text: The advantage of using ketenyl anion molecule is to synthesize desired compound selectively without concerning dimerization before synthesizing a target product. In ylide-ketenyl anion, electrophile can be substituted in exchange of metal to functionalize the ketene moiety at high yield.  Since the central carbon is negatively charged, this nucleophilicity enable substitution with a series of electrophilic compounds such as triphenylmethyl group. Some ketenyl anion can further react with other compounds to form a new functional group. For example, after electrophilic substitution of ketenyl anion with triphenylmethyl group, the treatment with water results in formation of carboxylic acid at C=O moiety.  Reported compounds from Gessner et al. had more than 90% yield isolated as solid.  
  Not only at the central carbon where a cation can be coordinated, other carbon atom and terminal oxygen atom can also be functionalized upon electrophilic substitution. This reactivity allows activation of chemical bonds such as S-S and C=O bonds and new bonds C-S bond and C=C bond. These products requires CO and substrates of interests, which highlight new synthetic pathways of organic compounds at room temperature instead of extreme conditions such as pyrolysis.  
  A stabilized ketenyl anion also undergoes dimerization with disubstituted phosphine compound to form a heterocyclic product. In this reaction, an intermediate is proposed to be electrophilic substitution of a disubstituted phosphine compound followed by dimerization. 
  In different ketenyl anion compound, cleavage of C-H bond, C=N bond, and I bond at room temperature were also reported in phosphinidene-stabilized ketene. For I cleaving reaction, the mechanism is proposed to be cleavage of the bond at central carbon and migration of I to phosphorus atom.