19624-22-7

Usage

Uses

1. Used in Rocket Propulsion:
Pentaborane is used as a rocket fuel due to its high energy content and flammability. In the 1950s, it was explored as a potential rocket fuel, but its extreme flammability and toxicity have limited its commercial use.
2. Used as a Reducing Agent in Propellant Fuels:
Pentaborane is used as a reducing agent in propellant fuels, taking advantage of its high reactivity and energy content. However, its use in this application is also limited by its hazardous properties.
3. Used in Air-Breathing Engines:
Pentaborane is used as fuel for air-breathing engines, which are engines that intake atmospheric air for combustion. Its high energy density and flammability make it a suitable candidate for this application, despite the associated risks.

Air & Water Reactions

Highly flammable. May ignite spontaneously in air [Merck 11th ed. 1989]. Slowly decomposes in water.

Reactivity Profile

Pentaborane is an extremely reactive reducing agent. Can ignite spontaneously in contact with air and many other materials. Reactions with oxygen are often violently explosive. Reacts with ammonia to form a diammoniate. Is stabilized by the formation of complexes with N, O, P, or S. Is stable in hydrocarbon solvents, but forms shock sensitive solutions in most carbonyl containing solvents.

Health Hazard

May cause death or permanent injury after very short exposure to small quantities.

Fire Hazard

Ignites spontaneously in air. Reacts violently with halogenated extinguishing agents. Boron hydrides present considerable fire and explosion hazard. They undergo explosive reaction with most oxidizing agents, including halogenated hydrocarbons. Fires tend to reignite. On decomposition, Pentaborane emits toxic fumes and can react vigorously with oxidizing materials. Avoid dimethyl sulfoxide, water, most oxidizing agents (including halogenated hydrocarbons). Avoid direct sunlight and sources of ignition, decomposes very slowly at 302. Hazardous polymerization may not occur.

Safety Profile

Poison by inhalation and intraperitoneal routes. Dangerous fire hazard by chemical reaction; spontaneously flammable in air. Dangerous explosion hazard. To fight fire, use special fire-fighting materials; water is not effective; reacts violently with halogenated extinguishing agents. Get instructions from supplier. Explosive reaction with oxygen. Forms shock-sensitive solutions in solvents containing carbonyl, ether, or ester functions; or halogens. Incompatible with dimethyl sulfoxide. Upon decomposition it emits toxic fumes of B. See also BORANES and BORON COMPOUNDS

Potential Exposure

Pentaborane is used in rocket propellants and in gasoline additives.

Shipping

UN1380 Pentaborane, Hazard Class: 4.2; Labels: 4.2-Spontaneously combustible material, 6.1-Poisonous materials. Inhalation Hazard Zone A.

Incompatibilities

Pentaborane is an extremely reactive reducing agent. It can ignite spontaneously in contact with air and many other materials. Reactions with oxygen are often violently explosive. Reacts with ammonia to form a diammoniate. Reacts on contact with water, oxidizers, halogens, including halogenated hydrocarbons. May sel-heat and ignite spontaneously in moist air, decomposes @ 150C. Hydrolyzes slowly with heat in water to form boric acid. Contact with solvents, such as ketones, ethers and esters form shock-sensitive compounds. Pentaborane is stable in hydrocarbon solvents, but forms shock sensitive solutions in most carbonyl containing solvents. Corrosive to natural rubber, some synthetic rubbers and to some lubricants. Avoid dimethyl sulfoxide, direct sunlight and sources of ignition.

InChI:InChI=1/B5H9/c6-2-1-3(2,6)5(1,8-3)4(1,2,7-2)9-5/h1-5H

Upstream product

• 1333-74-0 hydrogen 
• 18283-93-7 tetraborane 
• 10294-33-4 boron tribromide 
• 311-28-4 tetra-(n-butyl)ammonium iodide 
• 7637-07-2 boron trifluoride 
• 110-18-9 N,N,N,N,-tetramethylethylenediamine 
• 23777-80-2 hexaborane⁽¹⁰⁾ 
• 18972-20-8 2,3-dicarba-nido-hexaborane⁽⁸⁾ 
• 7440-21-3 monosilane 
• 7803-51-2 phosphan 
• 82544-57-8 1-(dichloroboryl)pentaborane 
• 120385-35-5 1-(dibromoboryl)pentaborane 
• 75-69-4 trichlorofluoromethane 
• 23753-67-5 1-bromopentaborane⁽⁹⁾ 

Downstream Products

• 17702-41-9 nido-decaborane 
• 23777-80-2 hexaborane⁽¹⁰⁾ 
• 18433-84-6 pentaborane⁽¹¹⁾ 
• 19287-45-7 diborane 
• 23753-67-5 1-bromopentaborane⁽⁹⁾ 
• 10294-33-4 boron tribromide 
• 67495-88-9 (C₆H₅)3PCH₃⁽¹⁺⁾*B₅H₈^(1-)={(C₆H₅)3PCH₃}{B₅H₈} 
• 12080-12-5 C₆H₅C₂B₄H₇ 
• 1838-15-9 (diphenylamino)borane 
• 389070-33-1 arachno-B₉H₁₃(PPh₃)2 

Related news

Mechanism and chemical inhibition of the Pentaborane (cas 19624-22-7) oxidation reaction☆09/07/2019

The objective of this work has been to learn how to inhibit chemically the pentaboraneoxygen reaction with a view to developing improved fire protection systems. Rates of pyrolysis of pentaborane and ignition induction times of pentaboraneoxygenargon mixtures were measured in a shock tube ...detailed

Relevant academic research and scientific papers

Chemical and phase transformations in the systems hydrogen-sorbing intermetallic compound-diborane

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

Synthesis and chemical transformations of ionic octahydrotriborates: Cleavage of the B3H8- anion

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.

Formation of metallaboranes from the group IV transition metals and pentaborane(9): Crystal and molecular structure of [(Cp2Zr)2B5H8] [B11H14]

The reactions between [(C5H5)2MCl2] (where M = Ti, Zr, Hf) and Li[B5H8] in a variety of solvents have been investigated. In the case of Zr, a pale orange solid, μ-(Cp2ClZr)B5H8 (1), is formed in 70% yield. Compound 1 exists as a B5H9 cage with a Cp2ClZr moiety replacing a bridging H atom. The variable temperature NMR spectra of 1 reveal two fluxional processes, one (ΔG? = 54 kJ mol-1) which renders a plane of symmetry in the molecule and a higher temperature one (ΔG? = 48 kJ mol-1) which renders all the basal B atoms equivalent. Dynamic processes are suggested to account for these observations. Passage of a CH2Cl2 solution of 1 through silica gel affords 2, [(Cp2Zr)2B5H8] [B11H14], a yellow, air-stable, crystalline solid, in 14% yield. The cation in 2, [(Cp2Zr)2B5H8]+, consists of a distorted spiro[2.2]pentane-like B5 moiety comprising two B3 triangles sharing a naked boron vertex. The two triangles are twisted 73° with respect to each other, and the two [Cp2Zr] groups bond in a trihapto arrangement to the two opposite B-B-B edges. Each exterior B-Zr edge is H-bridged, and the B atoms possess terminal hydrogens. Reactions of Cp2HfCl2 with Li[B5H8 lead to the formation of the analogue of 2, [(Cp2Hf)2B5H8] [B11H14] (3). The precursor to 3, that is, the Hf analogue of 1, is not observed. Reaction between Li[B5H8] and Cp2TiCl2 afforded no identifiable products, but reaction with CpTiCl3 resulted in cage coupling and the formation of B1OH14.

Kinetic studies of reactions of hexaborane(10) with other binary boranes in the gas phase

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.

Synthesis and Reactivity of New Aminopentaboranes

of 2-XB5H8 (X = Br or Cl) with secondary or tertiary silylamines proceed with elimination of hydrogen halides and/or halosilanes and attachment of amino groups to the clusters. Reaction of 2-BrB5H8 with (Me3-Si)2NH produces 2-[(Me3Si)2N]B5H8 in 57% yield. Other bis(silyl)amines react analogously. With (t-Bu)(Me3-Si)NH, 2-BrB5H8 produces 2-[(Me3Si)(t-Bu)N]B5H8 and hypho-2,3-μ-(t-BuNH)B5H10. (t-Bu)(Et3Si)NH reacts analogously. Low temperature analysis of the (t-Bu)(Me3Si)NH reaction in dichloromethane solution via 11B NMR spectroscopy discloses a dual reaction pathway producing a 2-aminopentaborane and a proposed arachno-2,3-μ-(t-BuNH)B5H8 intermediate which subsequently reacts with boranes to form hypho-2,3-μ-(t-BuNH)B5H8. When the above reaction is carried out in B5D9 solution, normal nido-[(t-Bu)(Me3Si)N]B5H8 and partially deuterated hypho-2,3-μ-(t-BuNH)B5H10 is formed. Reaction of 2-[(Me3Si)2N]B5H8 with BCl3 produces 2-[(Me3Si)2N·BCl3]B5H 8, and with (t-Bu)CN produces 2,3-μ-(t-BuCH=N)-2-[(Me3Si)2N]B5H 7.

Small heteroborane cluster systems. 3. Characterization, deprotonation, and transition-metal chemistry of the small phosphorus-bridged pentaborane(9) system (μ-diphenylphosphino)pentaborane

The complete spectroscopic characterization of the small phosphorus-bridged pentaborane(9) cluster (μ-diphenylphosphino)pentaborane, [μ-(C6H5)2PB5H8] (1), is reported. The MNDO calculated structure for 1 shows that the B P-B interaction can be best described as consisting of two two-center-two-electron B-P bonding interactions. Indirect support for the involvement of the lone pair of electrons on the phosphorus in cage bonding is obtained from the failure of 1 to react with [(CH3CN)3Mo(CO)3] under forcing conditions. Compound 1 is readily and quantitatively bridge-deprotonated by the action of NaH to produce the corresponding anion, Na[(μ-(C6H5)2P)B5H7] (2). Compound 2 reacts with 1 equiv of [Fe(η5-C5H5)(CO)2I] to yield the iron complex [(μ-(C6H5)2P)B5H 7Fe(η5-C5H5)(CO)2] (3) in high yield as an air-stable, yellow solid. A single-crystal X-ray analysis of 3 shows that the structure consists of a highly distorted square pyramid of boron atoms in which the B(2) H -B(3) bond in B5H9 has been subrogated by a B-P-B bridge and that the [Fe(η5-C5H5)(CO)2] unit is σ-substituted for a terminal proton on B(4). The phosphorus atom exhibits a distorted tetrahedral geometry and is located 0.516 A? below the least-squares basal-B4 plane. The B(2) B(3) atomic distance of the B- P B bridge was found to be 2.68 A?. The structure is formally derived from a two-electron reduction of a nido-pentaborane structure by the three-electron-donating phosphino unit to produce an arachno-pentaborane structure that is directly analogous to arachno-B5H11. Crystallographic data: space group P1/n (No. 14), a = 10.989 (2) A?, b = 13.460 (4) A?, c = 14.454 (5) A?, α = γ = 90 00°, β = 95.42 (2), V = 2128 (1) A?3, Z = 4 molecules/cell.

Formation of amine, phosphine, and thioether adducts of chlorotriborane(7)

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).

Fluorination of boron chlorides and boron bromides by reaction with bis(trifluoromethyl)mercury, trichlorofluoromethane, or tribromofluoromethane: Synthesis of BF2B5H8

The interaction of BCl3 with excess CFCl3 has been examined by 11B and 19F NMR. Although small amounts of BFCl2 and BF2Cl, 9% each, are observed after 283 h at 65°C, BF3 is not a major product. At 130°C, however, BF3 is formed in 89% yield after 33 h. Boron trifluoride is isolated in 98 and 97% yields from the reactions of BCl3 and BBr3, respectively, with CFBr3 at 130 °C. At ambient temperature, Hg(CF3)2 reacts with BCl3 and BBr3, generating BF3 in 99 and 98% yields, respectively. The reaction of B2Cl4 with excess CFCl3 was followed spectroscopically at 65, 90, and 130°C, and the 19F chemical shifts of the partially fluorinated diboron tetrahalides have been assigned. Diboron tetrafluoride was isolated from the reaction between B2Cl4 and CFBr3 in 89% yield, from B2Br4 and CFBr3 in 78% yield, and from B2Cl4 and Hg(CF3)2 in 89% yield. Within 45 min the reaction between 1-BCl2B5H8 and Hg(CF3)2 produces the new compound 1-BF2B5H8 in 96% yield. Tetraboron tetrachloride is by far the least reactive of the boron chlorides examined.

Influence of Added Hydrogen on the Kinetics and Mechanism of Thermal Decomposition of Tetraborane(10) and of Pentaborane(11) in the Gas Phase

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.