Tetrylones: An Intriguing Class of Monoatomic Zero-valent Group14 Compounds

Tetrylones (ylidones) represent a class of zero-valent group14 compounds with the general formula EL2 (E=C, Si, Ge, Sn, or Pb; L=neutral sigma-donating ligand), wherein the tetrel atom, E(0), possess its four valence electrons in the form of two electron lone pairs, and is moreover coordinated by two ligands (L) via donor-acceptor interactions (L <- E <- L). This review focuses on the synthesis, structure, reactivity, and computational examination of the isolable heavier tetrylones (Si, Ge, Sn) that have been discovered recently. A comprehensive review on carbone chemistry is beyond the scope of this review. It should also be noted that tetrylones contain two different types of lone pairs, that is, one that exhibits p-type and one that exhibits s-type characteristics. Different behavior should thus be expected when these lone pairs react with Lewis acids.