Theoretical study on the reaction of the 2Δ ground state of TiS+ with COS in the gas phase

Two major reactions of the 2Δ ground state of TiS+ with COS in the gas phase have been studied by using density functional theory at B3LYP/DZVP level: the O/S exchange reaction (TiS+ + COS → TiO+ + CS2) and the S-transfer reaction (TiS++COS→TiS2++CO). It is found that the O/S exchange reaction is one-step reaction with an activation barrier of 15.1 kJ/mol relative to the reactants, whereas for the S-transfer reaction, two parallel reaction channels have been identified. From the two cis-trans isomer intermediates (IM3 and IM5) formed Initially from the S atom of COS attacking TiS+, the two reaction channels proceed via a four-center and a three-member transition states with activation barriers of 51.3 and 40.7 kJ/mol, respectively, and yield their corresponding products TiS2+-1(2B2)andTiS2+-2(2A1). Besides, one two-step mechanism of the third major reaction of TiS+ with COS (TiS+ + COS → Ti+ + S2 + CO) has been also identified