Synthesis and Structures of Hydrazinoalanes and Hydrido(hydrazino)aluminates⋆

Several monomeric dimethylaluminium hydrazide ether adducts Et2O/THF × Me2AlNR–NR′R′′ (5–7) were obtained by deprotonating the respective hydrazines with nBuLi, followed by reaction with Me2AlCl. The hydrazines Ph(H)N–N(SiMe3)2 and tBu(H)N–N(H)SiMe3 react with LiAlH4 in the presence of either ether or THF with the formation of dimeric lithium hydrazino(hydrido)aluminates, e.g. 8 and 9. Their structures depend on the number of acidic hydrogen atoms bonded to the nitrogen atoms of the starting hydrazine. The hydrazine Ph(H)N–N(SiMe3)2 (1) reacts with LiAlH4 to form monometallated LiAlH3[(Ph)N–N(SiMe3)2] × 2 Et2O (8) with elimination of one equivalent of H2. The molecule is dimeric and features an (AlHLiH)2 eight-membered ring. In contrast, the reaction of tBu(H)N–N(H)SiMe3 with LiAlH4 in the presence of THF leads to the formation of dimeric 2 THF × LiAlH2[(tBu)N–N(SiMe3)] (9) with a central (AlNN)2 six-membered ring. A dimeric aluminium hydrazide 10 was obtained by allowing tBu(Li)N–N(H)SiMe3 to react with Me2AlCl in a hexane/toluene solution. The structure of 10 features a six-membered Al2N4 ring in chair conformation.