Observation of Elusive CF2Cl…Cl in Matrix Infrared Spectra and Density Functional Calculations

$CF_2Cl{\cdots}Cl$, an elusive photo-isomer of $CF_2Cl_2$, has been observed in matrix IR spectra from the precursors exposed to radiation from laser ablation of transition-metals. Other plausible products, $CFCl_2{\cdots}F$ and $FClC{\cdots}F-Cl$ are not detected due to their considerably higher energies. Parallel to its previously reported analogues, the C-X bonds are considerably stronger than those of the reactant, and particularly the Cl atom that is weakly bound to the residual Cl atom forms an unusually strong carbon-halogen bond. NBO analysis reveals that the C-Cl bond is a true double bond, and the weak $Cl{\cdots}Cl$ bond is largely ionic, $F_2C=Cl^{\delta+}{\cdots}Cl^{\delta-}$. IRC computation reproduces smooth inter-conversion between the reactant and product, and the transition state is energetically close to the product, consistent with its prompt disappearance in the early stage of photolysis.