Investigation of the chemistry of amine-boranes : B-halogenation reactions of N,N,N',N'-tetramethylethylenediamine-bisborane and chemical properties of ammonia-borane



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N,N,N',N',-tetramethylethylenediamine-bisborane (TMED[dot]2BH[lowered 3]) has been treated with HF, HC1, HBr, and Br[lowered 2] and the reactions monitored with [raised 1]H NMR. The new compounds TMED[dot]2BH[lowered 2]X (X = F, Cl, Br) and TMED[dot]2BHX[ lowered 2] (X = Br) were isolated and characterized. The course of halogen substitution is believed to reflect the influence of an inductive effect in agreement with an earlier study. The probable mechanism of halogenation is discussed. Ammonia-borane (H[lowered 3]N[dot]BH[lowered 3]) has been synthesized by a modification of a previously reported synthesis and the deutero-ammonia-borane derivatives (H[lowered 3]N[dot]BD[lowered 3] and D[lowered 3]N[dot]BD[lowered 3]) have also been synthesized via new approaches. Reactions of ammonia-borane and boron trihalides (BF[lowered 3], BCl[lowered 3] and BBr[lowered 3]) in diethyl ether have been studied by using [raised 11]B NMR. In the case of BCl[lowered 3] and BBr[lowered 3], hydrogen-halogen exchange reactions took place and the new compounds H[lowered 3]N[dot]BH[lowered 2]X(X = Cl, Br) and H[lowered 3]N[dot]BHX[lowered 2] (X = Cl) were formed and identified. In the case of BF[lowered 3], a Lewis acid displacement reaction took place instead, resulting in the formation of H[lowered 3]N[dot]BF[lowered 3], and H[lowered 2]NB[lowered 2]H[lowered 5]. Mechanisms of these reactions are proposed. The thermal decomposition of ammonia-borane has been studied by instrumental thermal analyses and decomposition product measurements.