In conclusion, we have prepared a triniobium aqua ion
containing a perpendicularly coordinated μ3-nitrile ligand
which acts as 4e donor. Thismode of coordination has so far
only been reported for (Cp*Ru)3(μ3-η2:η2(^)-RCN)(μ3-H)-
(μ-H)2 where the highly electron-rich ruthenium centers
coupled with the electron-releasing Cp* groups has been
thought to be responsible for enabling such unusual coordination
of a nitrile ligand. Here, we have a formally electron
deficient triniobium center. Substantial electron delocalization
from μ2-O’s as well as eitherH2OorNCS- ligands could
be expected to contribute toward stabilization of unusual 4enitrile
coordination. Last but not least, the [Nb3 (μ-η 2:η2-
NCCH3)O3(H2O)9]6þ
aqua ion is the first organometallic
cluster aqua ion to be reported and is the only example of an
organometallic specieswith several peripheral ligands around
each metal which are all completely water ligands