- Lewis acid-base reactions among dimethylaminoboron hydrides
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The dimethylaminoboron hydrides related to diborane form a system of Lewis acids and bases, the interconversion of which can be described as addition or removal of BH3 groups. The first-stage action of [(CH3)2N]3B to remove BH3 from (CH3)3N· BH3 is not appreciably reversible, but the second stage, in which [(CH3)2N]2BH and (CH3)3N·BH3 form 2(CH3)2NBH2 and (CH3)3N, is reversible with ΔF° = 13.95 - 0.0330T kcal. Our base·(CH3)2NB2H5 adducts show vapor-phase dissociation increasing in the order pyridine, (CH3)3P, 2-methylpyridine, (CH3)3N; and (CH3)2PH·(CH3)2NB 2H5 fails to exist in the vapor phase but forms a partially dissociated liquid. All five of these adducts on heating react further to form (CH3)2NBH2 and base·BH3, without reversal. The adducts CH3PH2·(CH3)2NB 2H5 and (CH3)2PCF3·(CH3) 2NB2H5 are still more easily dissociated, and their conversion to BH3 complexes and (CH3)2NBH2 is reversible with ΔF° = 10.61 - 0.0268T and 6.59 - 0.01943T kcal., respectively. It is quite apparent that diborane is a much stronger Lewis acid than (CH3)2NB2H5.
- Burg, Anton B.,Sandhu, Jagtar S.
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- Reactions of boron hydrides with the iminium salt [Me2NCH2]I. Synthesis and characterization of 1-X-μ-(Me2NCH2)B5H7 (X = H, C2H5, Br), a new class of bridge-substituted pentaborane derivatives
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Reactions of [Me2NCH2]I (1) with salts of the B5H8-, 1-(C2H5)B5H7-, and 1-BrB5H7- anions produce the μ-((dimethylamino)methyl)pentaborane derivatives μ-(Me2NCH2)B5H8, 1-(C2H5)-μ-(Me2NCH2)B 5H7, and 1-Br-μ-(Me2NCH2)B5H7, respectively, in good yields. A structure for these compounds is proposed in which a bridging hydrogen atom of B5H9 has been replaced by a C-N two-atom bridge, the Me2NCH2 group. These clusters are analogues of the arachno-B5H10- anion, and there is no evidence of direct bonding between the Me2NCH2-bridged boron atoms. Reaction of 1 with NaBH4 forms Me3N·BH3, while reaction with [Me4N][B3H8] produces a variety of products including Me3N·BH3, Me3N·B3H7, B2H6, and B5H9. Attack of 1 on B5H9 occurs slowly at 65°C, forming Me3N·BH3 and Me3N·B3H7.
- Gaines, Donald F.,Coons, Darrell E.
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p. 364 - 367
(2008/10/08)
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- Matrix isolation-mass spectroscopy study of the reaction of boron trifluoride with trimethylamine-aiane and trimethylamine-gallane
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The gas-phase reactions of BF3 with (CH3)3N·AlH3 and (CH3)3N·GaH3 were studied with a combination matrix isolation-infrared spectrometer-mass spectrometer apparatus. The initial reaction products were BF2H and N(CH3)3; no AlH3 or GaH3 was detected. The reaction is a halide-hydride exchange and not a Lewis acid displacement reaction. The previously reported reaction of BF3 with (CH3)3N·GaH3 to produce uncoordinated gallium hydride in both the gas and condensed phases was not observed. A reaction mechanism is proposed to account for the reactions in both phases.
- Shirk, Amy E.,Shirk, James S.
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