A new approach to lithium-heavier alkali metal interchange reactions: synthesis of a tetralithium pentasoldium mixed alkoxide-amide dome-shaped cage compound with an encapsulated hydroxide molecule

摘要

An investigation of metal-metal interchange reactions between aklali metal amides and alkali metal alkoxides, relevant to the area of 'superbases', has uncovered a novel adduct containing both components, which has been isolated from solution and crystallogrphically characterised. Formulated as [Li_4Na_4(Bu~tO)_4{PhN(H)}_4(NaOH)(4-Me-py)_4], this tetralithium pentasodium mixed alkoxide-amide can be synthesized either by reaction of lithium anilide with sodium t-butoxide or of sodium anilide with lithium t-butoxide, in the presence of the co-ordinating solvent 4-methylpyridine (4-Me-py). The single sodium hydroxide molecule in the formulation occurs adventitiously, but consistently. X-ray crystallographic studies revceal a 17-vertex dome-shaped structure founded on a (NaN)_4 basal ring, above which lies a smaller (LiO)_4 ring then an apical Na atom: the OH~- ion occupies an internal position within the dome. Discussion focuses on the striking resemblance between this structure and that of the previously reported tetralithium pentapostassium mixed alkoxide-enolate [Li_4K_4(Bu~tO)_4(C_6H_(11)O)_4(KOH)(THF)_5], and it is pointed out tha the dominant factor in their common architecural design appears to be the encapsulated hydroxide molecule