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Boron compounds are well-known electrophiles. Much less known are their nucleophilic properties. By recognition of the nucleophilicity of the B-H bond, the formation mechanism of octahydrotriborate (B3H8-) was elucidated on the bases of both experimental and computational investigations. Two possible routes from the reaction of BH4- and THF·BH3 to B3H8- were proposed, both involving the B2H6 and BH4- intermediates. The two pathways consist of a set of complicated intermediates, which can convert to each other reversibly at room temperature and can be represented by a reaction circle. Only under reflux can the B2H6 and BH4- intermediates be converted to B2H5- and BH3(H2) via a high energy barrier, from which H2 elimination occurs to yield the B3H8- final product. The formation of B2H6 from THF·BH3 by nucleophilic substitution of the B-H bond was captured and identified, and the reaction of B2H6 with BH4- to produce B3H8- was confirmed experimentally. On the bases of the formation mechanisms of B3H8-, we have developed a facile synthetic method for MB3H8 (M = Li and Na) in high yields by directly reacting the corresponding MBH4 salts with THF·BH3. In the new synthetic method for MB3H8, no electron carriers are needed, allowing convenient preparation of MB3H8 in large scales and paving the way for their wide applications.

The CaBH4 and SrBH4 free radicals were synthesized by the reaction of Ca or Sr vapor with diborane, B2H6. The ?2A1-X?xA1 and B?2E-X?2A1 electroni

Boron-doped carbon nanotubes have been prepared by the pyrolysis of acetylene-diborane mixtures in a stream of helium and hydrogen. The nanotubes so obtained have compositions around C35B. The presence of boron favours nanotube formation and the boron content does not vary with the depth. Considering that the nitrogen-doped nanotubes, reported recently (Chem. Phys. Lett. 287 (1997) 671) have the average composition C35N, it may be possible to use a combination of these p-type and n-type nanotubes for certain applications.

Laser-ablated boron reacts with hydrogen on condensation in excess neon to give BH4 radical, BH4- anion, and B2H6 as the major products. Identifications are based on 10B and D substitution,

Solvate-free sodium octahydrotriborate, NaB3H8, is prepared on a 20 gram scale from sodium amalgam and diborane in diethyl ether. This substance, which is chemically related to borohydride-based compounds being investigated as hydrogen storage materials, is also useful for the preparation of transition-metal complexes bearing B3H8 ligands. Treatment of CrCl3 with NaB3H8 affords a thermally unstable purple liquid thought to be a chromium(III) hydride of stoichiometry CrH(B3H8)2. This hydride converts rapidly at room temperature to the chromium(II) complex Cr-(B3H 8)2, which adopts a square-planar structure in which four hydrogen atoms form the coordination sphere of the chromium atom. This chromium(II) species forms six-coordinate Lewis base adducts Cr(B 3H8)2L2, where L is Et2O, THF, or PMe3; the first two of these adopt trans geometries, whereas the latter is cis. Volatile Cr(B3H8)2 is the first homoleptic transition-metal complex of the octahydrotriborate anion, and it is an excellent single-source precursor for the chemical vapor deposition of thin films of CrB2 at temperatures as low as 200°C. Crystal structures of the new complexes are reported.

The reactions of R4NB3H8 (R = Me, Et, or Bu) with Al(BH4)3 at 20°C afforded R4N[Al(BH4]4] and were accompanied by liberation of tetraborane(10) as the major product. T

The method for synthesis of Bu4NB11H14 by dehydrocondensation of Bu4NB3H8 with diborane in diglyme in the temperature range of 70-90°C was developed. The product is formed in 75-85% yield.

The gas-phase thermolysis of arachno-B6H12 produces predominantly B5H9 and B2H6 in a molar ratio of 2:1 via a first-order reaction having Arrhenius parameters which are essentially identical to those reported for the decomposition of the structurally related B5H11; these results imply a mechanism involving elimination of BH3 as the rate-determining initial step in both reactions.

We have studied the photoelectron spectra of BH3- and BD3- and have measured the electron affinities of borane; we find EA(BH3)=0.038+/-0.015 eV and EA(BD3)=0.027+/-0.014 eV.The peak splittings and intensities demonstrate that the BH3- ion and the BH3 neutral have very similar geometries; our spectra are consistent with a planar structure for both species.Variational calculations of a coupled oscillator basis over an ab initio potential give an excellent fit to the experimental frequencies and photodetachment Franck-Condon factors.This ab initio model leads toequilibrium geometries with both BH3 and BH3- as planar molecules with re(BH3-)=1.207 Angstroem and re(BH3)=1.188 Angstroem.We find ΔHf0 o(BH3-)=23.1+/-3.8 kcal mol-1.

The novel hydride arachno-2-gallatetraborane(10), H2GaB3H8, synthesised by metathesis involving monochlorogallane and tetra-n-butylammonium octahydridotriborate, is characterised by its spectroscopic and chemical properties; electron diffraction confirms

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Platinum dibromide has been found to promote cage growth and dehydrocoupling reactions between diborane and small, polyhedral carboranes and boranes, yieldind either larger single-cage compounds or bridge-substituted diborane-polyhedral carborane/borane complexes.For the catalyzed reaction of diborane with 1,5-C2B3H5, a cage growth reaction accurs to give the new arachno carborane, 5,6-C2B6H12.For 1,6-C2B4H6 and B5H9, cage growth reactions do not take place but instead the coupled diborane-polyhedral cage species 2:1',2'- and 2:1',2'- are obtained.

A method for the synthesis of lithium octahydrotriborate in the form of solvates with dioxane containing one, two, and four dioxane molecules was developed.

The cluster compound Au55(PPh3)12Cl 6 was synthesized via the reduction of (triphenylphosphine)gold chloride with diborane and incorporated into the mesopores of SBA-15 silica. As alternative pathway, the synthe

Potassium germyltrihydroborate, KH3GeBH3, is formed by the reaction of diborane with potassium gennyl. The salt melts with little decomposition at 98-99° and decomposes at 200° to germanium, germanium hydrides, hydrogen, and potassiu

The rates of solvolysis of trimethylamine-monohaloboranes in aqueous dioxane at 25° increase in the series (CH3)3NBH2Cl 3)3NBH2Br 3)3NBH2I. The diiodoborane adduct reacts more slowly than the monoiodo compound but faster than trimethylamine-borane. Only a very slight retardation in rate is observed on substitution of deuterium for hydrogen on boron in the diiodo derivative (kH/kD = 1.1); however, a noticeable solvent isotope effect (kH2O/kD2O = 1.8) is observed for hydrolysis of both the mono- and diiodoborane adducts in 67% aqueous dioxane at 25°. Rates increase with increasing water content of the aqueous dioxane solvent system. No significant effect on rate of acidity is seen for hydrogen ion concentrations as high as 0.3 M or hydroxide ion concentrations up to 0.1 M, nor is the rate appreciably affected by the addition of potassium chloride or potassium iodide up to 0.3 M. The results indicate a mechanism for hydrolysis of the halo compounds quite different from that postulated for amine-BH3 adducts. It is proposed that a rate-determining cleavage of a boron-halogen bond is followed by rapid collapse of an incipient boron(1+) ion. An analogy to nucleophilic substitution reactions in haloborane-amines leading to kinetically stable boronium ions is suggested.

Ammine metal borohydrides display extreme structural and compositional diversity and show potential applications for solid-state hydrogen and ammonia storage and as solid-state electrolytes. Thirty-two new compounds are reported in this work, and trends in the full series of ammine rare-earth-metal borohydrides are discussed. The majority of the rare-earth metals (RE) form trivalent RE(BH4)3·xNH3 (x = 7-1) compounds, which possess an intriguing crystal chemistry changing with the number of ammonia ligands, varying from structures built from complex ions (x = 5-7), to molecular structures (x = 3, 4), one-dimensional chains (x = 2), and structures built from two-dimensional layers (x = 1). Divalent RE(BH4)2·xNH3 (x = 4, 2, 1) compounds are observed for RE2+ = Sm, Eu, Yb, with structures varying from molecular structures (x = 4) to two-dimensional layered (x = 2, 1) and three-dimensional structures (Yb(BH4)2·NH3). The crystal structure and composition of the compounds depend on the volume of the rare-earth ion. In all structures, NH3 coordinates to the metal, while BH4- has a more flexible coordination and is observed as a bridging and terminal ligand and as a counterion. RE(BH4)3·xNH3 (x = 7-5, 4) releases NH3 stepwise during thermal treatment, while mainly H2 is released for x ≤ 3. In contrast, only NH3 is released from RE(BH4)2·xNH3 due to the lower charge density on the RE2+ ion and higher stability of RE(BH4)2. The thermal stability of RE(BH4)3·xNH3 increase with increasing cation charge density for x = 5, 7, while it decreases for x = 4, 6. For x = 3, the thermal stability decreases with increasing charge density, due to the destabilization of the BH4- group, making it more reactive toward NH3. This research provides a large number of novel compounds and new insight into trends in the crystal chemistry of ammine metal borohydrides and reveals a correlation between the local metal coordination and the thermal stability.

The invention relates to a synthesis method of a 9-borabicyclo[3.3.1]nonane dimer. The synthesis method is used for synthesizing the 9-borabicyclo[3.3.1]nonane dimer by performing a hydroboration reaction on a hydroboron, an oxidizing agent and 1,5-cyclooctadiene as the raw materials in a solvent selected from ethers, aromatic hydrocarbons, aliphatic hydrocarbons and the like under the protection of an inert gas. The synthesis method is simple and convenient to operate, mild in conditions, low in cost, high in product yield and product purity, and suitable for certain scale industrial production.

Ammonia borane is a promising hydrogen storage candidate due to its high hydrogen capacity and good stability at room temperature, but there are still some barriers to be overcome before it can be used for practical applications. We present the hydrogen release from ammonia borane confined in templated microporous carbon with extremely narrow pore size distribution. Compared with neat ammonia borane, the hydrogen release temperature of ammonia borane confined in microporous carbon with a pore size of 1.05 nm is significantly reduced, starting at 50 °C and with the peak dehydrogenation temperature centred at 86 °C. The dehydrogenation kinetics of ammonia borane confined in templated microporous carbon is significantly improved and by-products including ammonia and diborane are also completely prohibited without any catalysts involved. The remarkably fast hydrogen release rate and high hydrogen storage capacity from ammonia borane confined in microporous carbon are due to the dramatic decrease in the activation energy of ammonia borane. This has been so far the best performance among porous carbon materials used as the confinement scaffolds for ammonia borane in hydrogen storage, making AB confined in microporous carbon a very promising candidate for hydrogen storage.

The invention discloses an improved methylboronic acid preparation method. The method comprises the following steps: preparing borane and methylboronic acid anhydride at the same time to fully absorb the borane with a small amount of tetrahydrofuran; and treating prepared crude methylboronic acid by using a simple sublimation device in a laboratory to obtain a pure product. The method disclosed by the invention has the characteristics of easiness in operation, high yield, environmental friendliness, suitability for industrial application, and the like.

This paper reports a complete ammonia borane (AB) regeneration process in which Bu3SnH was utilized as a reductant for the reductive dechlorination of BCl3, and Et2PhN was selected as a 'helper ligand' to generate Et2PhN·BH3, which gives rise to a high yield of AB by a base-exchange reaction at ambient temperature.

Solvent-based synthesis and characterization of α-Mn(BH4)2 and a new nanoporous polymorph of manganese borohydride, γ-Mn(BH4)2, via a new solvate precursor, Mn(BH4)2·1/2S(CH3)2, is presented. Manganese chloride is reacted with lithium borohydride in a toluene/dimethylsulfide mixture at room temperature, which yields halide and solvent-free manganese borohydride after extraction with dimethylsulfide (DMS) and subsequent removal of residual solvent. This work constitutes the first example of establishing a successful, reproducible solvent-based synthesis route for a pure, crystalline, stable transition metal borohydride. The new polymorph, γ-Mn(BH4)2, is shown to be the manganese counterpart of the zeolite-like compound, γ-Mg(BH4)2 (cubic, a = 16.209(1) ?, space group Id3a). It is verified that large pores (diameter > 6.0 ?) exist in this structure. The solvate, Mn(BH4)2·1/2S(CH3)2, is subsequently shown to be the analogue of Mg(BH4)2·1/2S(CH3)2. As the structural analogies between Mg(BH4)2 and Mn(BH4)2 became evident a new polymorph of Mg(BH4)2 was identified and termed ζ-Mg(BH4)2. ζ-Mg(BH4)2 is the structural counterpart of α-Mn(BH4)2. All synthesis products are characterized employing synchrotron radiation-powder X-ray diffraction, infrared spectroscopy and thermogravimetric analysis in combination with mass spectroscopy. Thermal analysis reveals the decomposition of Mn(BH4)2 to occur at 160 °C, accompanied by a mass loss of 14.8 wt%. A small quantity of the desorbed gaseous species is identified as diborane (ρm(Mn(BH4)2) = 9.5 wt% H2), while the remaining majority is found to be hydrogen.

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.

A method for synthesizing ammonia borane includes (a) preparing a reaction mixture in one or more solvents, the reaction mixture containing sodium borohydride, at least one ammonium salt, and ammonia; and (b) incubating the reaction mixture at temperatures between about 0° C. to about room temperature in an ambient air environment under conditions sufficient to form ammonia borane. Methods for synthesizing ethylenediamine bisborane, and methods for dehydrogenation of ethylenediamine bisborane are also described.

Dodecaborates, i.e. the [B12H12]2- containing species, are often observed as main intermediates in the hydrogen sorption cycle of metal borohydrides, hindering rehydrogenation. In the decomposition process of Y(BH4/s

The thermally induced de-/rehydrogenation performance of the graphene supported Pt nanoparticles (Pt/G) doped LiBH4 was greatly improved even at very low catalyst content due to a synergetic effect of Pt addition and nanoconfinement in graphene. For the 5 wt% Pt/G doped LiBH4 sample, the onset hydrogen desorption temperature is about 140°C lower than that of the pure LiBH4. With increasing loading of the Pt/G catalysts in LiBH4 samples, the onset dehydrogenation temperature and the two main desorption peaks from LiBH4 were found to decrease while the hydrogen release amount increased. About 17.8 wt% can be released from the 50 wt% Pt/G doped LiBH4 sample below 500°C. Moreover, variation of the equilibrium pressure (350-450°C) indicates that the dehydrogenation enthalpy is reduced from 74 kJ mol-1 H2 for the pure LiBH4 to ca. 48 kJ mol-1 H2 for the 10 wt% Pt/G doped LiBH4, showing improved thermodynamic properties. More importantly, a reversible capacity of ca. 8.1 wt% in the 30th de-/rehydrogenation cycle was achieved under 3 MPa H2 at 400°C for 10 h, indicating that the Pt/G catalysts play a crucial role in the improvement of the hydrogen uptake reversibility of LiBH4 at lower temperature and pressure conditions. Especially, LiBH4 was reformed and a new product, Li2B10H10, was detected after the rehydrogenation process.

The present invention relates to a process for the preparation of compounds containing CF3O groups using compounds containing at least one group Y, in which Y=—Hal, —OSO2(CF2)zF, —OSO2CzH2z+1 (z=1-10), —OSO2F, —OSO2Cl, —OC(O)CF3— or —OSO2Ar, to a process for the preparation of compounds containing CF3O groups using KOCF3 and/or RbOCF3, and to novel compounds containing CF3O groups, and to the use thereof.

The mixtures of LiBH4 with halides of Ce or La in a molar ratio of 3:1 were investigated to explore their hydrogen storage properties. The ball milling of LiBH4 with chloride of Ce or La yielded Ce(BH 4)3 and La(BH4)3, while fluoride of Ce or La did not react with LiBH4 during extended ball milling at room temperature. The dehydrogenation temperatures of the ball-milled mixtures were reduced to 220-320 °C, which were much lower than that of pure LiBH4. The diborane emission during hydrogen release was observed at a low level. The dehydrogenation temperature is found to be affected by the composition of rare earth halides, but less influenced by ball milling time. The endothermic dehydrogenation reactions produced lithium halides, hydrides and borides of the corresponding rare earth element. Moreover, the LiBH4 + 1/3(Ce, La)(Cl, F)3 showed partial reversibility through the formation of an unknown borohydride, allowing for a potential hydrogen storage system.

The dehydrogenation performance of NH3BH3 destabilized by Mg2NiH4 was investigated. It was found that the onset dehydrogenation temperature was reduced, and no gaseous by-products were released during the whole decomposition process. This enhanced dehydrogenation performance could be attributed to the destabilization effect of Mg2NiH4. In comparison with the 2NH3BH 3/MgH2 sample, the dehydrogenation behavior and destabilization mechanism are different. 4NH3BH3/Mg 2NiH4 composite exhibits a three-step decomposition feature. NH3BH3 and Mg2NiH4 decomposed separately. The destabilization effect of Mg2NiH 4 on the chemical bonds of NH3BH3 plays a crucial role in the enhanced dehydrogenation performance. Our results provide a new insight on destabilized dehydrogenation behavior of NH3BH 3 after metal hydrides addition.

Zirconium tetrahydroborate Zr(BH4)4 and its deuteride compound Zr(BD4)4 were successfully synthesized by mechanochemical reaction between NaBH4 or NaBD4 and ZrCl4, reaching yield

Methods of synthesizing ammonia borane are provided. The methods comprise reacting at least one amine borane with ammonia such that ammonia borane is produced. Ammonia borane has a chemical formula Of NH3-BH3 and provides a good source of storage hydrogen making it useful in a variety of applications including a potential hydrogen source for fuel cells. The methods can further comprise separating the ammonia borane from the other products of the reaction. Exemplary methods can produce ammonia borane having purity greater than about 90 percent. In further examples, the methods can produce ammonia borane having purity greater than about 95 percent or greater than about 99 percent.

Heat capacity C p(T) of dysprosium diboride is experimentally investigated at the temperatures of 5-300 K. On the dependence C p(T) smooth anomaly at the temperatures of 15-20 K and sharp anomalies at T m1=47.8 K and T su

Conditions were found for the reaction of NaBH4 with diiodine in diglyme to yield solutions with a predominant content of the B 11H14- anion. Diglyme solutions appropriate for the dehydrocondensation of the B3H8- and B9H14- ions to B11H 14- were again obtained through the selection of solvents and their successive use for purification from admixtures. The solid NaB 11H14 · 3Dn and B4NB11H 14 salts were isolated. Copyright

A method of hydroborating an alkene or alkyne, or reducing an organic functionality, oxidizing primary and secondary alcohols using a fluorous borane-sulfide is disclosed. The method includes regeneration and recycling the fluorous borane-sulfide.

The reactions of the intermetallic compounds CeFe2, CeCo 2, and λ3-ScFe2 with B2H 6 at 4.8 × 103 Pa, 293-573 K, and various contact times were studied. CeFe2 decompose

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 new fluoroboranes exo-2-FB4H9 1 and trans-MeCH≡CHBF2 2 have been obtained unexpectedly and in good yield from the reaction of tetramethylammonium octahydrotriborate (NMe4B3H8) with boro

The interaction of Bu4NB3H8 with B2H6 in diglyme was studied in a temperature range of 40-100°C at Bu4NB3H8 : B2H6 ratios equal to 1 : 1.5 and 1 : 8. The compositions and percentage contents of the reaction products were determined by IR and 11B NMR spectroscopy. Two independent reactions, yielding B9H-14 and B11H-14 ions, were found to occur simultaneously under the chosen conditions For the specified temperatures, exposure times, and feed ratios, the amount of the B9H-14 anion is about 10 mol % and is kept constant. The B9H-14 anion does not react with excess diborane. The maximal Bu4NB11H14 content in the reaction products is 84 mol %.

Improved procedures for the generation of diborane by the reaction of NaBH4 in triglyme or tetraglyme with the BF3 adducts of di-n-butyl ether, tert-butyl methyl ether, monoglyme, dioxane, and tetrahydropyran were developed. In these

Cothermolysis reactions of B6H10 with the binary boranes B2H6, B4H10, B5H9, and B5H11 have been studied by a quantitative mass-spectrometric technique to gain insight into the role of B6H10 in borane interconversion reactions. Except in the B6H10-B5H9 system the initial rate of consumption of B6H10 was found to be considerably more rapid than in the thermolysis of B6H10 alone, indicating that interactions were occuring. Detailed kinetic studies of the B6H10-B2H6 and B6H10-B4H10 reactions showed that the rate of consumption of B6H10 was governed in each case by the rate-determining step in the decomposition of the co-reactant, the orders being 3/2 with respect to B2H6 and 1 with respect to B4H10; a considerable increase in the conversion of B6H10 to B10H14 at the expense of polymeric solids was also observed. Added hydrogen was found to have very little effect on the reaction rates and product distributions in the cothermolysis reactions, in marked contrast to its effect on the reactions of B2H6 and B4H10 alone. The kinetic results are entirely consistent with earlier suggestion, based on qualitative observations, that the reactive intermediates {B3H7} and {B4H8} are scavenged by reactions with B6H10, and suggest strongly that this borane, unlike B6H12, plays a pivotal role in the build-up to B10H14 and other higher boranes.

The salts (Bu4N)[Ln(BH4)4 · nDME] (n = 0, 1) are obtained by an exchange reaction of NaLn(BH4)4 · mDME (Ln = Y, La-Nd, or Sm-Lu; m = 3, 4) compounds with tetrabutylammonium tetrahydroborate. The compounds obtained are studied by IR spectroscopy and thermogravimetry. The properties of the compounds are compared with those of NaLn(BH4)4 · mDME.

Borane adducts with selected N,N-dialkylanilines have been prepared and examined as hydroborating agents. The adduct H3B:NPhPri2 is a solid, considered less desirable than liquid adducts as hydroborating agents. Fortunately, the adducts H3B:NPhBuiMe, H3B: NPhPriMe, H3B:NPhPriEt, and H3B:NPhPriPrn are liquids above 0 °C, hydroborating 1-octene in tetrahydrofuran in less than 1 h at room temperature. Convenient procedures are described for generating gaseous diborane quantitatively, either by thermal dissociation of the borane-N,N-diisopropylaniline adduct or by the reaction of a 2.00 M solution of sodium borohydride in triglyme with a 5.40 M solution of boron trifluoride in triglyme.

The olefin complexes Cp*2M(CH2=CH(R))(H) (R = H (1), CH3 (2); M = Nb (a), Ta (b)) react cleanly with catecholborane (HBCat) and HBO2C6H3-4-(t)Bu (HBCat') to give Cp*2M(H2/s

Protonolysis of the zirconium borohydride [(C5H4R)2Zr(BH4)2] (R = H, Me, SiMe3) with NHMe2PhBPh4 in THF leads to the corresponding cationic zirconium complex [(C5H4R)2Zr-(BH4)(THF)]BPh 4, and the structure of [(C5H4Me)2Zr(BH4)(THF)]BPh 4 was determined. In the presence of phosphine, PMe2Ph, the formation of the cationic hydride [(C5H4R)2ZrH-(PMe2Ph) 2]BPh4 is observed by 1H and 31P NMR followed by a disproportionation and a redox reaction with [BPh4]-, giving the neutral [(C5H4R)2ZrH(μ-H)]2 and the cationic ZrIII species [(C5H4R)2Zr(PMe2Ph) 2]BPh4 characterized by EPR spectroscopy and suggesting a probable pathway in the deactivation of cationic catalyst systems.

Synthesis and structural studies, employing combined NMR, X-ray crystallographic, and ab initio/IGLO/NMR methods, of a variety of new subicosahedral carboranes with adjacent cage carbons are reported. Acetonitrile-induced cage degradation of arachno-4,5-C2B7H12- gave nido-4,5-C2B6H9-(1-) in nearly quantitative yield, which can then be protonated to give the neutral carborane nido-4,5-C2B6H10 (1) in good yield. Both of these nido electroncount clusters are shown to have an arachno-type geometry, i.e. a six-membered open face. The nido-4,5-C2B6H10 (1) hydroborated alkenes or alkynes which following deprotonation gave nido-7-R-4,5-C2B6H8- (2a--c-) ions. Both nido-4,5-C2B6H9- (1-) and nido-4,5-C2B6H10 (1) serve as useful precursors to other adjacent cage-carbon clusters. Thus, nido-4,5-C2B6H9- (1-) reacted with BH3·THF to give arachno-5,6-C2B7H12- (3-) which a single-crystal X-ray diffraction study showed is the first carborane to adopt the n-B9H15 cage geometry. Thermal or chemical degradation of nido-4,5-C2B6H10 (1) gave closo-2,3-C2B5H7 (5) in good to moderate yields. The nido-4,5-C2B6H9- (1-) was also found prone to lose a cage boron as evidenced by its reactions with (η-C5H5)Co(CO)12 and (η6-C6Me6)2Ru2Cl4 which gave closo-3,1,2-(η-C5H5)CoC2B5H7 (6) and closo-3,1,2-(η6-C6Me6)RuC2B5H7 (7), respectively. NMR studies showed the nido-4,5-C2B6H10 (1) was converted to arachno-4,5-C2B6H11- by reaction with LiEt3BH, and an alkyl derivative, arachno-7-CH3-4,5-C2B6H10- (4-), was formed by reacting MeLi with nido-4,5-C2B6H9- (1-) followed by protonation. The closo-2,3-C2B5H7 (5) was also converted in high yields to the smaller nido carborane, nido-2,3-C2B4H8, via reaction with TMEDA/H2O, and to nido-3,4-C2B5H8- (8-) by reaction with LiEt3BH.

Trialkylsilanes or dialkylsilanes react rapidly with boron trichloride in the absence of ethereal solvents or other nucleophiles to form unsolvated dichloroborane. If no substrate is present, dichloroborane disproportionates to trichloroborane and two geo

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Pulsed-laser ablated B atoms react with H2 upon condensation with excess argon to give BH, a (H2)(BH) complex, and B2H6 as the major products. The initial reaction to form BH requires activation energy, and BH reacts with H2 to give additional products. Sharp new bands at 2587.3 and 1129.2 cm-1 exhibit natural isotopic 1:4 doublets for vibrations involving a single boron atom and disappear on annealing to 25 K. Substitution of 10B and D gives shifts that are matched by MBPT(2) calculations of vibrational spectra for planar BH3. Broader bands at 2475.2 and 1134.3 cm-1 exhibit similar isotopic shifts for vibrations of a BH3 submolecule and decrease on annealing to 25 K. The displacements from isolated BH3 frequencies suggest a (H2)(BH3) complex and are in general agreement with recent quantum chemical calculations for BH5. A sharp 2679.9-cm-1 band gives the 10B shift predicted by MBPT(2) calculations for linear HBBH. A weak 2212.8-cm-1 band exhibits the 10B shift and frequency calculated for the strongest band of BH4-. Additional broad absorptions that remain on annealing are attributed to higher boranes.

The reactions of stannane with a variety of organic substrates have been studied. Benzaldehyde, acetone, nitrobenzene, and 2-nitropropane are reduced to benzyl alcohol, isopropyl alcohol, aniline, and isopropylamine, respectively. With boron trifluoride etherate and benzyl chloride, stannane undergoes halogen-hydrogen exchange, while with isopropylamine and acetic acid, it is decomposed catalytically into its elements. Tetrakis(2-cyanoethyl)tin is formed by the addition of stannane to acrylonitrile. Stannane did not react with the following: (a) ethyl acetate, (b) methyl acrylate, (c) aniline, (d) triethylamine, (e) dimethylacetamide, and (f) N-ethylacetamide. The results obtained with stannane are for the most part analogous to those reported for the corresponding organotin hydrides.

Addition of the electrophiles (CH3)+, H+, + to the metalladiborane anions 2-B2H5)>- (M = Fe, Ru, Os) has been investigated.Addition occurs at the metal center.The complexes CH3Os(CO)4(η2-B2H5), HM(CO)4(η2-B2H5) (M = Ru, Os) and (PPh3)AuM(CO)4(η2-B2H5) (M = Fe, Ru, Os) have been formed.NMR spectra of HM(CO)4(η2-B2H5) indicate that the H atom on the metal is cis to the B2H5 ligand.Relative stabilities of the complexes LM(CO)4(η2-B2H5) are in the order M = Os > Ru > Fe for a given electrophile and the order L = (Ph3P)Au > H for a given metal.

The chlorotriborane(7) (B3H6Cl) adduct of N(CH3)3 was formed by the reaction of B4H8·N(CH3)3 with HCl in dichloromethane or with HgCl2 in chloroform. The reaction of B3H7·N(CH3)3 with BCl3 in dichloromethane was found to be a better preparative method for B3H6Cl·N(CH3)3. The BCl3 treatment was employed to convert the N(CH3)2H, N(CH3)H2, NH3, and S(CH3)2 adducts of B3H7 into the corresponding adducts of B3H6Cl. In contrast, B3H7·P(CH3)3 and B3H7·PH3 are inert to BCl3. The B3H6Cl adducts of P(CH3)3 and PH3 could be obtained by treating the B3H7 adducts with a mixture of HCl and BCl3 in dichloromethane. The 11B and 1H NMR spectra of these B3H6Cl adducts showed that their structures were described as 1-(Lewis base)-2-chlorotriborane(7).

The reactions of B2Cl4 with excess B5H9 yield 1-BCl2B5H8 (73%) while those of B2Br4 generate 1-BBr2B5H8 (80%). Ligand exchange of 1-BCl2B5H8 with excess BBr3 forms 1-BBr2B5H8 (86%), that with Hg(CF3)2 results in 1-BF2B5H8 (96%), that with CH3OH generates 1-B(OCH3)2B5H8 (46%), and that with Li(t-Bu) prepares B(t-Bu)(Cl)B5H8 (23%) and B(t-Bu)2B5H8 (20%). The relative thermal stabilities of these products are BF2B5H8 > BCl2B5H8 > BBr2B5H8 > B(OCH3)2B5H8 > B(t-Bu)2B5H8. All of these BX2B5H8 compounds (X = F, Cl, OCH3, t-Bu) decompose to form BX3 and B5H9 as the volatile products. Reactions of BCl2B5H8 with excess B2Cl4 yield (BCl2)3B5H6, a compound of limited thermal stability, but no evidence for further BCl2 substitution on the pentaborane cage was obtained. Reductions of BCl2B5H8 with LiBH4 in C6H5Cl or C6H4Cl2 form apparent equilibrium mixtures of 1:1′,2′-[B5H8][B2H5] and 1:1′-[B5H8][B2H5]. One or both of these compounds decompose with the evolution of B2H6, B5H9, and coupled pentaborane cages (B5H7)n, where n can be at least as large as 8. The 11B NMR and mass spectrometric evidence from the last reaction is consistent with the initial dimerization of the hexaborane 1-BH2B5H8, which is rapidly followed by the formation of 1:1′-[B5H8][B2H5], the cross product arising from the interaction of B2H6 with (BH2B5H8)2, and then isomerization of this heptaborane to 1:1′,2′-[B5H8][B2H5].

The effects of added hydrogen on the kinetics of the first-order thermal decomposition of the two arachno species tetraborane(10) and pentaborane(11) have been studied in detail by a mass-spectrometric method.In the case of B4H10, the order and activation energy were unaltered, but the reaction rate was retarded and there was a marked change in product distribution: the percentage yield of B5H11 remained the same, but B2H6 was formed in preference to B5H9, B6H12, B10H14, and involatile solids.These results provide cogent new evidence that B4H10 decomposes via the single rate-determining step (i), but raise doubts about the validity of subsequent steps in the B4H10+H2 (i) previously proposed mechanism.In the thermolysis of B5H11 there was a dramatic change in product distribution, but the order, activation energy, and initial rate of disappearance of B5H11 were all unaffected by the presence of the added H2.These results establish for the first time that the so-called 'equilibrium' (ii) proceeds in the forward direction via the rate-determining B5H11+H2B4H10+1/2B2H6 (ii) dissociation (iii), followed by the rapid reactions (-i) and (iv).They also imply that in the thermolysis B5H11->+ (iii) 2->B2H6 (iv) of B5H11 in the absence of added H2 the reactive intermediate reacts subsequently with itself and is not consumed by reaction with B5H11.

The kinetics of thermal decomposition of pentaborane(11) have been investigated by a mass-spectrometric technique in the pressure range 1.75-10.50 mmHg and temperature range 40-150 deg C.In conditioned Pyrex vessels the reaction was shown to occur by a homogeneous gas-phase process according to the first-order initial-rate low -d/dt=1.3*107 exp(-72600/RT).The main volatile products are H2 and B2H6, the latter appearing at the rate of ca. 0.5 mol per mol of B5H11 consumed.Pentaborane (9) is also produced, at less than half the rate of B2H6, together with even smaller amounts of hexaboranes and B10H14, and traces of B4H10; some 40-45percent of the boron is converted into involatile solid hydride BHx, where x varies from ca. 2.0 at 40 deg C to ca. 1.1 at 150 deg C.No obvious dependence on temperature was detected in the overall distribution of boron between volatiles and solid, but the production of B5H9 was favoured at higher temperatures.Mechanistic implications of these results are discussed.