Modern ate chemistry: Applications of synergic mixed alkali-metal-magnesium or -zinc reagents in synthesis and structure building

The special synergic reactivity exhibited by certain heterobimetallic ate compounds in which magnesium or zinc is paired together with an alkali metal such as lithium, sodium, or potassium provides the theme of this review. The emerging concepts of alkali-metal-mediated magnesiation and alkali-metal-mediated zincation are introduced with respect to the selective deprotonation and/or polydeprotonation of a series of arene, aromatic heterocyclic, metallocene, and metal pi-arene substrates. It is shown that, in accomplishing such deprotonations, alkali metal-magnesium amide based reagents can often generate "inverse crown" ring compounds. Inverse crowns display polymetallic cationic "host" rings (residue of the reacted mixed-metal base) surrounding an anionic "guest" (the deprotonated substrate) in a Lewis acidic-Lewis basic arrangement inverse to that encountered in conventional crown ether complexes. A signature feature of inverse crown ring and related mixed-metal structures is a synergic combination of Mg-C (or Zn-C) sigma bonds and alkali-metal-pi contacts. Also included are related inverse crown ether complexes in which the guest can be an oxo, peroxo, hydrido, alkoxo, or enolato anion and the first example of the concept of synergic nucleophilic addition involving the action of a new sodium dialkylamidozincate reagent toward benzophenone.