Chlorodifluoroacetyl isocyanate, ClF2CC(O)NCO: Preparation and structural and spectroscopic studies

Abstract:

Chlorodifluoroacetyl isocyanate, ClF<inf>2</inf>CC(O)NCO, was prepared by the reaction of ClF<inf>2</inf>CC(O)Cl with excess of AgNCO. The colorless compound melts at -83 °C and the vapor pressure follows the equation ln p = -3868.3 (1/T) + 10.89 (p [Atm], T [K]) in the range -38 to +22 °C, extrapolated bp ca. 82 °C. It has been characterized by IR (gas phase, Ar matrix), liquid Raman, ¹⁹F and ¹³C NMR, gas UV-vis spectrum, photoelectron spectroscopy (PES), photoionization mass spectrometry (PIMS), and gas electron diffraction (GED). The matrix photochemistry has been studied and the conformational properties of ClF<inf>2</inf>CC(O)NCO have been analyzed by joint application of vibrational spectroscopy, GED, and quantum chemical calculations. Two conformers were detected in gaseous and liquid phases, in which the C-Cl bond adopts a gauche orientation with respect to the C=O group, whereas this group can be in syn or anti orientation with respect to the N=C bond of the NCO group. An enthalpy difference δHexp° = 1.3 ± 0.2 kcal mol^-1 between the most stable syn-gauche and the less stable anti-gauche form was derived using the van't Hoff equation, which is in reasonable agreement with the computed difference of δH° = 0.8 kcal mol^-1 (B3LYP/6-311+G(3df) approximation). The most significant gas phase structural parameters for gauche-syn ClF<inf>2</inf>CC(O)NCO are r<inf>e</inf>(NC=O) = 1.157(1) Å, r<inf>e</inf>(N=CO) = 1.218(1) Å, r<inf>e</inf>(N-C) = 1.378(9) Å, r<inf>e</inf>(C=O) = 1.195(1) Å,<inf>e</inf>(CNC) = 128.6(19)°. Photolysis of ClF <inf>2</inf>CC(O)NCO using an ArF excimer laser (193 nm) mainly yield ClF <inf>2</inf>CNCO along with some ClF<inf>2</inf>CC(O)N nitrene. The valence electronic properties of the title compound were studied using the PES and PIMS. The experimental first vertical ionization energy of 11.54 eV corresponds to the ejection of a carbonylic oxygen lone pair electron. © 2012 American Chemical Society.

Año de publicación:

2012

Keywords:

Fuente:

scopus