- Studies on BCl and on the exchange reaction of BCl3 with polyboron flourides
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Gaseous BCl has been prepared at low pressure by reaction of BCl3 with boron at 2000 °C or by decomposition of B2Cl4 using either an electric discharge or using flash thermolysis at 1150 °C, and then condensed at - 196 °C. Reasons are discussed why each method gives BCl capable of generating (Cl2B)3BCO when the condensate at - 196 °C is treated with CO, but B4Cl4 is only formed from BCl prepared from B2Cl4. The stepwise conversion of (F2B)3BCO to (Cl2B)3BCO by treatment with BCl3 has been followed by 11B NMR spectroscopy. Evidence from mass spectrometry and 11B NMR spectroscopy suggests that reaction of polyboron fluorides, particularly B8F12 and B10F12, with BCl3 yields a new form of B9Cl9 of, as yet, unknown structure which converts slowly to closo-B9Cl9 or closo-B8Cl8 depending on the solvent.
- Pardoe, Jennifer A.J.,Norman, Nicholas C.,Timms, Peter L.
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p. 543 - 548
(2008/10/08)
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- Ein neuer Zugang zu halogenierten Carboranen
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The copyrolysis of tetrahalogenodiborane(4) (B2X4, X = Cl, Br) or the halogenated carbon compounds such as CX4 or C2X4 yields the new carboranes C2B5X7 and C2B7Cl9 in addition to the vinyl compound C2Br3BBr2 as some of the products.
- Haubold, Wolfgang,Keller, Willi
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p. C54 - C56
(2007/10/02)
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- Fluorination of boron chlorides and boron bromides by reaction with bis(trifluoromethyl)mercury, trichlorofluoromethane, or tribromofluoromethane: Synthesis of BF2B5H8
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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.
- Saulys,Castillo,Morrison
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p. 1619 - 1624
(2008/10/08)
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- 2n framework electron clusters: Diamagnetic polyhedral boron chlorides, BnCln (n = 8-12), from the thermal disproportionation of diboron tetrachloride
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In the presence of elemental mercury, diboron tetrachloride, B2Cl4, is generated from the radio frequency discharge of BCl3 at the rate of 250-350 mg/h. The disproportionation of undiluted B2Cl4 has been examined at a variety of temperatures and found to occur in five stages. The amounts of the polyhedral diamagnetic products, B8Cl8, B9Cl9, B10Cl10, B11Cl11, B12Cl12, and (B9Cl8)2, formed during the reaction are highly dependent upon the thermal history of the sample. In undiluted B2Cl4 the maximum yield of B9Cl9 (29%) occurs at elevated temperatures, 400-450°C, whereas the most B8Cl8 (38%) is produced at 100°C. At temperatures below 100°C, more B12Cl12 than B10Cl10 is observed whereas the reverse is true above 100°C. At ambient temperature the 11B NMR resonances of the polyhedral boron chlorides BnCln (n = 8-12) are all deshielded singlets, 58-78 ppm from BF3·OEt2. The relative thermal stabilities of these compounds, B9Cl9 > B10Cl10 > B11Cl11 > B12Cl12 > B8Cl8, do not correspond to the relative thermal stabilities of 2n + 2 framework electron clusters, such as the borane dianions.
- Davan,Morrison
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p. 2366 - 2372
(2008/10/08)
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