Structural and synthetic insights into the chemistry of lithium tetraorganozincates

Main group bimetallic complexes have emerged as powerful reagents in organometallic synthesis, exhibiting unique reactivity profiles that cannot be replicated by their homo-metallic components. This chapter focusses on a particular family of bimetallic reagents, namely higher order lithium zincates. Exhibiting the empirical formulation R4ZnLi2 (R = alkyl, aryl, alkynyl, etc.), these compounds have found widespread applications in cornerstone organic reactions such as deprotonative metalation, metal halogen exchange or C[sbnd]C bond forming processes. By switching on bimetallic cooperativity these reagents exhibit excellent functional group tolerance and regioselectivities while being kinetically activated in comparison with parent organozinc reagents R2Zn. Showcasing key selected examples here we provide an overview on the synthesis, structure, solution constitution and stability of these mixed lithium/zinc complexes and discuss their most representative applications in modern organic synthesis. A main aim of this chapter is to shed light on the close interplay between structure and reactivity in this family of mixed lithium/zinc reagents and how bimetallic cooperation can be maximized to develop more effective and regioselective synthetic protocols.