Chemistry Reference
In-Depth Information
Fig. 15 Skeletal molecular orbitals for edge-linked tetrahedra
have reported the structures of several gold-silver clusters [
59
], and the electronic
characteristics of these clusters have been analysed using the molecular orbital
ideas developed above [
84
]. The parent icosahedron exemplified by
[Au
13
X
m
(PMe
2
Ph)
12
m
]
x
+
(
m
¼ 2-4;
x
¼ 5
m
) has a pec of 162 electrons and
a sec associated with 8 electrons occupying [S
σ
]
2
[P
σ
]
6
. For vertex sharing icosahe-
dra which adopt a linear arrangement, the skeletal molecular orbitals are simple
combinations of the skeletal molecular orbitals of the parent icosahedra. Further-
more, vertex sharing does not lead to strong inter-icosahedral interactions, because
the overlap integrals are small [
84
]. Consequently these aggregates of
n
icosahedra
are characterised by [1S
σ
][1P
σ
]
6
,
[2S
σ
][2P
σ
]
6
[nS
σ
]
2
[nP
σ
]
6
,
occupied
......
