Reactions of hydrazine with main group Lewis acids

Hydrazine is reacted with main group Lewis acids including those with LUMOs derived from either vacant p-orbitals, or low lying σ* orbitals and of varying Lewis acidities. This is shown to give a diverse range of resulting products. For Lewis acids with vacant 2p-orbitals such as the boranes, BF₃, Mes₂BH, MesBH₂, PhBBN, and C₆F₅BBN reacts with hydrazine gave the Lewis acid-base mono- and bis-adducts (F₃B)₂(N₂H₄) 1, Mes₂BH(NH₂NH₂) 2, MesBH₂(NH₂NH₂) 3, (PhBBN)₂(NH₂NH₂) 4, and (C₆F₅BBN)NH₂NH₂5, respectively. In contrast, the reaction of the 3p-Lewis acid [Et₃Si(HSiEt₃)]⁺ showed no evidence of Si-hydrazine coordination. Rather, the hydrazinium salt [(NH₂NH₂)₂H][B(C₆F₅)₄] 6 was obtained and prepared independently via reaction with triflic acid and subsequent anion exchange. Reaction of GaCl₃ (a 4p-Lewis acid) with hydrazine afforded the polymeric species [Cl₃GaNH₂NH₂]_n7. The phosphonium bromides [R₃PBr]Br (R = Ph, Et) are σ*-derived Lewis acids and react with hydrazine to afford the salts, [Ph₃PNHNH₂]Br 8 and [(Ph₃PNH)₂]X₂ (X = Br 9, GaCl₄10) and [(Et₃PNH)₂]Br₂11 respectively. In contrast, the corresponding reaction of [(C₆F₅)₃PCl]Cl afforded (H₂NNHC₆F₄)₃PO 12 which exhibited an extended H-bonding network structure in the solid state. These products of the reactions of Lewis acids with hydrazine are documented and the range of structural features discussed.