Chemistry Reference
In-Depth Information
Chapter 10
POP-Type MMX-Chain Compounds with
Binary Countercations and Vapochromism
Hiroaki Iguchi, Shinya Takaishi, and Masahiro Yamashita
10.1
Introduction
10.1.1 Chemistry of pop-Type Discrete Diplatinum Complexes
Pyrophosphito-bridged diplatinum complex is one of the most studied dinuclear
complexes in a paddle-wheel structure. The chemistry of pyrophosphito-bridged
diplatinum complex began at
the discovery of
the Pt(II)-Pt(II)
complex,
P
2
H
2
O
5
2
)byRoundh leta .in1977[
1
]. Since
[Pt
2
(pop)
4
]
4
shows intense long-lived phosphorescence, photochemistry and
excited-state chemistry of [Pt
2
(pop)
4
]
4
has been attracted much attention (see follow-
ing early reviews and references therein [
2
,
3
]). Although no chemical bond exist
between two Pt(II) atoms in the ground state, 5d
K
4
[Pt
2
(pop)
4
]
2H
2
O(pop
¼
transition should induce
the bonding character between them. This excited-state structure has been confirmed by
several optical methods [
4
-
9
]. The excited state of [Pt
2
(pop)
4
]
4
is powerful one-
electron reductant, therefore, it can be used as a photochemical catalyst for converting
ethanol to acetaldehyde and hydrogen [
10
] and for the transfer hydrogenation of
alkenes and alkynes [
11
,
12
]. The Pt(III)-Pt(III) complex, [Pt
2
(pop)
4
H
2
]
4
, is the active
species of the catalytic reaction [
13
].
Although [Pt
2
(pop)
4
H
2
]
4
is unstable species, many stable Pt(III)-Pt(III)
complexes, [Pt
2
(pop)
4
X
2
]
4
(X
s
*
!
6p
s
Cl, Br, I, NO
2
, SCN, etc.) and [Pt
2
(pop)
4
L
2
]
2
¼
(L
H
2
O, py, CH
3
CN, etc.), have been synthesized by the oxidative additions,
occasionally in the presence of the chemical oxidants (see following early reviews
and references therein [
2
,
3
]). Some Pt(III)-Pt(III) complexes exhibit unique strong
red luminescence [
14
].
¼
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