posted on 2013-03-21, 00:00authored byLuis A. Ramos, Sonia
E. Ulic, Rosana M. Romano, Mauricio F. Erben, Yury V. Vishnevskiy, Christian G. Reuter, Norbert W. Mitzel, Helmut Beckers, Helge Willner, Xiaoqing Zeng, Eduard Bernhardt, Maofa Ge, ShengRui Tong, Carlos O. Della Védova.
Chlorocarbonylthio-
and isothiocyanate (ClC(O)SCN and ClC(O)NCS)
have been isolated and characterized by IR (Ar matrix, gas), Raman
(liquid), 13C NMR and UV–visible spectroscopies.
Vibrational and quantum chemical studies suggest the presence of the syn and anti conformers (SCN group with
respect to the CO bond) in the gas phase for both constitutional
isomers. syn-ClC(O)SCN is preferred by ΔH° (anti/syn) = 1.3(0.3) kcal mol–1. The solid-state structure of ClC(O)SCN has been
determined by single crystal X-ray diffraction analysis at low temperature.
The crystalline solid consists exclusively of molecules in the syn conformation. On the other hand, the anti form is more stable for the ClC(O)NCS isomer. The structure of ClC(O)NCS
and its conformational composition were determined by gas electron
diffraction. An unusual low syn → anti interconversion energy barrier of 0.98 (0.15) kcal
mol–1 was detected for ClC(O)NCS at cryogenic temperatures.
The photochemistry of both constitutional isomers isolated in solid
argon at 15 K was studied. Rearrangement of ClC(O)SCN to ClC(O)NCS
was observed in the neat liquid and under UV–vis irradiation
of ClC(O)SCN isolated in solid argon. Properties have been discussed
in terms of the valence electronic structure, including the analysis
of the He(I) photoelectron spectrum of ClC(O)SCN.