Chemistry Reference
In-Depth Information
Fig. 32 Ionic products formed after the reaction of Au
3
+
(
a
,
d
,
g
), Ag
2
Au
+
(
b
,
e
,
h
) and Ag
3
+
(
c
,
f
,
i
) with CO (
a
-
c
) and H
2
O(
d
-
f
)at300K(
p
(He) ¼ 1 Pa;
p
(CO) ¼ 0.02 Pa, except in (
b
)
p
(CO) ¼ 0.22 Pa;
p
(H
2
O) ¼ 0.003 Pa). The spectra in the right column display product ion mass
distributions obtained when both reactive molecules CO and H
2
O were present in the ion trap (
p
(CO)
¼
0.04 Pa,
p
(H
2
O)
¼
0.004, 300 K) for Au
3
+
(
g
), Ag
2
Au
+
(
h
) and Ag
3
+
i
). All the spectra
were obtained after a reaction time of 500 ms. Figure reproduced from [
320
]
ð
þ
þ
Þ
þ
Ag
2
Au CO
H
2
O
!
Ag
2
Au CO
ðÞ
ð
H
2
O
ð
69
Þ
Þ
þ
þ
Þ
2
Ag
2
Au CO
ðÞ
ð
H
2
O
H
2
O
!
Ag
2
Au CO
ðÞ
ð
H
2
O
ð
70
Þ
4.4 Catalysis by Gold Cluster Ions
Trapping mass spectrometers are uniquely suited to study complete catalytic cycles
[
44
]. In 1981, Kappes and Staley reported groundbreaking research on the first
examples of transition-metal-catalysed reactions in the gas phase using an ICR
mass spectrometer [
321
]. A key reaction they studied was the oxidation of CO
(Eq. (
71
)), which is exothermic (
107 kcal mol
1
) but does not occur at
room temperature in the absence of a catalyst. They described a simple two-step
catalytic cycle for the oxidation of CO catalysed by the atomic iron cation
ʔ
H
¼
