Cyanoisocyanoacetylene, N≡C-C≡C-N≡C.

Vacuum pyrolysis of the precursor complex [(CO)5 Cr(CN-CCl=CF-CN)] resulted in the isolation and structure elucidation by molecular spectroscopy of isomer 1. According to ab initio calculations 1 is 109 kJ mol-1 less stable than NC-C≡C-CN, which has been known for some time. An accurate equilibrium structure for 1 has been determined with mixed experimental and theoretical methods.