Structure, conformational properties and matrix photochemistry of S-(tert-butyl)trifluorothioacetate CF3C(O)SC(CH3)3

Abstract

S-(tert-Butyl)trifluorothioacetate, CF₃C(O)SC(CH₃)₃, was prepared by condensation of CF₃C(O)Cl and (CH₃)₃CSH under vacuum conditions. The compound was isolated and properly characterized by using vibrational (infrared and Raman), UV-Vis and multinuclear NMR spectroscopy techniques and by mass spectrometry. The conformational preference and its crystal structure have been determined by means of FTIR spectroscopy (gas phase and Ar-matrix) and by X-ray diffraction. A charge density determination of X-ray diffraction (XRD) data of single crystals formed by in situ crystallization reveals the presence of solely a synperiplanar conformation (syn form orientation of the CO double bond with respect to the S–C single bond) belonging to the C_s point group of symmetry. Intermolecular CO⋯CO and CO⋯H–C interactions were detected in the crystal. Quantum-chemical calculations at the B3LYP/cc-pVTZ level of approximation reproduce the conformational preference and the experimental geometrical parameters fairly well. Vibrational information was obtained from Ar-matrix isolation FTIR and liquid Raman spectroscopy. Additionally, CF₃C(O)SC(CH₃)₃ isolated in solid Ar at ca. 15 K was irradiated with UV-visible broadband light (200 ≤ λ ≤ 800 nm) and its photolysis products CF₃SC(CH₃)₃ and CO were detected.