Conformational and structural determination of F2NC(O)F and F2NC(O)NCO: A joint experimental and theoretical study

Abstract

The vibrational properties of two difluoroaminocarbonyl species were analyzed by recording the FTIR spectra of the vapor for difluoroaminocarbonyl fluoride, F2NC(O)F, and difluoroaminocarbonyl isocyanate, F2NC(O)NCO. Moreover, the Raman spectrum of liquid F2NC(O)NCO was obtained. Vibrational assignments were made on the basis of a normal coordinate analysis and the evaluation of the band contours appearing in the FTIR spectrum of the vapor. The conformational space of both difluoroaminocarbonyl derivatives were studied by using the B3LYP and MP2 level of theory with extended basis sets [6-311+G(3df) and aug-ccpVTZ]. Only one conformation belonging to the C1 symmetry point group is expected for F2NC(O)F, whereas the overall evaluation of experimental and theoretical results suggests the existence of a mixture of two conformers for F2NC(O)NCO at room temperature. Its relative abundance of the most stable syn form (CdO double bond syn with respect to the NdCdO group) was estimated to be 56(5) %.