An Alternative Approach to Al2O2 Ring Systems by Unexpected Cleavage of Stable Al-F- and Si-O- Bonds †

The reaction of dimethyl aluminum fluoride (Me2AlF, DMAF) with 2,6-diisopropylphenol and triethylcitrate, respectively, leads to the products (RO)6Al4F2Me4 (R = 2,6-i-Pr2C6H3) (1) and (ROAlFMe)2 (R = C(CH2COOEt)2(COOEt)) (2), containing Al2O2 ring systems. Both aluminum-μ-oxo fluorides have been structurally characterized. Fluorine exchange in the reaction of 2,6-diisopropylphenol with DMAF has been monitored using 19F NMR spectroscopy. The proposed processes in solution are confirmed by the solid-state structure of 1. Compound 1 contains four aluminum centers forming three four-membered ring systems. The two outer cycles consist of bridging −OR groups, whereas the aluminum atoms in the central cycle are connected via fluorine atoms. Two of the aluminum atoms are 4-fold coordinated, and two are 5-fold coordinated. Compound 1 contains a rare four-membered Al2F2 ring system. Compound 2 exhibits a dimeric structure, with oxygen rather than fluorine atoms bridging the aluminum atoms. A further carboxy oxygen ...