Reactivity studies of AlMe2Cl with potentially tridentate O,N,L-type ligands

• Reactions of tridentate O,N,L-type ligands with AlMe2Cl are described.
• The ligand plays an important role in the formation of cationic derivatives.
• Me2AlCl can act as a fast and effective chloride abstraction agent.
• Structurally characterized tetrahedral cationic aluminium complex.

Neutral tridentate O,N,L-type ligands aeimp-H, quimp-H and ppimp-H (aeimp-H = 2-((dimethylamino)ethylimino)methyl)-4,6-di-tert-butyl-phenol; quimp-H = 2-((quinolin-8-ylimino)methyl)-4,6-di-tert-butyl-phenol; ppimp-H = 2-((2-phenoxyphenylimino)methyl)-4,6-di-tert-butylphenol) readily reacted with AlMe2Cl to afford the corresponding methyl-chloro aluminium derivatives (aeimp)AlMeCl (2a) (quimp)AlMeCl (2b) and (ppimp)AlMeCl (2c) with concomitant elimination of methane. DFT calculations suggested that the pendant donor arm in these species is weakly bounded to the metal centre. A fast chloride abstraction by Me2AlCl from the neutral derivatives 2a and 2b produced the tetrahedral cationic species (η3-O,N,L)AlMe+ counterbalanced by the Me2AlCl2- anion. Analogously direct treatment of bpzmp-H (bpzmp-H = 2,4-di-tert-butyl-6-(bis(3,5-dimethylpyrazol-1yl)methyl)phenol) with two equivalents of Me2AlCl afforded the Al cation [(bpzmp)AlMe][Me2AlCl2] (3d) as determined by single crystal X-ray analysis.

The reaction of tridentate O,N,L-type ligands with AlMe2Cl affords neutral or cationic aluminium derivatives. A cost effective strategy for the synthesis of cationic aluminium complexes is provided.Figure optionsDownload as PowerPoint slide