Chemistry Reference
In-Depth Information
Fig. 5 Single-crystal X-ray structures of clusters having a polyhedral core with
exo
-attached gold
atoms. Counter anion: NO
3
(4, 12), PF
6
(11), BF
4
(10), SbF
6
(32)
Table 4 Au-Au bond distances (Å) of butterfly-shaped Au
9
unit of [Au
9
(PPh
3
)
8
]
3+
(14a) and that
of Au
9
+2Au type Au
11
cluster (Au
11
(dppe)
6
)
3+
, 32)
Mean dist. of
Au
9
unit
Radial
Peripheral
exo
-to-core References
[Au
9
(PPh
3
)
8
](NO
3
)
3
(14a·NO
3
)
2.777
2.675-2.708
(2.691)
2.762-2.880
(2.834)
-
[
62
]
[Au
11
(dppe)
6
]
(SbF
6
)
3
(32·SbF
6
)
2.814
2.666-2.824
(2.745)
2.629-2.971
(2.860)
2.777,
2.824
[
74
]
phosphine ligands. The Au
9
core unit is apparently similar to previously known
examples of butterfly-shaped clusters, although it has a slightly wider range of Au-
Au bond distances (2.629-2.971 Å) than [Au
9
(PPh
3
)
8
]
3+
(2.675-2.880 Å) (Table
4
)
[
62
]. Significantly, the
exo
-bridged edges are very short (2.629 Å) compared with
the shortest peripheral-peripheral bonds of the non-
exo
type clusters (i.e., 2.762 Å
for 14a·NO
3
). This may reflect some distortion caused by the bridging of the
exo
gold atoms. The core-to-
exo
distances were 2.777 and 2.824 Å, which lie in the
range of the bond distances in the central butterfly unit.
These core+
exo
type clusters exhibit impressive colors that are different from
conventional centered polyhedral clusters. This aspect will be mentioned in the next
section. Among the three core+
exo
type clusters (Au
6
,Au
8
,Au
11
), Au
8
clusters
(11-13) are different in the context that they have additional anionic ligands
(sub-ligands). The long
exo
-to-core distance in 11-13 can be attributed to the
