Chasing Multiple Bonding Interactions between Alkaline-Earth Metals and Main-Group Fragments.

Formally dianionic ligands such as alkylidenes or organoimidos play a major role in the organometallic chemistry of transition metals and are an emerging topical area of f-element chemistry. The pursuit and development of main-group-metal congeners has been tackled sporadically but is clearly lacking behind. The pronounced ionic bonding in particular, prevailing in alkali and alkaline-earth (Ae) metal derivatives, proved cumbersome. Recent substantial progress in the respective field of divalent Ae chemistry has been triggered by the implementation of new synthesis strategies involving new AeII precursors and tailor-made ligands. The main emphasis of this Minireview will be on the synthesis and reactivity of well-defined Group 2 alkylidenes, organoimides, silylenes, and phosphandiides.