Theoretical study on the reaction of the 2Δ ground state of ZrO+ with CS2 in the gas phase

The mechanisms for the three products ZrS+, ZrS2+ and ZrOS+ of the title reaction have been studied by using B3LYP/6-311+G∗ and CCSD(T)/SDD+6-311+G∗ methods. It is found that both ZrS+ and ZrS2+ formations involve the same O/S exchange process via a four-center transition state TS12 to form an intermediate IM2. Exception of that IM2 can dissociate into the ZrS+ product, a favorable intramolecular rearrangement mechanism associated with the ZrS2+ formation has been identified, which explains why ZrS+ was excluded as a precusor for the ZrS2+ formation and why the lower efficiency of the ZrS+ formation was observed in experiment. For the formation of ZrOS+, two parallel channels (path A and B) yielding their corresponding product isomer have been identified. Path B involving an insertion-elimination mechanism with a calculated barrier underestimated by ca. 25.0 kJ/mol should be attributed to the threshold of 114.8 ± 12.5 kJ/mol assigned in the experiment. But path A should make some contributions to the formation of ZrOS+ at elevated energy.