Dehydrohalogenation versus dehydrogenation in reaction of Au+ with CH3Cl: A theoretical study

The reaction of Au+ (1S, 3D) with CH3Cl has been investigated at B3LYP and CCSD(T) levels of theory. The reaction pathways of both HCl- and H2-elimination were identified on the singlet surface, whereas only H2-elimination pathway was found on the triplet surface. The calculated results indicate that HCl-elimination is energetically much more favorable than H2-elimination. Two reaction pathways were identified for HCl-elimination: (a) Au++CH3Cl → Cl-Au+-CH3 → ClAuH+-CH2 → (HCl)-Au+-CH2 → HCl+AuCH2+; (b) Au++CH3Cl→H-Au+-CH2Cl → Au+-CH2(HCl) → HCl+AuCH2+. Pathway a has activation energy barrier of 25.2 kJ/mol at CCSD(T) level, while pathway b is barrierless. In addition, formation of other possible products (AuCl+, AuCl, AuH+ and AuH) has also been discussed. All the results of this study well rationalized the experimental observations.