Guided ion beam and theoretical studies of the reactions of Pd+ with CS2: thermochemistry of PdS+ and PdCS+.
The gas-phase reactivity of the atomic palladium cation with CS(2) is investigated using guided-ion beam mass spectrometry. Endothermic reactions forming PdS(+) and PdCS(+) are observed. Analysis of the kinetic energy dependence of the cross sections for formation of the two products yields the 0 K bond energies of D(0)(Pd(+)-S) = 2.36 +/- 0.11 eV and D(0)(Pd(+)-CS) = 2.67 +/- 0.21 eV. Quantum chemical calculations are used to investigate the electronic structure of the two product ions. In addition, detailed calculations of the potential energy surfaces reveal that the mechanism involves oxidative addition of a CS bond to the metal cation followed by simple bond cleavages. Formation of the ground-state PdS(+) ((4)Sigma(-)) product is spin-forbidden from ground-state Pd(+) ((2)D) whereas PdCS(+) ((2)Sigma(+)) formation is spin-allowed. Crossing points between the doublet and quartet surfaces are located in the region of the SPd(+)(CS) intermediate, which suggests that coupling between the surfaces is efficient, consistent with experimental indications.
Department of Chemistry, University of Utah, 314 S. 1400 E. Rm 2020, Salt Lake City, Utah 84112, USA. armentrout@chem.utah.edu
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Armentrout
Ilona
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Kretzschmar