[(CH3)Al(CH2)]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(CH2)(12)] and AlMe3. The existence of cage-like methylaluminomethylene moieties was initially suggested by the reaction of rare-earth-metallocene complex [Cp*Lu-2{(mu-Me)(2)AlMe2}] with excess AlMe3 affording the deca-aluminium cluster [Cp*Lu-4(2)(mu(3)-CH2)(12)Al-10(CH3)(8)] in low yield (Cp*=C5Me5). Treatment of [Ga-8(CH2)(12)] with excess AlMe3 reproducibly gave the crystalline dodeca-aluminium complex [(CH3)(12)Al-12(mu(3)-CH2)(12)] (MAM-12). Revisiting a previous approach to poly(aluminium-methyl-methylene by using a (C5H5)(2)TiCl2/AlMe3 (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.

Automated summary

The molecular structure poly(aluminium-methyl-methylene has been unraveled, and its potential application in organic synthesis, particularly as an efficient methylene transfer reagent for ketones, has been explored.