Generation and spectroscopic identification of ClCNS, ClNCS and NCCNS

The photolysis of four chloro-substituted thiadiazoles (3,4-dichloro-, 3-chloro-and 3-chloro-4-fluoro-1,2,5-thiadiazole; 3,5-dichloro-1,2,4- thiadiazole) and 3,4-dicyano-1,2,5-thiadiazole was investigated in inert solid-argon matrices at cryogenic temperatures by means of UV irradiation at selected wavelengths of 254 and 280 nm. The photolysis products were identified by mid-IR and UV spectroscopy. Evidence for the existence of three novel pseudohalides, namely, chloronitrile sulfide (ClCNS), chlorine isothiocyanate (ClNCS) and cyanogen N-sulfide (NCCNS), was provided by direct spectroscopic methods supported by quantum chemical calculations. Ground-state geometries, vibrational frequencies, IR intensities, and UV excitation energies of ClCNS, ClNCS and NCCNS were obtained from calculations using the B3LYP, CCSD(T) and SAC-CI methods and the aug-cc-pV(T+d)Z basis set. Three novel pseudohalides, namely, chloronitrile sulfide (ClCNS), chlorine isothiocyanate (ClNCS) and cyanogen N-sulfide (NCCNS) were generated by photolysis of chloro-substituted thiadiazoles in low-temperature, solid-argon matrices and studied by UV and IR spectroscopy (see figure) and quantum chemical calculations.