Chemistry Reference
In-Depth Information
Fig. 27 Molecular orbital
for triangular Au
6
molecular orbitals with the stoichiometries [Au
30
{(SR)
22
] based on [Au(SR)
2
] and
[Au
41
(SR)
33
] based on [Au
2
(SR)
3
] staple motifs. Of course intermediate combina-
tions of these ligands may also be present in the isolated cluster.
3.7.2 Cuboctahedral-Based Structures
The previous section suggested that a centred cuboctahedron of gold atoms has similar
bonding characteristics to the icosahedron because they are both essentially spherical.
The centred Au
13
cuboctahedron could also form the basis of a similar series of
conjoined clusters - starting with [Au
25
(SR)
18
] which is predicted to have a centred
cuboctahedron inside a staple ligand shell based on 6[Au
2
(SR)
3
]. [Au
38
(SR)
24
]would
be based on a pair of cuboctahedra sharing a triangular face. Finally a pair of fused
cuboctahedra has 20 surface atoms and the skeletal bonding requirement of [S
σ
]
2
[P
σ
]
6
suggests the following homoleptic relationships:
Au
20
Au S
ð
2
12
:
12
þ
½
Au
20
L
24
Au
20
S
ð
12
12
Au
32
S
ð
24
Au
20
Au
2
S
ð
3
12
Au
44
S
ð
36
:
Au
20
Au S
ð
2
The single crystal structure determination of [Au
28
(SR)
20
] has confirmed that it
has a fused bi-cuboctahedral core with 8 bridging SR and 4 [Au
2
(SR)
3
] staples and
corresponds to the following intermediate substitution:
