Dimers of Perhaloacetyl Cyanides: CClF₂C(O)OC(CN)₂CClF₂ and CF₃C(O)OC(CN) ₂CF₃. Preparation, Properties, and Spectroscopy

Abstract

The vapor of the new compound 1,1-dicyano-2-chloro-2,2-difluoroethyl chlorodifluoroacetate, CClF2C(O)OC(CN)2CClF2 and of the known 1,1-dicyano-2,2,2-trifluoroethyl trifluoroacetate, CF3C(O)OC(CN)2CF3, were investigated using vibrational spectroscopy tools. The existence of rotational isomerism was confirmed for CClF2C(O)OC(CN)2CClF2 when the matrix isolated compound was examined in combination with the computational results applying quantum chemical models. From the four conformers gauche-syn-gauche, gauche-syn-anti, syn-syn-anti, syn-syn-gauche (the used nomenclature is with respect to the ϕ(ClC-C(O)), ϕ((O)C-OC), and ϕ(OC-CCl) torsion angles, respectively) predicted for CClF2C(O)OC(CN)2CClF2 the first two forms can be evidenced using Ar-matrix IR spectroscopy, with the first one being the most abundant at room temperature. On the other side, the results obtained for CF3C(O)OC(CN)2CF3 reveals the existence of only one syn-syn-anti form. CClF2C(O)OC(CN)2CClF2 melts at -40 °C and its vapor pressure was fitted by the equation ln p = -4732.6 (1/T) + 10.75 (p [Atm], T [K]) in the range -20 to 20 °C. Its extrapolated boiling point is 167 °C. The first ionization potentials occur for CClF2C(O)OC(CN)2CClF2 and CF3C(O)OC(CN)2CF3 at 12.13 and 12.43 eV, respectively, and were attributed to the ejection of electrons formally located at the carbonylic oxygen lone-pair electrons (nO). The proposed interpretation of the photoelectron spectrum is consistent with related molecules reported previously, and also with the prediction of Outer Valence Green's Functions (OVGF).