Group 13 cation formation with a potentially tridentate ligand

A potentially tridentate ligand, Phensal(tBu)H₃, was prepared by the condensation of 1 equiv of phenylenediamine with 3,5-di-tert-butylsalicylaldehyde. When 1 equiv of this new ligand is added to AlMe₃, [[Phensal(tBu)HAlMe]]₂ (1) results. In contrast, this reaction with GaMe₃ produces [Phensal(tBu)H₂]GaMe₂ (2). When 1 or 2 equiv of Phensal(tBu)H₃ is combined with Et₂AlCl, the complex [Phensal(tBu)]₂AlCl (3) forms. However the same reaction with Me₂GaCl leads to [Phensal(tBu)H₂]Ga(Me)Cl (4). A cationic complex, {[Phensal(tBu)]₂Al}⁺Cl^- (5), is formed when 3 is dissolved in MeOH. The MeOH apparently mediates the formation of the cation but does not coordinate the cationic metal. When the solvent is removed, 5 reverts back to neutral 3. When 3 is combined with GaCl₃ in toluene, another cationic complex, {[Phensal(tBu)H₂]₂Al}⁺GaCl₄ ^- (6), is formed. In a similar manner, {[Phensal(tBu)H₂]₂Al}⁺Me₂AlC l₂^- (7) is formed by adding Me₂AlCl to 3. The compounds were characterized by mp, elemental analyses, IR, ¹H and ²⁷Al NMR, and in the case of 2, 5, and 6 single-crystal X-ray analysis.