Synthesis and Structures of Hydrazinoalanes and Hydrido(hydrazino)aluminates

Abstract

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)alummates, 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.