Experimental and Theoretical Studies of the Reaction of Rh+ with CS2 in the Gas Phase: Thermochemistry of RhS+ and RhCS+

Abstract

The gas-phase reactivity of the atomic transition-metal cation rhodium, Rh(+), with CS(2) is investigated using guided-ion-beam mass spectrometry (GIBMS). Endothermic reactions forming RhS(+) and RhCS(+) are observed. Analysis of the kinetic energy dependence of the cross sections for formation of these two products yields the 0 K bond energies of D(0)(Rh(+)-S) = 2.61 +/- 0.12 eV and D(0)(Rh(+)-CS) = 2.66 +/- 0.19 eV. These compare favorably with quantum chemical calculations at the CCSD(T)/Def2TZVPP//B3LYP/Def2TZVPP and CCSD(T)/Def2TZVPP levels of theory, where the former is also used to explore the complete potential energy surface of the reaction. It is found that the reaction initially involves insertion of the rhodium cation into one of the CS bonds of CS(2), followed by metal ligand cleavages to form the two product channels. The formation of ground state RhS(+) products is spin-forbidden, whereas RhCS(+) formation is spin-allowed. Crossing points between the triplet and quintet surfaces are located in the region of the SRh(+)(CS) intermediate, which suggests that coupling between the surfaces is reasonably efficient, consistent with experiment.