[(CH )Al(CH )] : 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 (CH ) ] and AlMe . The existence of cage-like methylaluminomethylene moieties was initially suggested by the reaction of rare-earth-metallocene complex [Cp* Lu{(μ-Me) AlMe }] with excess AlMe affording the deca-aluminium cluster [Cp* Lu (μ -CH ) Al (CH ) ] in low yield (Cp*=C Me ). Treatment of [Ga (CH ) ] with excess AlMe reproducibly gave the crystalline dodeca-aluminium complex [(CH ) Al (μ -CH ) ] (MAM-12). Revisiting a previous approach to "poly(aluminium-methyl-methylene" by using a (C H ) TiCl /AlMe (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.