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of MCCs containing interstitial main group atoms.[4-10] Carbide MCCs are known for several
transition metals, but Nickel is the element which displays the largest variety of carbide
clusters.[16-21]
Nickel carbonyl clusters containing one, two, four, six and eight isolated carbide atoms are
known.[17-19] These are usually enclosed within trigonal prismatic (TP), mono-capped trigonal
prismatic (cTP) and square anti-prismatic (SA) cavities, whereas (highly distorted) octahedral (Oh)
cages are rarer. This is due to the fact that carbon is too large in order to fit in a regular octahedral
Ni6C-cage. As a result, Ni carbonyl poly-carbide clusters usually display rather complex and
irregular structures, compared to homometallic MCCs and carbides of larger transition
metals.[22,23]
In addition, Nickel carbonyl clusters containing one, two and four tightly bonded C–C
(acetylide) units have been described.[20,21] Recently, we have reported the
[Ni12(C)(C2)(CO)17(AuPPh3)3]– cluster, which is the first molecular MCC containing at the same
time one carbide atom and one tightly bonded C2-unit. These display sub-van der Waals contacts,
suggesting the incipient formation of more extended C-C bonding within the metal cage of
MCCs.[24] At this regard, the study of molecular carbide clusters can help to a better understanding
of the interaction between metal cages and carbide atoms or C2-units. It must be remarked that
metal surfaces, metal crystallites and metal nanoparticles are active catalysts in several chemical
reactions as well as for the preparation of carbon nanotubes and other nanostructured carbon-based
materials.[25-28]
Generally speaking, carbide MCCs are interesting both at the molecular level and as
precursors for the preparation of metal nanoparticles with controlled composition.[11,29,30] At the
molecular level, carbide MCCs often display rather different properties than analogous
homometallic species, and can more easily reach higher nuclearities.[7a,11,12b,13,31] In addition,
high nuclearity molecular MCCs containing a few tenths or more of metal atoms and possessing
diameters of ca. 1-3 nm can be viewed as atomically defined ultra-small metal nanoparticles.[11]
Thus, their study may contribute to a better understanding of the chemical, structural and physical
properties of metal nanoparticles. Therefore, it would be helpful to obtain larger molecular clusters
containing a higher number of carbide atoms and/or acetylide units, in order to get a better insight
into their structures and organization of the C-atoms.
Herein, we report the synthesis and structural characterization of the first Ni deca-carbide
carbonyl cluster, i.e., [Ni45C10(CO)46]6–. This has been obtained in good yields from the reaction of
[Ni10(C)2(CO)16]2– with CuCl. As a side product, the bimetallic Ni-Cu octa-carbide
[HNi42C8(CO)44(CuCl)]7– has been isolated. This species is isostructural to the previously reported
2