[(CH(3))Al(CH(2))](12): Methylaluminomethylene (MAM‐12)

The molecular structure of enigmatic “poly(aluminium‐methyl‐methylene)” (first reported in 1968) has been unraveled in a transmetalation reaction with gallium methylene [Ga(8)(CH(2))(12)] and AlMe(3). The existence of cage‐like methylaluminomethylene moieties was initially suggested by the reaction of rare‐earth‐metallocene complex [Cp*(2)Lu{(μ‐Me)(2)AlMe(2)}] with excess AlMe(3) affording the deca‐aluminium cluster [Cp*(4)Lu(2)(μ (3)‐CH(2))(12)Al(10)(CH(3))(8)] in low yield (Cp*=C(5)Me(5)). Treatment of [Ga(8)(CH(2))(12)] with excess AlMe(3) reproducibly gave the crystalline dodeca‐aluminium complex [(CH(3))(12)Al(12)(μ (3)‐CH(2))(12)] (MAM‐12). Revisiting a previous approach to “poly(aluminium‐methyl‐methylene” by using a (C(5)H(5))(2)TiCl(2)/AlMe(3) (1 : 100) mixture led to amorphous solids displaying solubility behavior and spectroscopic features similar to those of crystalline MAM‐12. The gallium methylene‐derived MAM‐12 was used as an efficient methylene transfer reagent for ketones.