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Dimers of perhaloacetyl cyanides: CClF2C(O)OC(CN) 2CClF2 and CF3C(O)OC(CN) 2CF 3. Preparation, properties, and spectroscopy

Abstract:

The vapor of the new compound 1,1-dicyano-2-chloro-2,2-difluoroethyl chlorodifluoroacetate, CClF<inf>2</inf>C(O)OC(CN)<inf>2</inf>CClF<inf>2</inf> and of the known 1,1-dicyano-2,2,2-trifluoroethyl trifluoroacetate, CF <inf>3</inf>C(O)OC(CN)<inf>2</inf>CF<inf>3</inf>, were investigated using vibrational spectroscopy tools. The existence of rotational isomerism was confirmed for CClF<inf>2</inf>C(O)OC(CN)<inf>2</inf>CClF<inf>2</inf> 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 CClF <inf>2</inf>C(O)OC(CN)<inf>2</inf>CClF<inf>2</inf> 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 CF<inf>3</inf>C(O)OC(CN)<inf>2</inf>CF<inf>3</inf> reveals the existence of only one syn-syn-anti form. CClF<inf>2</inf>C(O)OC(CN)<inf>2</inf>CClF<inf>2</inf> 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 CClF <inf>2</inf>C(O)OC(CN)<inf>2</inf>CClF<inf>2</inf> and CF<inf>3</inf>C(O)OC(CN) <inf>2</inf>CF<inf>3</inf> 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 (n<inf>O</inf>). 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). © 2014 American Chemical Society.