Chemistry Reference
In-Depth Information
Scheme 2 Syntheses of Au
9
and Au
11
clusters by the reduction with zero-valent titanium reagent
Scheme 3 Examples of PGC syntheses via etching reactions
3.1 Direct Syntheses from Gold Complex Ion or Bulk Gold
3.1.1 Borohydride or Borane Reduction of Gold(I) Phosphine Complex
The borohydride reduction of monophosphine gold(I) complex (Au(PR
3
)X) in
ethanol is the original recipe and has been most widely used as a conventional
method, which generally yields Au
9
[
27
,
37
,
38
,
61
,
62
]orAu
11
species [
19
,
44
-
48
,
63
-
65
]. NaBH
4
is commonly exploited as the reducing agent, because of the ease in
handling. From gold(I) triarylphosphine complex (Au(PAr
3
)
3
X) with a strongly
coordinating anion (X
Cl, I, SCN, S-4-py), neutral deca-coordinated undecagold
clusters Au
11
(PAr
3
)
7
X
3
(e.g., 23-27, Table
1
) are preferentially formed
(Scheme
1
a), whereas the formation of cationic octa-coordinated nonagold cluster
[Au
9
(PAr
3
)
8
]
3+
(e.g., 14-16) is preferred when X is NO
3
with a weak coordinating
character (Scheme
1
a). The steric hindrance and the presence of additional coordi-
nation sites in the phosphine ligand affect the extent of the cluster growth processes.
ΒΌ
