- Chemical and phase transformations in the systems hydrogen-sorbing intermetallic compound-diborane
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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
- Kravchenko,Kalinnikov,Shilkin
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p. 865 - 867
(2007/10/03)
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- Synthesis and chemical transformations of ionic octahydrotriborates: Cleavage of the B3H8- anion
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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.
- Titov
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p. 1471 - 1479
(2008/10/09)
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- New Synthetic Routes to B4H10 and B5H9
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The boron hydride B4H10 is prepared in high yields (90 percent) through hydride-ion abstraction reactions when a mixture of BH4(-)/B3H8(-) is treated with CH3I or I2, respectively.A high yield (96 percent) method for the conversion of B3H8(-) to B4H10 is the reaction of B3H8(-) with AlCl3 in solvents which do not have any Lewis base character.The solvents are assumed to react as electron acceptors with the intermediate to form B4H10, R(-) and H2 (R-H = solvent).A 1:1 mixture of B4H10 and B5H9 is obtained when B3H8(-) is treated with CH3I or I2.The reaction can be viewed to involve an initial step in which unstable B3H7 is generated which immediately undergoes decomposition to give B4H10, B5H9 and H2.Treatment of B4H10 with (n-Bu)4NBr results in the formation of B3H-Br(-) which decomposes slowly at 0 deg C to form B5H9.An alternative synthesis of B5H9 via hydride-ion abstraction is possible through the reaction of (n-Bu)2O-BF3 with B3H8(-) in ether solvents. - Keywords: Syntheses of B4H10 and B5H9
- Brellochs, Bernd,Binder, Herbert
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p. 648 - 653
(2007/10/02)
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- New, systematic syntheses of boron hydrides via hydride ion abstraction reactions: Preparation of B2H6, B4H10, B5H11, and B10H14
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The boron hydrides B2H6, B4H10, B5H11, and B10H14 are prepared in good yields through hydride ion abstraction reactions when the borane anions BH4-, B3H8-, B4H9-, and B9H14- respectively are treated with 1 molar equiv of a Lewis acid BX3 (X = F, Cl, or Br), generally in the absence of a solvent, for reaction periods of 1-4 h. A high-yield (85-90%) method for the conversion of B5H9 to B9H14- is presented as the precursor to the practical conversion of B5H9 to B10H14 (45-50%). Additionally, treatment of the anion BrB3H7- with BBr3 results in the formation of 2-BrB4H9 in low yield (15%). The hydride ion abstraction reactions by BBr3 and BCl3 lead to the new anions HBBr3- and HBCl3-.
- Toft, Mark A.,Leach,Himpsl, Francis L.,Shore, Sheldon G.
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p. 1952 - 1957
(2008/10/08)
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