Chemistry Reference
In-Depth Information
Fig. 22 Examples of gold organothiolato-and cadmium bromide staple ligands [
97
,
98
]
and [Au
2
(SR)
3
] have been given the portmanteau description “staple motifs”, in
order to emphasise their important role in protecting and stabilising the central gold
core, by forming bridging bidentate ligands, with the appropriate bite angles. These
two examples are the first three members of the series of [Au
x
(SR)
x
+1
] ligands
(
m
¼ 0, 1, 2, 3, etc.), which have been studied theoretically and may be observed in
future structure determinations. Related cyclic organothiolato-ligands,
e.g. [Au
4
(SR)
4
], also shown in Fig.
22
, have also been proposed as potential ligating
systems and studied extensively by DFT molecular orbital calculations by
H¨kkinen and co-workers [
97
,
99
-
105
]. These calculations have provided interest-
ing insights into the bonding capabilities of these ligands and higher oligomers of
[Au
x
(SR)
x
+1
] as well as neutral cyclic [Au
x
(SR)
x
] ligands. The strength of the gold-
sulphur bond in organometallic clusters and the bonding preferences of “staple”
ligands have been addressed by H¨kkinen and concluded that the M-SR bond is
strong and comparable to the metal-metal bond, i.e. Au-SR has been calculated to
