Multiple deprotonation of primary aromatic diamines by LiAlH4

Abstract

Reaction of LiAlH₄ with 1,2-phenylenediamine (1H₄) in THF results in formation of the metallocyclic amido-/imido complex [{Al(1H₂)}₂{Al(1H)₂}₂][Li(THF)₂]₄ (3), while in the presence of various Lewis base ligands 1,8-diaminonaphthalene (2H₄) gives the amido-(‘ate’) complexes [Al(2H₂)₂]⁻[Li(LL′)]⁺ [L = THF, L′ = PMDETA (N,N,N′,N′,N′′-pentamethyldiethylenetriamine) (4); L = L′ = TMEDA (N,N,N′,N′-tetramethylethylenediamine) (5)]. The latter complexes provide evidence of intermediates in the proposed reaction pathway for formation of the cyclic framework of the tetraanion [{Al(1H₂)}₂{Al(1H)₂}₂]⁴⁻ of 3.