Abstract
Copper–hydrides
are known catalysts for several technologically important reactions
such as hydrogenation of CO, hydroamination of alkenes and alkynes,
and chemoselective hydrogenation of unsaturated ketones to unsaturated
alcohols. Stabilizing copper-based particles by ligand chemistry to
nanometer scale is an appealing route to make active catalysts with
optimized material economy; however, it has been long believed that
the ligand–metal interface, particularly if sulfur-containing
thiols are used as stabilizing agent, may poison the catalyst. We
report here a discovery of an ambient-stable thiolate-protected copper–hydride
nanocluster [Cu
25
H
10
(SPhCl
2
)
18
]
3–
that readily catalyzes hydrogenation
of ketones to alcohols in mild conditions. A full experimental and
theoretical characterization of its atomic and electronic structure
shows that the 10 hydrides are instrumental for the stability of the
nanocluster and are in an active role being continuously consumed
and replenished in the hydrogenation reaction. Density functional
theory computations suggest, backed up by the experimental evidence,
that the hydrogenation takes place only around a single site of the
10 hydride locations, rendering the [Cu
25
H
10
(SPhCl
2
)
18
]
3–
one of the
first nanocatalysts whose structure and catalytic functions are characterized
fully to atomic precision. Understanding of a working catalyst at
the atomistic level helps to optimize its properties and provides
fundamental insights into the controversial issue of how a stable,
ligand-passivated, metal-containing nanocluster can be at the same
time an active catalyst.