Octet-deficient functional groups

thumb|60px|Methylene (compound)|Methylene is the simplest carbene. In organic chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The general formula is or where the R represents substituents or hydrogen atoms.

thumb|115px|right|The generic structure of a nitrene group

Silylene is a chemical compound with the formula SiR2 (R = H). It is the silicon analog of carbene. Silylenes decomposes rapidly when condensed.

Class of reactive intermediate species based on nitrogen and isoeletronic with carbene