Chlorodifluoroacetyl Isocyanate, ClF₂CC(O)NCO: Preparation and Structural and Spectroscopic Studies

Abstract

Chlorodifluoroacetyl isocyanate, ClF2CC(O)NCO, was prepared by the reaction of ClF2CC(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 ClF2CC(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 ΔH(exp)° = 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 ClF2CC(O)NCO are r(e)(NC═O) = 1.157(1) Å, r(e)(N═CO) = 1.218(1) Å, r(e)(N–C) = 1.378(9) Å, r(e)(C═O) = 1.195(1) Å, angle(e)(CNC) = 128.6(19)°. Photolysis of ClF2CC(O)NCO using an ArF excimer laser (193 nm) mainly yield ClF2CNCO along with some ClF2CC(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.

Carbonyl Diisocyanate CO(NCO)2: Synthesis and Structures in Solid State and Gas Phase

“…The structural parameters obtained for the two conformers of CO­(NCO) 2 can be compared to the structural parameters of previously examined compounds, FC­(O)­NCO, ClC­(O)­NCO, CH 3 C­(O)­NCO and F 2 ClCC­(O)­NCO . A detailed listing of selected parameters is presented in Table .…”

“…This effect is also observed for ClC(O)NCO 45 where the C−Cl bond is longer in the anti conformer (1.757(5) Å) compared to that of the syn conformer (1.729(5) Å). Furthermore, this effect is observed in F 2 ClCC-(O)NCO 46 for which the gauche−syn conformer has a CC bond of 1.541 (7) Å in length, that is, 0.007 (7) Å shorter than in the gauche−anti conformer. Another difference regarding the geometrical parameters occurs in the isocyanate ∠(NCO) angle.…”

Insights into the Luminescence Thermochromism of a Triarylboron Derivative: The Role of Intramolecular Group Interaction

“…The GS energies indicate that C1 is the most stable one. C2 shows a small energy difference with respect to C1 and contributes significantly to the abundance according to the Boltzmann distribution . C3 is predicted to be less stable than C2 at all levels of theory.…”

“…C2 shows a small energy difference with respect to C1 and contributes significantly to the abundance according to the Boltzmann distribution. 43 C3 is predicted to be less stable than C2 at all levels of theory. Its abundances are less than 7% at 300 K and 3% at 180 K, which might be ignored in reality.…”

Conformation and Structure of Dichlorophosphoryl Isocyanate in the Gaseous and Solid Phases

“…Chemically, isocyanates are not only reactive towards alcohols and amines but also unstable due to self‐additions and trans‐condensations. This is particularly the case for simple α‐oxo‐isocyanates such as acyl isocyanates [RC(O)–NCO], sulfinyl isocyanates [RS(O)–NCO], and sulfonyl isocyanates [RS(O) 2 –NCO], most of which undergo facile oligomerization or polymerization reactions in the condensed phase at room temperature. Therefore, the fundamentally important conformational and structural properties of these compounds remained attracting theoretical and experimental interest in the recent few decades.…”