Aluminates with Fluorinated Schiff Bases: Influence of the Alkali Metal–Fluorine Interactions in Structure Stabilization

Abstract

New heterometallic aluminium-alkali metal compounds have been prepared using Schiff bases with electron withdrawing substituents as ligands. The synthesis of these new species was achieved via the reaction of AlMe3 with the freshly prepared alkali-metallated ligand. The derivatives formed were characterized by NMR in solution and by single crystal X-ray diffraction in the solid state. Aluminate derivatives with lithium and sodium were prepared and a clear influence of the alkali metal in the final outcome is observed. The presence of a Na···F interaction in the solid state has a stabilization effect and the species [NaAlMe3L]2 can de isolated for the first time, which was not possible when using Schiff bases without electron withdrawing substituents as ligands.

Main Group Metal‐Mediated Transformations of Imines

“…Extending Schiff bases into heterobimetallic chemistry,t he Mosquea [51,52] group has synthesised as eries of heterobimetallic aluminates incorporating ab identate imine as al igand.T he first of their class, the phenol-imine is deprotonated in situ by MHMDS( M = Li or K) or NaH at the ortho-hydroxyl group followed by reaction with trimethylaluminium in toluene (Scheme 13). In all complexes, the phenoxo-iminel igand functions as ab identate bridge between the alkali metal and the aluminiuma toms.…”

“…Substitution of the Schiff base with electron‐withdrawing fluorine substituents provides additional stabilising M⋅⋅⋅F interactions (Scheme 14), [52] allowing solid state isolation of the initial sodium aluminate complexes before redistribution in solution. Interestingly, no alkali metal salt (MF) elimination is observed in these reactions, highlighting the stability of the species compared to their pentafluoro‐analogues in which M–F elimination occurs [53] (see section 6).…”