The Structure of CCl5- 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 C3v 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.