Thermochemical stabilities and structures of the gas-phase cluster ions of halide ions with OCS

Gas-phase clustering reactions of halide ions with carbonyl sulfide were studied using a pulsed electron-beam mass spectrometer. For F−, formation of a stable FCSO− species was found with the F−–CSO binding energy of >30 kcal/mol (the calculated value=33.41 kcal/mol). DFT calculations showed that the three-fold in-plane coordination to the n=1 species is stable. For Cl−, Br− and I−, the bond energies of cluster ions are in the range of 5–10 kcal/mol with symmetric geometries. All cluster geometries except for F− with n=1 are controlled by the σ∗ vacant orbital of OCS with participation of the sulfur 3dz2−(x2+y2) atomic orbital.