title: Chlorodifluoroacetyl isothiocyanate, ClF2CC(O)NCS: preparation and structural and spectroscopic studies.
abstract: Chlorodifluoroacetyl isothiocyanate, ClF2CC(O)NCS, was synthesized by the reaction of ClF2CC(O)Cl with an excess of AgNCS. The colorless product melts at -85 °C, and its vapor pressure follows the equation ln p = -4471.1 (1/T) + 11.35 (p [atm], T [K]) in the range -38 to 22 °C. The compound has been characterized by IR (gas phase, Ar matrix, and matrix photochemistry), by liquid Raman, by (19)F and (13)C NMR, gas UV-vis, and photoelectron spectroscopy (PES), by photoionization mass spectrometry (PIMS), and by gas electron diffraction (GED). The conformational properties of ClF2CC(O)NCS have been analyzed by joint application of vibrational spectroscopy, GED and quantum chemical calculations. The existence of two conformers has been detected in the gas and liquid phases, in which the C-Cl bond adopts a gauche orientation with respect to the C═O group; the C═O group is in syn- or anti-position with respect to the N═C double bond of the NCS group. The computed ΔG° difference between these two gauche-syn and gauche-anti forms is ΔG° = 0.63 kcal mol(-1) in the B3LYP/6-31G(d) approximation. The most significant gas-phase structural parameters for gauche-syn ClF2CC(O)NCS are re(NC═S) 1.559(2) Å, re(N═CS) 1.213(2) Å, re(N-C) 1.399(7) Å, re(C═O) 1.199(2) Å, and ∠e(CNC) 134.7(13)°. Photolysis of ClF2CC(O)NCS using an ArF excimer laser (193 nm) mainly yields ClF2CNCS, CO, and ClC(O)CF2NCS. The valence electronic properties of the title compound were studied using PES and PIMS. The experimental first vertical ionization energy of 10.43 eV corresponds to the ejection primarily of the sulfur lone-pair electrons of the in-plane nonbonding orbital on the NCS group.
authors.affiliation: CEQUINOR (UNLP-CONICET, CCT-La Plata), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 esq. 115, 1900 La Plata, República Argentina.
authors.forename: Luis A
authors.initials: LA
authors.lastname: Ramos
authors.forename: Sonia E
authors.initials: SE
authors.lastname: Ulic
authors.forename: Rosana M
authors.initials: RM
authors.lastname: Romano
authors.forename: Yury V
authors.initials: YV
authors.lastname: Vishnevskiy
authors.forename: Norbert W
authors.initials: NW
authors.lastname: Mitzel
authors.forename: Helmut
authors.initials: H
authors.lastname: Beckers
authors.forename: Helge
authors.initials: H
authors.lastname: Willner
authors.forename: Shengrui
authors.initials: S
authors.lastname: Tong
authors.forename: Maofa
authors.initials: M
authors.lastname: Ge
authors.forename: Carlos O
authors.initials: CO
authors.lastname: Della Védova
mesh_terms: D006846:Hydrocarbons, Halogenated / Q000737:chemistry*; D017879:Isothiocyanates / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D011789:Quantum Theory; D012834:Silver / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D013861:Thiocyanates / Q000737:chemistry*
chemical_list: D006846:Hydrocarbons, Halogenated; D017879:Isothiocyanates; D013861:Thiocyanates; D012834:Silver