Matrix-Isolation Study of the Reaction of F Atoms with CO. Infrared and Ultraviolet Spectra of the Free Radical FCO

Abstract

FCO has been obtained in a CO and in an Ar matrix at 4°, 14°, and 20°K by the reaction with CO of F atoms produced upon photolysis of OF₂, of NF₂, or of t‐N₂F₂, as well as by the photolysis of F₂CO or of HFCO. The three vibrational fundamentals of the free radical FCO appear at 1855, 1018, and 626 cm⁻¹. Experiments employing ¹³C¹⁶O and ¹²C¹⁸O confirm the infrared identification of FCO. In ultraviolet‐absorption studies on matrix‐isolated FCO an extensive series of bands has been observed between 2200 and 3400 Å. The most prominent progression in this system involves bands spaced at approximately 650‐cm⁻¹ intervals. It is likely that this progression is associated with the upper‐state bending mode of FCO. F₂CO and (FCO)₂ are also produced in the reaction of F atoms with a CO matrix, and features of their infrared spectra are reported. A supplementary observation of the ultraviolet‐absorption spectrum of gaseous F₂CO shows a band system between 1800 and 2100 Å, with spacings of approximately 1700 cm⁻¹. Presumably this system is contributed by the n→π^* carbonyl transition. The approximate geometric structure and the nature of the chemical bonds of FCO are discussed, and the mechanisms of formation of this species and of the other observed products are considered. An estimate of the thermodynamic properties of FCO is given.