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Abstract: The reactions of NbS+ (3∑−, 1Γ) with COS have been studied using density functional theory at the B3LYP level: the O/S exchange reaction (NbS+ +COS→NbO+ +CS2), the S-transfer reaction (NbS+ +COS→ +CO) and the O-transfer reaction (NbS+ +COS→ONbS+ +CS). The different mechanisms on the triplet and singlet surfaces have been identified. It is found that the S-transfer reaction has two parallel reaction paths (path A and path B) with respective to two isomeric products (-1 and -2), which may account, respectively, for the endothermic and the exothermic features of the product cross-section observed in the experiment. The spin-forbidden reaction NbS+ (3∑−)+COS→ (1-A′)+CO was found to be energetically much more favorable than the spin-allowed reaction NbS+ (3∑−)+COS→ (3-A′)+CO. According to the identified reaction mechanisms, a triplet–singlet surface crossing is suggested. The larger activation barriers (23.7 and 59.5kcal/mol) and the small probability of the formation of the preceding intermediate 3IM1 result in a much lower efficiency of the O/S exchange reaction and the O-transfer reaction of the 3∑− ground state of NbS+ with COS. For the O-transfer reaction, a triplet–singlet surface crossing may also exist. [Copyright &y& Elsevier]

Abstract: The reaction mechanism of the Mn+ (7 S and 5 S states) with COS has been studied by means of density functional method (B3LYP). The overall energetics has been refined at the CCSD (T) level. The calculated results indicate that both the C–S and C–O bond activations proceed via an insertion–elimination mechanism. The C–S bond activation is found to be much more favorable than the C–O bond activation. Intersystem crossing between the septuplet and quintet surfaces may occur along both the C–O and C–S bond activation branches. The calculated barriers of spin-forbidden reaction Mn+ (7 S)+COS→MnS+ (5 Π)+CO and spin-allowed reaction Mn+ (7 S)+COS→MnS+ (7 Π)+CO are 17.6 and 43.8kcal/mol, respectively, which are in good agreement with the values assigned in the experiment. [Copyright &y& Elsevier]