[(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).

C-H-Bond Activation and Isoprene Polymerization Studies Applying Pentamethylcyclopentadienyl-Supported Rare-Earth-Metal Bis(Tetramethylaluminate) and Dimethyl Complexes.

As previously shown for lutetium and yttrium, 1,2,3,4,5-pentamethylcyclopentadienyl (CMe = Cp*)-bearing rare-earth metal dimethyl half-sandwich complexes [Cp*LnMe] are now also accessible for holmium, dysprosium, and terbium via tetramethylaluminato cleavage of [Cp*Ln(AlMe)] with diethyl ether (Ho, Dy) and tert-butyl methyl ether (TBME) (Tb). C-H-bond activation and ligand redistribution reactions are observed in case of terbium and are dominant for the next larger-sized gadolinium, as evidenced by the formation of mixed methyl/methylidene clusters [(Cp*Ln)(CH)(Me)] and metallocene dimers [Cp*Ln(AlMe)] (Ln = Tb, Gd). Applying TBME as a "cleaving" reagent can result in both TBME deprotonation and ether cleavage, as shown for the formation of the 24-membered macrocycle [(Cp*Gd)(Me)(CHOBu)(AlMe)] or monolanthanum complex [Cp*La(AlMe){MeAl(CH)OBu}] and monoyttrium complex [Cp*Y(AlMe)(MeAlOBu)], respectively.