FTIR study of the synthesis of anionic platinum carbonyl complexes in faujasites
Abstract
[{Pt
3
(CO)
3
(µ-CO)
3
}
n
]
2-
complexes (Chini complexes)
have been synthesized by the ‘ship-in-bottle’ technique in
X and Y zeolites with different charge-compensating alkali-metal
cations. The reaction kinetics of the reductive carbonylation of the
[Pt(NH
3
)
4
]
2+
complex was examined by
FTIR spectroscopy in order to understand the mechanism of the
formation of the Chini complexes. It was found that three geometrical
arrangements of the [Pt(NH
3
)
4
]
2+
complexes are formed in the cavities and that their occurrence depends
on the zeolite composition (Si/Al ratio, alkali-metal cation) and
amount of water. A decreased content of Al and increasing
electropositivity and radius of the alkali-metal cations accelerate
the decomposition of the [Pt(NH
3
)
4
]
2+
complex during the carbonylation and consequently also the formation
of Chini complexes. A higher content of water reduces the rate of the
carbonylation process but causes the formation of a higher fraction of
smaller Chini complexes.
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