Oxidation of Difluorovinylidene

Abstract

Difluorovinylidene is a highly reactive and extremely electrophilic singlet carbene that thermally abstracts an oxygen atom from CO 2 at temperatures as low as 30 K. The resulting difluoroketene is characterized for the first time using IR spectroscopy in combination with isotopic labeling and density functional theory (DFT) calculations. The three observed IR absorptions of the ketene at 1274, 1427, and 2162 cm À1 are assigned to the asymmetrical FCF stretching vibration and the asymmetrical and symmetrical CCO stretching vibrations, respectively. The oxidation of difluorovinylidene with 3 O 2 results in a complex product mixture with CF 2 , C 2 F 4 , CO 2 , COF 2 , and CO as the major products. A mechanism consistent with all observed products is proposed.

Super-electrophilic carbenes and the concept of Philicity

“…The major products are F 2 C: and CO 2 , presumably formed via a ketene O-oxide and a methylenedioxirane as intermediates. 15 However, in contrast to most other carbene oxygenations, these intermediates could not be stabilized in low-temperature matrices.…”

“…This reaction has not been observed with any other carbene. The first step is the electrophilic attack at one of the oxygen atoms, followed by the oxygen atom transfer under formation of F 2 C=O and CO. 15 Both the oxygen atom transfer and the carboxylation are calculated [B3LYP/6-311G(d) ZPE] to be exothermic, but the latter reaction obviously is prevented by a significant activation barrier.…”

Preparation, Spectroscopic Properties, and Crystal Structures of Fe2(CO)6(μ-CO)(μ-CF2)2, Fe2(CO)6(μ-CO)2(μ-CF2), and Fe2(CO)6(μ-CF2)(PPh3)2 - Theoretical Studies of Methylenicvs. Carbonyl Bridges in Diiron Complexes

“…Relative to matrix isolated free CF 2 with the m s (FCF) at 1102 and m as (FCF) at 1221 cm ±1 the two CF vibrations of the complexes 2 to 4 are shifted to lower frequencies [11] and we suppose that in the complexes similarly the bands at higher frequencies can be assigned to the asymmetric CF 2 vibration.…”

Synthesis and chemistry of α-iodoperfluoroacid esters

“…Difluoroketene 13 is well known to Scheme 1. be unstable at RT, decomposing readily into difluorocarbene and carbon monoxide [15]. Derivatives have been prepared [16], and the ketene itself has been observed in matrix isolation [17].…”