New homo- and hetero-alkali metal alkoxide cages;: crystal structures of [Me2N(CH2)2OLi]8 and [{Me2N(CH2)2O}12Li8K6]O

The reaction of N,N'-dimethylaminoethanol (DMAEH), (Me)(2)N(CH2)(2)OH, with (BuLi)-Bu-n and (BuLi)-Bu-n/(BuK)-Bu-n respectively results in the formation of the homo- and hetero-metallic alkoxides [(MeN)-N-2(CH2)(2)OLi](8), 1, and [{Me2N(CH2)(2)O}(12)Li8K6]O, 2, rather than mixed alkyl-alkoxide species. From single crystal X-ray diffraction studies the two complexes are shown to be highly aggregated cage structures. Complex 1 (monoclinic, C2/c) adopts a rare octameric structure constructed from a ring stacked hexamer fused with a (LiO)(2) dimer creating a sixteen vertex Li-O cluster. Complex 2, which crystallises (rhombohedral, R (3) over bar) with thf and cyclohexane molecules in the lattice, forms a highly symmetrical, almost spherical, cage with an unprecedented Li:K ratio of 8:6.