The quest for the elusive carbodiimide ion HN C NH + and its generation from ionized cyanamide by proton-transport catalysis

• Published in: Chemical physics letters Vol. 478; no. 4; pp. 144 - 149
• Main Authors: Jobst, Karl J., Gerbaux, Pascal, Dimopoulos-Italiano, Georgina, Ruttink, Paul J.A., Terlouw, Johan K.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 27-08-2009
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2009.07.083

The isomerization of the cyanamide ion (1) into its more stable carbodiimide tautomer (2) by an intramolecular 1,3-H shift is not feasible but a single H
2O molecule catalyzes this reaction in a process termed proton-transport catalysis.
Tandem mass spectrometry based collision experiments and computational chemistry (CBS-QB3/APNO methods) indicate that the elusive carbodiimide ion HN
C
NH
+
is a stable species in the gas-phase. The ion is the most stable of the family of
CH
2
N
2
+
ions and a very high barrier (87
kcal
mol
−1) separates it from its tautomer ionized cyanamide, H
2N−C
N
+
.
The computations also predict that, in the presence of a single H
2O molecule as the catalyst, the cyanamide ion isomerizes into the carbodiimide ion. Experiments on the ion–molecule reaction of H
2N−C
N
+
and H
2O, a reaction of potential interest in astrochemistry, confirm this prediction.