Synthetic and structural developments in hetero-s-block-metal chemistry: new ring-laddering, ring-stacking and other architectures

Hetero-alkali metal organic compounds are of interest because they can exhibit superior reactivity to conventional organolithium reagents. Structurally well-defined mixed lithium–sodium and mixed lithium–sodium–potassium compositions, based on a variety of organic ligands, are surveyed here. A complicated assortment of architectures with lithium-rich, sodium-rich, or equimolar metal stoichiometries is revealed. These structures are analysed with respect to the ‘ring-laddering’ and ‘ring-stacking’ concepts used previously in the rationalisation of organolithium structures. Important homometallic structures, which have appeared since these concepts were reviewed, are also included. Finally, an intriguing new class of mixed lithium–magnesium amide, based around an oxo or peroxo core, is described.