Thermochemistry Of The Ir+ + So2 Reaction Using Guided Ion Beam Tandem Mass Spectrometry And Theory

Kinetic energy dependences of the reactions of Ir+ (F-5(5)) with SO2 were studied using a guided ion beam tandem mass spectrometer and theory. The observed cationic products are IrO+, IrS+, and IrSO+, formed in endothermic reactions. Bond dissociation energies (BDEs) of the products are determined by modeling the kinetic energy dependent product cross sections: D-0(Ir+-O) = 4.27 +/- 0.11 eV, D-0(Ir+-S) = 4.03 +/- 0.06 eV, and D-0(Ir+-SO) >= 2.95 +/- 0.06 eV. The oxide BDE agrees well with literature values, whereas the two latter results are novel measurements. Quantum mechanical calculations are performed at the B3LYP level of theory using the def2-TZVPPD basis set for all product BDEs with additional calculations for IrS+, IrO2+, and IrSO+ at the coupled cluster with single, double, and perturbative triple excitation levels with def2-QZVPPD and aug-cc-pVXZ (X = T and Q and for IrS+, also X = 5) basis sets and complete basis set extrapolations. These theoretical BDEs agree reasonably well with the experimental values. (1)A(1) (IrO2+), (5)Delta (4) (IrS+), and (3)A ''/(1)A ' (IrSO+) are found to be the ground states after including empirical spin-orbit corrections. The potential energy surfaces including intermediates and transition states for each reaction are also calculated at the B3LYP/def2-TZVPPD level. The formation of MO+ (M = Re, Os, and Ir) from M+ + SO2 reactions is compared with those from the M+ + O-2 and M+ + CO reactions, where interesting trends in cross sections are observed. Overall, these studies suggest that the M+ + O-2 reactions had restrictions associated with reactions along A ' and A '' surfaces.