Molybdenum sulfides are considered a promising and inexpensive
alternative to platinum as a catalyst for the hydrogen evolution reaction.
In this study, we perform collision-induced dissociation experiments
in the gas phase with the halogenated molybdenum sulfides [Mo3S7Cl6]2–, [Mo3S7Br6]2–, and [Mo3S7I6]2–. We show that
the first fragmentation step for all three dianions is charge separation
via loss of a halide ion. As a second step, further halogen loss competes
with the dissociation of a disulfur molecule, whereas the former becomes
energetically more favorable and the latter becomes less favorable
from chlorine via bromine to iodine. We show that the leaving S2 group is composed of sulfur atoms from two bridging groups.
These decomposition pathways differ drastically from the pure [Mo3S13]2– clusters. The obtained
insight into preferred dissociation pathways of molybdenum sulfides
illustrate possible reaction pathways during the activation of these
substances in a catalytic environment.