Sandwich-Like Complexes Based on 'All-Metal' (Al42-) Aromatic Compounds

摘要

Designing new chemical compounds is one of the most ambitious goals of every chemist. Nonetheless, efforts made to understand the chemistry of new chemical compounds often yield new paradigms which open unexpected research areas. All-metal aromatic molecules, recently synthesized by Li et al., constitute one such example. Indeed, rationalizing the unexpected large resonance energy of Al_4~(2-) has yielded the concept of multiple-fold aromaticity, present in molecules that possess more than one independent delocalized bonding system, either σ-type or π-type, each of them satisfying the 4n + 2 electron counting rule of aromaticity. This new concept should help one to understand the simultaneous contributions to aromaticity within the same molecular structure as arising from various delocalized bonding systems of the molecule, and it should be of general applicability, irrespective of whether the molecule is organic or inorganic.