Spectroscopic Characterization and Constitutional and Rotational Isomerism of ClC(O)SCN and ClC(O)NCS

LUIS 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; SCHENGRUI TONG; CARLOS O. DELLA VÉDOVA

JOURNAL OF PHYSICAL CHEMISTRY A

AMER CHEMICAL SOC

Lugar: Washington; Año: 2013 vol. 117 p. 2383 - 2399

1089-5639

Chlorocarbonylthio- and isothiocyanate (ClC(O)SCN and ClC(O)-NCS) have been isolated and characterized by IR (Ar matrix, gas), Raman (liquid), 13CNMR and UV−visible spectroscopies. Vibrational and quantum chemical studies suggestthe presence of the syn and anti conformers (SCN group with respect to the CObond) in the gas phase for both constitutional isomers. syn-ClC(O)SCN is preferred byΔH° (anti/syn) = 1.3(0.3) kcal mol−1. The solid-state structure of ClC(O)SCN hasbeen determined by single crystal X-ray diffraction analysis at low temperature. Thecrystalline solid consists exclusively of molecules in the syn conformation. On the otherhand, the anti form is more stable for the ClC(O)NCS isomer. The structure ofClC(O)NCS and its conformational composition were determined by gas electrondiffraction. An unusual low syn → anti interconversion energy barrier of 0.98 (0.15) kcalmol−1 was detected for ClC(O)NCS at cryogenic temperatures. The photochemistry ofboth constitutional isomers isolated in solid argon at 15 K was studied. Rearrangementof ClC(O)SCN to ClC(O)NCS was observed in the neat liquid and under UV−visirradiation 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.