The Structure of CCl 5^- In the Gas Phase

The first experimental evidence of the structure of the CCl5^- gas-phase anion complex is presented in conjunction with results from high-level theoretical calculations. The photoelectron spectrum of the system shows a single peak with a maximum at 4.22 eV. Coupled cluster single double (triple) detachment energies of two stable C_3v ion-molecule complexes of the form Cl^-···CCl₄ were also determined. The first complex found features the Cl^- bound linearly in a Cl^-···Cl-C bonding arrangement, while the second, less stable minimum has the Cl^- positioned at the face of the CCl₄ molecule, midway between three chlorine atoms. The calculated detachment energy for the first complex was found to be in excellent agreement with experiment, allowing the structure of CCl5^- in the gas phase to be postulated as a noncovalent Cl^-···CCl₄ anion complex, with the Cl^- anion tethered by a typical halogen bond.