Reaction of the Primary Alane (2,4,6-t-Bu(3)H(2)C(6)AlH(2))(2) with Nitriles, Isonitriles, and Primary Amines

The reactions of the sterically encumbered primary alane (MesAlH(2))(2) (Mes = C(6)H(2)-2,4,6-t-Bu(3)) with the nitriles t-BuCN, MesCN (Mes = C(6)H(2)-2,4,6-Me(3)) or MeCN lead eventually to dimeric amido alane products in which one of the ortho t-Bu groups of the Mes ligand is metalated and the nitrile is reduced to the amide ligand N(H)CH(2)R (R = t-Bu, Mes, or Me). The compounds (R = t-Bu, 2 (cis), 3 (trans); Mes, 4 (cis), 5 (trans); Me, 6 (cis)) have been isolated and characterized spectroscopically and also by X-ray crystallography in the cases of 4 and 5. The intermediate, dimeric iminato complex [MesAl(H){&mgr;(2)-NC(H)t-Bu}](2) (1), can also be isolated under carefully controlled, mild conditions. Reaction of (MesAlH(2))(2) with the isonitrile t-BuNC affords the cyclic species {MesAlN(t-Bu)CH(2)}(2) (7) featuring a six-membered (AlNC)(2) ring which, when heated, affords the cyclometalated species (8). Recognition that the products 2-6 and 8 were derivatives of primary amides led to an investigation of synthetic approaches to these product types via the direct reaction of (MesAlH(2))(2) with some primary amines. Treatment of (MesAlH(2))(2) with H(2)NCH(2)Mes affords the dimeric amido alane [Mes(H)Al{&mgr;(2)-N(H)CH(2)Mes}](2) as a mixture of trans (9) and cis (10) isomers. Further heating of 9 and 10 affords the ortho-metalated compounds 4 and 5. The reaction of (MesAlH(2))(2) with H(2)NSiPh(3) furnishes the bis amido aluminum compound MesAl{N(H)SiPh(3)}(2) (11) and [Mes(H)Al{N(H)SiPh(3)}](2). The latter yields the dimeric imide {MesAlNSiPh(3)}(2) (12) at elevated temperature.