Chemistry Reference
In-Depth Information
2+
+
2+
N
N
N
N
Coulomb
O
OH
+
Au
Au
Au
Au
Explosion
O
N
N
N
N
O
Scheme 3 Coloumb explosion pathway for dinuclear gold(III) oxo cluster coordinated by
6-substituted 2,2
0
-bipyridyl ligands
MeO
PPh
3
Au
MeO
- (Ph
3
P)
2
Au
Au
PPh
3
1
MeO
MeO
Au
3
MeO
PPh
3
- (Ph
3
P)Ag
Au
MeO
Ag
2
Scheme 4 Gas-phase fragmentation of homo (1) and hetero (2) dinuclear acetylides [
315
]
In contrast, all complexes with alkyl substituents in the 6-position of the ligands
undergo Coulomb explosion to produce two monocationic fragments, as illustrated for
the methyl derivative in Scheme
3
. The difference in behaviour was rationalised by the
combined effects of steric strain introduced to the central Au
2
O
2
core by the substituents
on the bipyridine ligand and the presence of oxidisable C-H bonds in the substituents.
4.2.4 Gem-Diaurated Cluster Ions
There has been considerable interest in the possibility of cooperation of two gold
centres in catalytic reaction pathways, which has been termed 'dual gold catalysis'
[
314
]. A key question is whether the two gold centres are remote from each other or
whether they directly interact via aurophilic interactions. Two studies have
appeared in which mass spectrometry experiments and DFT calculations have
been carried out to locate the site(s) of the Au atoms. In the first, Simonneau
et al. demonstrated that gold acetylides formed the homo (1), and hetero (2)
dinuclear systems, in Scheme
4
under ESI-MS conditions and when subjected to
CID, these fragmented via loss of either (Ph
3
P)
2
Au
+
or (Ph
3
P)Ag
+
[
315
]. On the
