Treacherous Tetrahedron

Abstract

The relative strength of the triple bond in N2 renders compounds with three or more catenated nitrogen atoms unstable, often explosively so. Banert et al. have succeeded in the careful preparation and isolation of the nitrogen-rich, dangerously explosive tetraazidomethane, C(N3)4, as a colorless liquid at room temperature. The stable, readily available trichloroacetonitrile molecule proved the most convenient precursor, affording the product after an 18-hour reaction with sodium azide in acetonitrile solvent. Cycloadducts with three and four equivalents of cyclooctyne could be isolated in ∼5% yield and were characterized crystallographically. Reaction with norbornene, however, yielded unusual tetrazole derivatives in place of expected 1,3-dipolar cycloaddition adducts. Despite the compound's instability, the authors acquired clean 13C and 15N nuclear magnetic resonance spectra, as well as vibrational and mass spectral data, and an estimated boiling point of 165°C. Both Brønsted and Lewis acids accelerated exchange with free azide. — JSY