Neutral and charged group 13–16 homologs of carbones EL₂ (E = B⁻–In⁻; Si–Pb; N⁺–Bi⁺, O²⁺–Te^{2 +})

The review covers experimental and theoretical work on neutral and charged compounds EL₂ (E = B⁻–In⁻; Si–Pb; N⁺–Bi⁺, O^{2 +}–Te^{2 +}) where the ligands L bind to an atom or ion with four valence electrons of the groups 13–16. The molecules are homologs of carbones CL₂, which have been identified as divalent carbon(0) compounds in 2006. Whereas bonding in classical carbones was identified in terms of dative interactions L → C ← L, the homologs exhibit bonds that can be described with single and double electrons or with a mixture of the bonding categories. Much progress has been made in the recent past in this still rapidly developing field. The analysis of the bonding nature and the isolation of new examples of low-valent main-group compounds and their application in catalysis contributed to the fast expansion of knowledge in an exciting area of inorganic chemistry. The chemistry of the lower-valent main groups is a prolific field for theoretical and experimental chemists, constantly yielding surprising discoveries, and it remains a challenge for the inventive chemist.