The acetonitriletriide anion CCN^3– is the fully deprotonated form of acetonitrile and is isoelectronic to CO₂. Michael Ruck and Eike Brunner, TU Dresden, Germany, and Peter Höhn, MPI for Chemical Physics of Solids, Germany, and their coworkers stabilized CCN^3– in the bulk host framework of a Ba₅[TaN₄][C₂N] nitridometalate via a one-pot synthesis from the elements under moderate conditions (650 °C). This route is unparalleled; typical synthetic routes to N-containing organic compounds or carbon nitrides use reactive precursors like ammonia for C–N bond-formation

The molecular structure was verified by various methods such as NMR and vibrational spectroscopy as well as quantum chemical calculations. In contrast to acetonitrile (H₃C−C≡N), the electron pairs of CNN^3– are shifted towards two double bonds, that is, [C=C=N]³⁻.

CCN^3– is the most recent example of electron-rich anions being stabilized within a combined framework of a nitridometalate structure and alkaline-earth cations. Other examples include cyanamide anions CN₂^2– as well as highly reduced cyano metalates such as [Co(CN)3]^6–. According to the researchers, their work might pave the way to more examples of highly charged anions as well as to a general stabilization concept.

• The Triply Deprotonated Acetonitrile Anion CCN³⁻ Stabilized in a Solid,
  Franziska Jach, Stephan Ingmar Brückner, Alexander Ovchinnikov, Anna Isaeva, Matej Bobnar, Matthias Friedrich Groh, Eike Brunner, Peter Höhn, Michael Ruck,
  Angew. Chem. Int. Ed. 2017.
  DOI: 10.1002/anie.201611177