The Reaction of LiAlH(4) with 1,4-Di-tert-butyl-1,4-diazabutadiene: Imine-Containing Aluminum Hydrides Stabilized by Lithium Coordination.

The reaction of 1,4-di-tert-butyl-1,4-diazabutadiene, 1, with purified LiAlH(4) (free from Al metal) in diethyl ether has been investigated in detail, and a range of products have been isolated. The lithium diamidoaluminum dihydride [Li{N(t-Bu)CHCH(2)N-t-Bu}(2)AlH(2)], 2, the dimeric diamidoaluminum hydride [cis-{[&mgr;-N(t-Bu)CH(2)CH(2)N-t-Bu]AlH}(2)], 3, or the heteroleptic lithium tetraamidoaluminum species [(Et(2)O)Li{N(t-Bu)CH(2)}(2)(CHN-t-Bu)(2)Al], 4, can be selectively obtained depending on the order of addition or stoichiometry of the reactants. We have rationalized these results in terms of the unstable adducts which are likely to be present in solution at low temperature. The X-ray crystal structures of 2 and the dimeric lithium aluminum hydride adduct [{[HN(t-Bu)CH(t-Bu)CHN-t-Bu]Li(&mgr;-H)(2)AlH(2)}(2)], 7, are described.

Aluminum Amides Derived from Metalation of N,N'-Bis(trimethylsilyl)ethylenediamine.

The reaction of N,N'-bis(trimethylsilyl)ethylenediamine with H(3)Al.NMe(3) gives products based on metalation (H(2) elimination), [{[CH(2)N(SiMe(3))](2)AlH}(2)] (1) and [{CH(2)N(SiMe(3))}(2)AlN(SiMe(3))CH(2)CH(2)N(H)SiMe(3)] (2), as well as products derived from N-Si bond cleavage and metalation, [{[CH(2)N(SiMe(3))](2)AlH}(2){HAlN(SiMe(3))CH(2)CH(2)NAlH(2)}] (4) and [H(2)Al{CH(2)N(SiMe(3))}(2)AlN(SiMe(3))CH(2)CH(2)NAl(H)(2).NMe(3)}] (5). Similarly, [Me(3)SiN(H)CH(2)CH(2)N(SiMe(3))AlCl(2)] (3) was isolated as the redistributed/metalated product from the reaction of the same diamine with H(2)Al(Cl).NMe(3). The following crystal data were obtained: (1) monoclinic, space group P2(1)/c (No. 14), a = 13.636(4) Å, b = 9.565(3) Å, c = 22.683(4) Å, beta = 105.67(2) degrees, Z = 4; (2) monoclinic, space group C2/c (No. 15), a = 31.887(3) Å, b = 10.145(6) Å, c = 17.718(3) Å, beta = 100.36(1) degrees, Z = 8; (3) triclinic, space group P&onemacr; (No. 2), a = 11.762(3) Å, b = 11.927(3) Å, c = 7.288(2) Å, alpha = 107.46(2) degrees, beta = 95.29(2) degrees, gamma = 110.41(2) degrees, Z = 2; (4) triclinic, space group P&onemacr; (No. 2), a = 13.884(4) Å, b = 15.379(4) Å, c = 11.044(2) Å, alpha = 102.11(2) degrees, beta = 103.85(2) degrees, gamma = 109.28(2) degrees, Z = 2; (5) triclinic, space group P&onemacr; (No. 2), a = 10.925(5) Å, b = 11.060(5) Å, c = 12.726(4) Å, alpha = 92.38(3) degrees, beta = 95.67(2) degrees, gamma = 96.90(2) degrees, Z = 2.

Secondary Amine Stabilized Aluminum Hydrides Derived from N,N'-Di-tert-butylethylenediamines.

The metalation of substituted N,N'-di-tert-butylethylenediamines by various aluminum hydride sources has been investigated. HN(t-Bu)CH(t-Bu)CH(2)N(H)(t-Bu) forms a dimeric lithium chelated adduct of LiAlH(4), [{[HN(t-Bu)CH(t-Bu)CH(2)N(H)(t-Bu)]Li(&mgr;-H)(2)AlH(2)}(2)], 4, which thermally decomposes to yield the tetrameric lithium diamidoaluminum hydride [{Li[N(t-Bu)CH(t-Bu)CH(2)N(t-Bu)]AlH(2)}(4)], 5. The same diamine reacts with AlH(3).NMe(3) or AlH(3) diethyl etherate to give the secondary amine stabilized amidoaluminum hydride species [{HN(t-Bu)CH(t-Bu)CH(2)N(t-Bu)}AlH(2)], 2. Similarly, the same aluminum hydride sources react with the diamine rac-HN(t-Bu)CH(Me)CH(Me)N(H)(t-Bu) to yield [{rac-HN(t-Bu)CH(Me)CH(Me)N(t-Bu)}AlH(2)], 3. Compounds 2 and 3 are stable with respect to elimination of hydrogen to form diamidoaluminum hydrides, but can be converted to the alane rich species, [H(2)Al{N(t-Bu)CH(t-Bu)CH(2)N(t-Bu)}AlH(2)],6, and [H(2)Al{rac-N(t-Bu)CH(Me)CH(Me)N(t-Bu)}AlH(2)], 7, by reaction with AlH(3).NMe(3) under special conditions. The varying reactivity of the three aluminum hydride sources in these reactions has enabled mechanistic information to be gathered, and the effect of the different steric requirements in the diamines on the stability of the complexes is discussed. Crystals of 3are monoclinic, space group P2(1)/n (No. 14), with a = 8.910(4), b = 14.809(1), and c = 12.239(6) Å, beta = 109.76(2) degrees, V = 1520(1) Å(3), and Z = 4. Crystals of 4 are orthorhombic, space group Pbca (No. 61), with a = 15.906(9), b = 24.651(7), and c = 9.933(7) Å, V = 3895(3) Å(3), and Z = 4. Crystals 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) Å, beta = 107.098(8) degrees, V = 1820.4(3) Å(3), and Z = 4.