Mechanistic Aspects of the Holmium-Mediated, Reciprocal Hydrogen/Sulfur Exchange in the Gas Phase: C6 H5 CH3 +CH2 S→C6 H5 CHS+CH4.

The thermal reaction of Ho(CH2S) with toluene giving rise to C6H5CHSHo and CH4 has been investigated using Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry complemented by density functional theory (DFT) calculations. The high reactivity of Ho(CH2S) which is in distinct contrast with the non-reactivity of "bare" Ho(+) has its origin in the presence of a carbon-centered radical; the latter initiates hydrogen-atom abstraction from the methyl group of toluene as the first step of a sequence of hydrogen and sulfur transfer mediated by cationic holmium.