be detected, but minor amounts of M[H3BOR] and larger amounts of M[HB(OR) 3]. In the reaction of LiBH4 with 2,4-tBu 2C6H3OH also a fair proportion of (RO) 2BH was generated. The perfluorophenolato borane (F5C 6O)2BH·THF was prepared from the phenol and BH 3·THF in THF solution. It is unstable to disproportionation. Compound (C6F5O)3B·THF was isolated and its crystal structure determined. Reaction of LiBH4 with F 5C6OH in hexane generated a solid that proved to be Li[H2B(OC6F5)2]. It is unstable in THF. On the other hand, 2,2′-dihydroxydiphenyl in the presence of secondary amines reacts to give Li[C12H8O 2B(NR2)2] (3-5). Li[B(O2C 12H8)2], 2, is formed when HN(tBu)Ph is used as a secondary amine. The unstable phthalatoborane H{C6H 4[C(O)O]2}BH·THF (7), is stabilized as its pyridine adduct (phth)BH·py (8). 7 reacts with 3 equivalents of LitBu to give [Li(HBtBu)3] (11), isolated as its tris(THF) solvate. Analogously, 7 reacts with LiNMePh to produce compound Li[HB(NMePh)3] (10). Similarly, 7 and NaOtBu (molar ratio 1:3) give access to Na[HB(OtBu) 3] (9). In attempts to grow single crystals, specimens resulting from a hexane solution showed that partial hydrolysis has occurred to give Na[HB(OtBu)3]·Na[(tBuO)2BO]·Na[tBuOB(O)H], which crystallizes as a centrosymmetric dimer. While catecholborane when treated with LitBu in THF and DME gave access to (dme)2Li[catB(tBu) 2], 12 (dme)2, several compounds were observed when Li piperidide was used as nucleophile. Amongst these, the most interesting one was (dme)(THF)Li2(cat)(catBH), 13 (dme)THF, the crystal structure of which was determined. In all cases where the borate species carried OR groups the O atoms of the RO or PhO group coordinate with the alkali metal cation. DFT calculations for the series of anions H4-nBXn- showed that HBX3- is the most stable species for X = F, OH, NH2. This confirms experimental results.

The reactions of zirconium, yttrium, and zinc tetrahydroborate complexes NaMn(BH4)n + 1(DME)m (M = Zr, Y, Zn; DME = 1,2-diethoxyethane) with triethylcarbinol in tetrahydrofuran were studied. The products of the transformation of the BH4 groups in these reactions were isolated and identified. The reaction of triethylcarbinol with the yttrium and zirconium complexes yields bis(3-ethyl-3-pentoxy)borane BH[OC(C2H5)3]2, whereas the reaction with the zinc complex yields tris(3-ethyl-3-pentyl) borate B[OC(C 2H5)3]3. The physicochemical properties of the compounds obtained were studied. The crystal and molecular structure of B[OC(C2H5)3]3 was determined. Crystals of B[OC(C2H5)3] 3 are trigonal: a = 12.562(2) ?, c = 9.048(2) ?, Z = 2, space group P 3. The B atom is located at the crystallographic axis 3, the BO3 fragment is planar (B-O = 1.362(2) ?). The C 2H5 groups experience considerable thermal vibrations.

Powdery mixture containing borate and alkali eat metal, for example, magnesium is prepared. Hydrogen atmosphere is fed to the mixture, for example, from hydrogen gas source. The mixture is reacted in hydrogen atmosphere under pressure below reaction equilibrium pressure where hydride of magnesium can exist in stable.

The present invention relates to an improvement in the recovery of boron values from a mixture of alkali metal borate and alkali metal hydroxide representing discharged fuel from a hydrogen generator apparatus. The mixture is reacted with carbon dioxide and a lower alcohol to form trialkyl borate, alkali bicarbonate and water. A porous water-absorbing material is added to the reaction mixture to absorb water as it forms thereby improving the yield of trialkyl borate. The trialkyl borate is converted to alkali borohydride that is used in the fuel.

Based on three chemical states of hydrogen: protide (H-), protium (H0) and proton (H+), a triangular hydrogen energy system was proposed. The transfers among protide, protium and proton attracted our attention. We experimentally proved that NaBH4 as a protide carrier can release its energy through a fuel cell (borohydride fuel cell) directly or generate hydrogen gas for polymer electrolyte membrane fuel cell application. The used fuel (meta-borate) can be reverted to NaBH4 through a reaction with a saline hydride (MgH2).

New octahydrotriborates LiB3H8·4Dn (Dn is dioxane), LiB3H8·2Dn, NaB3H 8·Dn, KB3H8·2.5Dn, [Mg(NH 3)6](B3H8)2, [Mg(Dg) 2](B3H8)2 (Dg is diglyme), [Mg(Dg)2](BH4)(B3H8), [Ca(Dg) 2](BH4)(B3H8), [Sr(Dg) 2](B3H8)2, and [C(NH 2)3]B3H8 were synthesized, and solvated salts with the B3H8- anion were prepared. It was shown that LiB3H8 forms hydrazinates of variable composition containing one to four hydrazine moles and the ammoniates LiB3H8·4NH3 and LiB3H 8·3NH3. The properties of the resulting salts and their solvates were studied. The temperature limits of the partial or complete desolvation of the solvates were established. The solubility of NaB 3H8·3Dn and tetraalkylammonium octahydrotriborates in organic solvents was studied over a wide temperature range. The heats of combustion in an oxygen atmosphere were measured, and the enthalpies of formation were calculated: ΔfH0(Me 4NB3H8) = -157.4 kJ/mol, Δy fH0(Et4NB3H8) = -262.5 kJ/mol, and ΔfH0(Bu4NB3H 8) = -443.8 kJ/mol. The destruction of the B3H 8- anion to give the BH4- ion and unstable borane B2H4 was found and confirmed experimentally for the first time. The destruction was studied in reactions of octahydrotriborates with Lewis bases (hydrazine and triphenylphosphine) and Lewis acids (AlCl3 and Al(BH4)3) and also in heat treatment. The B2H4 borane was isolated as the B 2H4·2PPh3 adduct. The reaction NaB 3H8·Dn → NaBH4 + B 5H9 + (H2 + Dn) can be conveniently used to prepare pentaborane(9) under laboratory conditions. The reaction of octahydrotriborate with aluminum chloride Bu4NB3H 8 + AlCl3 → Bu4N[Cl3Al(BH 4)] + B4H10 allows one to prepare tetraborane(10) with a fairly high yield and with a satisfactory degree of purity.

The exchange reaction of NaM(BH4)4 · nDME (M = Y, Tm, Lu; n = 3, 4; DME = 1,2-dimethoxyethane) with tetraphenylphosphonium tetrahydridoborate yields the salts (Ph4P)[M(BH4)4]. The compounds were studied by IR spectroscopy; the crystal structure of (Ph4P)[Tm(BH4)4] (1) was determined by X-ray crystallography. Compound 1 is tetragonal, a = 14.344(2) A?, c = 13.517(3) A?, V = 2781.1(8) A?3, Z = 4, space group I41/a. Crystals of 1 are composed of (Ph4P)+ cations and [Tm(BH4)4]- anions held together by Coulomb interaction. Tm and P atoms occupy special fourfold positions in different axes 4 in space group I41/a. The Tm atom is bound to a tetrahedral array of four B atoms of BH-4 anions (Tm-B, 2.46(1) A?) presented to the central atom by three hydrogen atoms (η3 coordination mode; Tm-Hav, 2.32(8) A?). The fourth H atom of a boron hydride tetrahedron is located roughly in the extension of the Tm-B line (the TmBH(1b) angle is 176(8)°). In the (Ph4P)+ cations, the P-C bonds, 1.791(6) A?, and angles at the P atom, 108°-110(5)°, have standard values.

The reaction of sodium metal with dimethylamine-borane in THF yields Na((H3B)2NMe2) (1) which can be isolated as {Na[(H3B)2NMe2]}5*THF or as Na[(H3B)2NMe2]*15-crown-5 (2) and Na[(H3B)2NMe2]*benzo-15-crown-5 (3) after addition of the appropriate crown ether to the THF solution of 1. Reaction of 1 with ZrCl4 yields Me2HN-BH2-NMe2-BH3 (4), the structure of which has been determined. In THF solution, 1 reduces aldehydes, ketones, acyl chlorides, and esters to the corresponding alcohols. It also reacts slowly with nitriles and allylbenzene. Compound (1)5*THF crystallizes in an extended three-dimensional lattice, in which the Na atoms are coordinated by 6-9 hydridic H atoms, while 3 is a molecular compound in the solid state. Only one hydrogen atom of each BH3 group coordinates to the sodium center. On the other hand, 4 forms dimeric associates in the solid state through N-H...H-B interactions.

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The arachno-[B9H13]2- dianion has been synthesized as the K2[B9H13] and Na2[B9H13] salts through deprotonation of K[B9H14] by KH in glyme and through deprotonation of Na[B9H14] by NaNH2 in liquid ammonia. Due to explosions that occurred during the preparation and handling of both Na2[B9H13] and Na[B9H14], studies of Na2[B9H13] were terminated. The potassium salt is insoluble in ether solvents but is soluble in liquid ammonia. It is solubilized in acetonitrile when a cryptand is added as a complexing agent. The structure of [(Krypt2.2.2)K]2[B9H13] was determined from a single-crystal X-ray study. The basic structure of [B9H13]2- is similar to that of the room-temperature structure of [B9H14]- with one of the hydrogens removed. Endo hydrogens on the perimeter of the open face of the structure are disordered. This disorder implies the existence of isomers in the solid state and is compatible with the fluxional character of these hydrogens in solution.

The simple preparation of monoalkyl- and dialkylboranes previously developed by the addition of methyl iodide to lithium monoalkyl- and dialkylborohydrides in tetrahydrofuran solution has been expanded to alternative procedures involving other solvents, such as diethyl ether (EE) and n-pentane, and other reagents, such as phenol, acetic acid, methanesulfonic acid, ethereal hydrogen chloride, trimethylsilyl chloride, and trimethylsilyl methanesulfonate. The practicality of generating monoalkyl- and dialkylboranes from the corresponding borohydrides has been demonstrated in representative solvents utilizing appropriate reagents. The reaction of lithium borohydride with the above reagents was also studied. The reaction of lithium borohydride with 1 equiv of acetic acid produces a mixture of lithium tetraacetoxyborohydride and unreacted lithium borohydride instead of the expected lithium monoacetoxyborohydride. Because of discrepancies with the reported results for sodium borohydride, the study was extended to this reagent.

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