Tricyanomethane and Its Ketenimine Tautomer: Generation from Different Precursors and Analysis in Solution, Argon Matrix, and as a Single Crystal

• Published in: Angewandte Chemie International Edition Vol. 56; no. 32; pp. 9582 - 9586
• Main Authors: Banert, Klaus, Chityala, Madhu, Hagedorn, Manfred, Beckers, Helmut, Stüker, Tony, Riedel, Sebastian, Rüffer, Tobias, Lang, Heinrich
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01-08-2017
• Edition: International ed. in English
• Subjects: Argon; azides; Crystals; cyanides; cyanoform; Diethyl ether; Dilution; Evaporation; Infrared spectroscopy; Irradiation; ketenimines; Low temperature; Magnetic resonance spectroscopy; Molecular structure; NMR spectroscopy; Potassium; Precursors; reactive intermediates; Single crystals; Spectroscopic analysis; Spectrum analysis; Sublimation; Sulfuric acid; Temperature effects; X-ray diffraction; cyanoform; azides; reactive intermediates; cyanides; ketenimines
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201704561

Solutions of azidomethylidenemalononitrile were photolyzed at low temperatures to produce the corresponding 2H‐azirine and tricyanomethane, which were analyzed by low‐temperature NMR spectroscopy. The latter product was also observed after short thermolysis of the azide precursor in solution whereas irradiation of the azide isolated in an argon matrix did not lead to tricyanomethane, but to unequivocal detection of the tautomeric ketenimine by IR spectroscopy for the first time. When the long‐known “aquoethereal” greenish phase generated from potassium tricyanomethanide, dilute sulfuric acid, and diethyl ether was rapidly evaporated and sublimed, a mixture of hydronium tricyanomethanide and tricyanomethane was formed instead of the previously claimed ketenimine tautomer. Under special conditions of sublimation, single crystals of tricyanomethane could be isolated, which enabled the analysis of the molecular structure by X‐ray diffraction.
Held incommunicado in an argon matrix, a long‐sought ketenimine was detected after irradiation of an appropriate vinyl azide whereas photolysis or thermolysis of the same precursor in solution led to cyanoform, which is also available as single crystals from potassium tricyanomethanide.