SECONDARY AMINE STABILIZED ALUMINUM HYDRIDES DERIVED FROM N,N'-DI-TERT-BUTYLETHYLENEDIAMINES

The metalation of substituted N,N'-di-tert-butylethylenediamines by va rious aluminum hydride sources has been investigated. HN(t-Bu)CH(t-Bu) CH2N(H)(t-Bu) forms a dimeric lithium chelated adduct of LiAlH4, N(t-B u)CH(t-Bu)CH2N(H)(t-Bu)]Li(mu-H)(2)AlH2}(2)], 4, which thermally decom poses to yield the tetrameric lithium diamidoaluminum hydride [{Li[N(t -Bu)CH(t-Bu)CH2N(t-Bu)]AlH2}(4)], 5. The same diamine reacts with AlH3 .-NMe(3) or AlH3 diethyl etherate to give the secondary amine stabili zed amidoaluminum hydride species [{HN(t-Bu)CH(t-Bu)CH2N(t-Bu)}AlH2], 2. Similarly, the same aluminum hydride sources react with the diamine rac-HN(t-Bu)CH(Me)CH(Me)N(H)(t-B u) to yield [{rac-HN(t-Bu)CH(Me)CH(M e)N(t-Bu)}AlH2], 3. Compounds 2 and 3 are stable with respect to elimi nation of hydrogen to form diamidoaluminum hydrides, but can be conver ted to the alane rich species, [H2Al{N(t-Bu)CH(t-Bu)CH2N(t-Bu)}AlH2], 6, and [H2Al{rac-N(t-Bu)CH(Me)CH(Me)N(t-Bu)}AlH2], 7, by reaction with AlH3 . NMe(3) under special conditions. The varying reactivity of the three aluminum hydride sources in these reactions has enabled mechani stic information to be gathered, and the effect of the different steri c requirements in the diamines on the stability of the complexes is di scussed. Crystals of 3 are monoclinic, space group P2(1)/n (No. 14), w ith a = 8.910(4), b = 14.809(1), and c = 12.239(6) Angstrom, beta = 10 9.76(2)degrees, V = 1520(1) Angstrom(3), and Z = 4. Crystals of 4 are orthorhombic, space group Pbca (No. 61), with a = 15.906(9), b = 24.65 1(7), and c = 9.933(7) Angstrom, V = 3895(3) Angstrom(3), and Z = 4. C rystals of 6 are monoclinic, space group P2(1)/c (No. 14), with a = 8. 392(1), b = 17.513(2), and c = 12.959(1) Angstrom, beta = 107.098(8)de grees, V = 1820.4(3) Angstrom(3), and Z = 4.