From graphite and nitrogen to CCN3– in just one step

February 22, 2017

The first experimental realization of the long-sought triply deprotonated acetonitrile anion CCN3– succeeded by a remarkably simple solid state synthesis at moderate conditions (650 °C). CCN3– forms from the usually unreactive elements carbon and nitrogen owing to metal activation. This route is unparalleled in comparison with typical synthetic routes to N-containing organic compounds or carbon nitrides that employ reactive precursors like ammonia for C–N bond-formation.

A team of scientists from MPI for Chemical Physics of Solids and TU Dresden, Germany were able to stabilize the CO2 isoelectronic acetonitriletriide anion CCN3– in the bulk host framework of the Ba5[TaN4][C2N] nitridometalate. The molecular structure of the CCN3– anion was verified by various methods such as NMR and vibrational spectroscopy as well as quantum chemical calculations. Examination of the anion’s bonding situation revealed a shift of the electron pairs towards two double bonds in contrast to the acetonitrile molecule H3C–C≡N.

CCN3– 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 cynamide anions CN22 as well as highly reduced cyano metalates such as [Co(CN)3]6–. Alkaline-earth rich nitridometalates might be a promising “cradle” for more highly charged anions, and the employed synthetic approach could be the basis for a generalized stabilization concept.

PH, FJ / CPfS

Metal activation of graphite and nitrogen leads to the unprecedented acetonitriletriide anion CCN3– stabilized in the nitridometalate Ba5[TaN4][C2N].

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