Guided Ion Beam Tandem Mass Spectrometry and Theoretical Study of SO₂ Activated by Os

The kinetic-energy dependence of SO₂ activated by Os⁺ was studied by guided ion beam tandem mass spectrometry. Species observed in endothermic reactions were OsO⁺, OsO₂⁺ or OsS⁺, and OOsS⁺. The kinetic energy-dependent cross sections were modeled to yield 0 K bond dissociation energies (BDEs) of 5.01 ± 0.06 eV (Os⁺-O), 5.15 ± 0.07 eV (Os⁺-O₂), 4.50 ± 0.17 eV (Os⁺-S), and 4.22 ± 0.11 eV (Os⁺-SO). Among these BDE values, the values for OsO⁺ and OsO₂⁺ agree with literature values and those for OsS⁺ and OOsS⁺ are novel measurements. Theoretical calculations were performed at a B3LYP/def2-TZVPPD level for all products, and additional calculations were performed for OsS⁺, OsO₂⁺, and OsSO⁺ using the CCSD(T) level of theory, extrapolated to the complete basis set (CBS) limit, and def2-QZVPPD and aug-cc-pVxZ (x = T, Q, and 5) basis sets. These calculations indicate that the ground states of the products are ⁴Π_5/2 (OsO⁺), ²B₁ (OsO₂⁺), ⁴Π_5/2 (OsS⁺), and ²A″ (OOsS⁺) after including empirical spin-orbit corrections. The potential energy surfaces (PESs) for OsSO₂⁺ intermediates, transition states, and all products were also investigated at the B3LYP/def2-TZVPPD level. The PESs show that none of the reactions have barriers in excess of the product endothermicities. Cross sections for OsO⁺ formation are compared to those from previous guided ion beam studies of related systems (Os⁺ + O₂ and CO and Re⁺ + SO₂) to evaluate their relative behaviors.