S-Block metal inverse crowns: synthetic and structural synergism in mixed alkali metal-magnesium (or zinc) amide chemistry

This article focuses on the special chemistry that can take place when cert ain lithium (or other heavier alkali metal) amides are combined with certai n magnesium (or zinc) bisamides, Some of the reaction mixtures studied foll ow a straightforward path leading to simple heterobimetallic compositions w ith predictable structures, whereas others take an unexpected turn to behav e as powerful oxygen scavengers or as regioselective bases to yield novel p roducts with unpredictable host-guest macrocyclic structures. We refer to t hese new compounds as 'inverse crown ethers' or 'inverse crowns' because th eir arrangement of Lewis acidic and Lewis basic sites is opposite to that e ncountered in conventional crown ether complexes. This developing phenomeno n appears to be a direct result of pairing together the two distinct metal types in the same complex, as the chemistry cannot be replicated by complex es containing one or the other metal type on its own.