Cyanoform and Its Isomers. Relative Stabilities, Spectroscopic Features, and Rearrangements by Coupled Cluster and MCSCF-Based Methods

Marek Szczepaniak; Jerzy Moc

doi:10.1021/acs.jpca.6b10951

Cyanoform and Its Isomers. Relative Stabilities, Spectroscopic Features, and Rearrangements by Coupled Cluster and MCSCF-Based Methods

J Phys Chem A. 2017 Feb 16;121(6):1319-1327. doi: 10.1021/acs.jpca.6b10951. Epub 2017 Feb 6.

Authors

Marek Szczepaniak¹, Jerzy Moc¹

Affiliation

¹ Faculty of Chemistry, Wroclaw University , F. Joliot-Curie 14, 50-383 Wroclaw, Poland.

PMID: 28094531
DOI: 10.1021/acs.jpca.6b10951

Abstract

Although an isolation of elusive tricyanomethane HC(CN)₃ was recently reported, the existence of other HC₄N₃ species has yet to be confirmed. In this work, the relative stabilities, spectroscopic features, and rearrangements of tricyanomethane and its four isomers are examined using single- (CCSD(T), CCSD(T)-F12) and multireference (MCSCF, MRPT2) methods. Tricyanomethane and dicyanoketenimine (NC)₂CCNH, which are found to be the two most stable HC₄N₃ isomers lying within 9 kcal/mol, can be discriminated by their spectroscopic parameters. The predicted stepwise interconversion path relating HC(CN)₃ and (NC)₂CCNH features the HC₄N₃ species comprising the C-C-N ring moiety, with the largest barrier being associated with the initial H migration to one of the CN carbons. Adding a water molecule reduces the H migration barrier strongly and makes it possible to interconvert tricyanomethane to dicyanoketenimine in a "concerted" way.