C-S Bond Formation Coupled Activation Of Inert C-H Bond Investigated With A Quadrupole-Linear Ion Trap Mass Spectrometer

Cluster is an ideal model for the active sites of condensed-phase catalysts,and the gas-phase reaction of clusters can eliminate the influence of many complicated factors that prevail in condensed-phase reactions.As a result,the combination of gas-phase experiment and quantum-chemical calculation affords rational means to reveal the catalytic mechanism at a strictly molecular level.In this paper,a quadruple-linear ion trap mass spectrometer was designed and built.A laser sputtering-supersonic condensation cluster source was equipped,and the wavelength of the laser light could be adjusted according to the experimental system.It should be noted that more than 90%of components of the mass spectrometer were domestically produced.Moreover,the use of time-of-flight mass analyzer was avoided by adopting the resonance excitation technology,which greatly reduces the space occupied by the instrument and the construction cost.The quadrupole-linear ion trap mass spectrometer was used to study the reaction mechanism of C-H activation through C-S coupling in the S+/CH4 reaction.The single-point energy was obtained at the CCSD(T,full)/aug-cc-pVTZ level of theory with ORCA 4.2.0.Optimization of related structures,frequency analysis and analysis of frontier-orbital of the important stagnation point was completed at the B2GP-PLYP-D3(BJ)/def2-TZVP level of theory with Gaussian 09.It was revealed that the S+cluster reacted with methane quickly when exposed to methane gas to generate[SCH2]+,[SCH3]+and[SCH4]+,of which[SCH3]+was the main product.In addition to S+/CH4,the reaction of S2+/CH4 was also studied.The experimental result showed that S2+cannot activate methane at room temperature.Considering the influence of electron density around S atom on reactivity,the reactivity of S22+to methane was further analyzed theoretically.The calculation result showed that S22+ has a pretty high reactivity in the reaction with methane.In addition to methane activation,the Sn+/C6H6 reaction was also investigated,especially the influences of S-π interaction on the bond breaking and making processes.In order to study the mechanism of C-H activation through S-π bond formation,the reactions of pure sulfur clusters S+,S2+,S3+ with neutral benzene vapor in the gas phase environment were carried out,and the single-point energy was obtained at the B2GP-PLYP-D3(BJ)/Aug-cc-pwCVQZ(AVQZ)level of theory with ORCA 4.2.0.Besides,the related structure optimization and frequency analysis were completed at the B3LYP-D3(BJ)/def2-TZVP level of theory with Gaussian 09.The experimental result showed that S+/C6H6 could generate[C5H6]+,[C6H6]+,[SC4H4]+ and[SC6H6]+,of which the charge transfer product[C6H6]+ was the main product;Only charge transfer occurred in the S2+/C6H6 reaction,generating the sole product[C6H6]+;S3+/C6H6 afforded both the charge transfer product[C6H6]+ and the bond activation product[SC6H6]+.The result of collision-induced dissociation of[SC6H6]+ shows that[SC6H6]+ is structurally characterized by complexation of single S atom with a C6H6 unit.