A New Class of Aluminum Cations Based upon Tetradentate (N₂O₂) Chelating Ligands

Herein are described the synthesis and characterization of the complexes of formula LAIR (where R = Cl and L = Salen (1), SalenCl (2), Acen (3) and where R = Me and L = Salen (4), SalenCl (5), Acen (6); Salen = N,N′-ethylenebis((2-hydroxyphenyl)methylimine), SalenCl = N,N'-ethylenebis((2-hydroxy-5-chiorophenyl)methylimine), Acen = N,N'-ethylenebis((2-hydroxyphenyl)-1-ethylimine)). The LAlCl derivatives dissolve in water and MeOH to yield the cationic complexes [LAl(H₂O)₂]⁺Cl^- (L = Salen (7), SalenCl (8), Acen (9)) and [LAl(MeOH)₂]⁺Cl^- (L = Salen (10), SalenCl (11), Acen (12)), respectively. An alternative preparation of the cationic species involves the reaction of the LAlCl derivative with NaBPh₄. This leads to complexes of formula [LAl(MeOH)₂]⁺BPh₄^- (L = Salen (13), SalenCl (14), Acen (15)). Complexes 4-6 can be reacted with either MeOH or 4-chloro-3,5-dimethylphenol (Ph') to form complexes of general formula LAlOR (R = Me, L = Salen (16), SalenCl (17), Acen (18); R = Ph', L = Salen (19), SalenCl (20), Acen (21)). All of the compounds were characterized by IR, melting points, elemental analyses, and, when soluble, NMR. Additionally, the crystal structures of 7, 13, 15, and 18 were obtained.