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

LUIS A. RAMOS; SONIA E. ULIC; ROSANA M. ROMANO; YURY V. VISHNEVSKIY; RAPHAEL J. F. BERGER; NORBERT W. MITZEL; HELMUT BECKERS; HELGE WILLNER; SHENGRUI TONG; MAOFA GE; CARLOS O. DELLA VÉDOVA

JOURNAL OF PHYSICAL CHEMISTRY A

AMER CHEMICAL SOC

Lugar: Washington; Año: 2012 vol. 116 p. 11586 - 11595

1089-5639

Chlorodifluoroacetyl isocyanate, ClF2CC(O)-NCO, was prepared by the reaction of ClF2CC(O)Cl withexcess of AgNCO. The colorless compound melts at −83 °Cand 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 (gasphase, Ar matrix), liquid Raman, 19F and 13C NMR, gas UV−vis spectrum, photoelectron spectroscopy (PES), photoionizationmass spectrometry (PIMS), and gas electrondiffraction (GED). The matrix photochemistry has beenstudied and the conformational properties of ClF2CC(O)-NCO have been analyzed by joint application of vibrational spectroscopy, GED, and quantum chemical calculations. Twoconformers were detected in gaseous and liquid phases, in which the C−Cl bond adopts a gauche orientation with respect to theCO group, whereas this group can be in syn or anti orientation with respect to the NC bond of the NCO group. Anenthalpy difference ΔHexp ° = 1.3 ± 0.2 kcal mol−1 between the most stable syn−gauche and the less stable anti-gauche form wasderived 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)NCOare re(NCO) = 1.157(1) Å, re(NCO) = 1.218(1) Å, re(N−C) = 1.378(9) Å, re(CO) = 1.195(1) Å, ∠e(CNC) =128.6(19)°. Photolysis of ClF2CC(O)NCO using an ArF excimer laser (193 nm) mainly yield ClF2CNCO along with someClF2CC(O)N nitrene. The valence electronic properties of the title compound were studied using the PES and PIMS. Theexperimental first vertical ionization energy of 11.54 eV corresponds to the ejection of a carbonylic oxygen lone pair electron.