Bis(Aluminyl)Magnesium: A Source of Nucleophilic or Radical Aluminium‐Centred Reactivity

Abstract

AbstractThe homoleptic magnesium bis(aluminyl) compound Mg[Al(NON)]2 (NON=4,5‐bis(2,6‐diisopropylanilido)‐2,7‐di‐tert‐butyl‐9,9‐dimethylxanthene) can be accessed from K2[Al(NON)]2 and MgI2 and shown to possess a non‐linear geometry (∠Al−Mg−Al=164.8(1)°) primarily due to the influence of dispersion interactions. This compound acts a four‐electron reservoir in the reductive de‐fluorination of SF6, and reacts thermally with polar substrates such as MeI via nucleophilic attack through aluminium, consistent with the QT‐AIM charges calculated for the metal centres, and a formal description as a Al(I)−Mg(II)−Al(I) trimetallic. On the other hand, under photolytic activation, the reaction with 1,5‐cyclooctadiene leads to the stereo‐selective generation of transannular cycloaddition products consistent with radical based chemistry, emphasizing the covalent nature of the Mg−Al bonds and a description as a Al(II)−Mg(0)−Al(II) synthon. Consistently, photolysis of Mg[Al(NON)]2 in hexane in the absence of COD generates [Al(NON)]2 together with magnesium metal.