The reaction of diethylaluminum hydride with the hydrazine derivatives 1-aminopyrrole and 1- aminopiperidine afforded the corresponding dialkylaluminum hydrazides (1 and 2) by the release of elemental hydrogen. Both products are dimeric in the solid state. While 1 adopts a cis arrangement of the pyrrole groups, a trans configuration was determined for the piperidine compound 2. Only 1 gives an equilibrium mixture of cis and trans isomers in solution. Similar compounds (3 and 4) were obtained by the treatment of the same hydrazines with di(tert-butyl)gallium hydride. Both products exhibit the trans configuration in the solid state, but interestingly only the piperidine derivative 4 shows a cis/trans equilibrium in solution.
Treatment of tetramethylpyrazole, N2C3Me4, with equimolar quantities of di(tert-butyl)aluminum hydride leads to the addition of an Al-H bond to one of the C=N double bonds. The dimeric product (1) contains a central six-membered Al2N4 ring in which two tBu2Al+ units are bridging two N2C3 heterocycles. In the zwitterionic, non-centrosymmetric compound one aluminum atom is coordinated by two imino nitrogen atoms, while the second one is bonded to two amide nitrogen atoms. No double hydroalumination occurs upon treatment of tetramethylpyrazole with two equivalents of the hydride. Instead, an adduct (2) of the monomeric hydroalumination product with di(tert-butyl)aluminum hydride was isolated in which the two aluminum atoms are connected by a 3c-2e Al-H-Al bond. A unique trinuclear compound (3) is obtained upon reaction of tetramethylpyrazole with an excess of the sterically less shielded diethylaluminum hydride. It contains two different N2C3 heterocycles: One still contains a C=N double bond similar to that in compounds 1 and 2, while the second one is completely reduced by double hydroalumination to give a saturated heterocycle. The two rings are bridged by three AlEt2 groups. Deprotonation results upon treatment of 3,5-diphenylpyrazole, N2C3H2(C6H5)2, with di(tert-butyl)aluminum hydride.
Treatment of [5]trovacenylethyne, (η 7 -C 7 H 7 )V(η 5 -C 5 H 4 -C≡C-H) (1) with dialkylelement hydrides R 2 E-H (2: E = Al, R = tBu; 3: E = Ga, R = Et; 4: E = Ga, R = tBu) afforded the corresponding alkynyl-dialkylelement compounds by the release of dihydrogen. The paramagnetic compounds 2 to 4 are dimeric in the solid state with the terminal, anionic carbon atoms of the C≡C triple bonds in the bridging
The heterocyclic hydrazine derivatives N-aminopyrrole, H2N-NC4H4, and N-aminopiperidine, H2N-NC5H10, reacted with the hydrides H-Al(CMe3)2 or GaH3NMe2Et by the release of elemental hydrogen and the formation of the corresponding aluminum and gallium hydrazides. These products are dimerized in the solid state via Al-N-Al or Ga-N-Ga bridges and possess four-membered E2N2 heterocycles with two exocyclic N-N bonds.
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