Gas-phase equilibria for clustering reactions of both halide ions (X-) with methane and chloride ions with chloromethanes (CH4-mClm) were measured with a pulsed electron-beam high-pressure mass spectrometer. The bond energies were found to show irregular decreases for F-(CH4)(n), with n = 6 and 8, for Cl-(CH3Cl)(n), with n = 2, 4, and 6, and for Cl-(CH2Cl2)(n), with n = 2 and 4. These even numbers indicate that the core ions are preferably solvated by the ligands with these n values. The theoretical calculation revealed that the cluster ion Cl-(CCl4) has the structure of [Cl...ClCCl3](-) rather than Cl-...Cl3CCl. The unexpectedly large bond energy for Cl-(CCl4) (13.4 kcal/mol) is due to the charge dispersal in the complex [Cl...ClCCl3](-).