The molecular Pt nanocluster [Pt
27
(CO)
31
]
4–
(
1
4–
)
was obtained by thermal decomposition of [Pt
15
(CO)
30
]
2–
in tetrahydrofuran under a H
2
atmosphere. The reaction of
1
4–
with increasing amounts of HBF
4
·
Et
2
O afforded the previously reported [Pt
26
(CO)
32
]
2–
(
3
2–
) and [Pt
26
(CO)
32
]
−
(
3
–
).
The new nanocluster
1
4–
was characterized by IR and UV–visible spectroscopy, single-crystal
X-ray diffraction, direct-current superconducting quantum interference
device magnetometry, cyclic voltammetry, IR spectroelectrochemistry
(IR SEC), and electrochemical impedance spectroscopy. The cluster
displays a cubic-close-packed Pt
27
framework generated
by the overlapping of four ABCA layers, composed of 3, 7, 11, and
6 atoms, respectively, that encapsulates a fully interstitial Pt
4
tetrahedron. One Pt atom is missing within layer 3, and this
defect (vacancy) generates local deformations within layers 2 and
3. These local deformations tend to repair the defect (missing atom)
and increase the number of Pt–Pt bonding contacts, minimizing
the total energy. The cluster
1
4–
is perfectly diamagnetic and displays a rich electrochemical
behavior. Indeed, six different oxidation states have been characterized
by IR SEC, unraveling the series of
1
n
–
(
n
= 3–8)
isostructural nanoclusters. Computational studies have been carried
out to further support the interpretation of the experimental data.