Surface organometallic chemistry of rhodium and palladium on titania
Surface organometallic chemistry of rhodium and palladium on titania
The combination of EXAFS and IR results has shown the adsorption of [Rh(CO)2Cl]2 onto titania to result in the formation of a discrete [O]-Rh(CO)2Cl species. Heating of the sample led to the formation of small metal particles at 433 K, with linearly bound CO shown as an intermediate by infrared studies. Further heating led to large, FCC like metal particles. Reaction of [O]-Rh(CO)2Cl with hydrogen will not proceed below 338 K at less than atmospheric pressure. No intermediate carbonyl species were detected for this reaction. Reaction with NO led to the loss of carbonyl coordination, which could be regenerated upon subsequent exposure to CO.
The adsorption of Rh(CO)2(acac), Rh(η3-C3H5)3, [Rh(C2H4)2Cl]2 and Rh(η5-C5H5)(CO)2 has also been investigated. Treatment of Rh(CO)2(acac) / TiO2 with hydrogen, or heating to 473 K leads to the formation of very small metal particles. A RhI(CO)2 species could be regenerated upon exposure to CO after initial reduction by hydrogen. The supported [Rh(C2H4)2Cl]2 species lost its dimeric structure upon reaction with the surface, but was still the least reactive of the rhodium systems, showing only some degree of clustering upon heating to 623 K.
Adsorption of Pd(allyl)cp onto titania results in the loss of allyl coordination. While heating to 573 K or exposure to CO produced large metal particles, reaction with H2 or NO caused only partial reduction of the sample.
A co-supported Rh/Pd system was prepared by simultaneous deposition of [Rh(CO)2Cl]2 and Pd(allyl)cp. This system showed 2 phases upon heating, one of small alloy like particles, the other of larger palladium rich particles, resulting from the Pd:Rh ratio of >1. A system prepared by sequential deposition of [Rh(CO)2Cl]2 and CpPt(Me)3 showed no reactivity at the platinum, though a possible modification of the mechanism of the [O]-Rh(CO)2Cl reaction with hydrogen was observed.
University of Southampton
Rudkin, Christopher Julian
1997
Rudkin, Christopher Julian
Rudkin, Christopher Julian
(1997)
Surface organometallic chemistry of rhodium and palladium on titania.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The combination of EXAFS and IR results has shown the adsorption of [Rh(CO)2Cl]2 onto titania to result in the formation of a discrete [O]-Rh(CO)2Cl species. Heating of the sample led to the formation of small metal particles at 433 K, with linearly bound CO shown as an intermediate by infrared studies. Further heating led to large, FCC like metal particles. Reaction of [O]-Rh(CO)2Cl with hydrogen will not proceed below 338 K at less than atmospheric pressure. No intermediate carbonyl species were detected for this reaction. Reaction with NO led to the loss of carbonyl coordination, which could be regenerated upon subsequent exposure to CO.
The adsorption of Rh(CO)2(acac), Rh(η3-C3H5)3, [Rh(C2H4)2Cl]2 and Rh(η5-C5H5)(CO)2 has also been investigated. Treatment of Rh(CO)2(acac) / TiO2 with hydrogen, or heating to 473 K leads to the formation of very small metal particles. A RhI(CO)2 species could be regenerated upon exposure to CO after initial reduction by hydrogen. The supported [Rh(C2H4)2Cl]2 species lost its dimeric structure upon reaction with the surface, but was still the least reactive of the rhodium systems, showing only some degree of clustering upon heating to 623 K.
Adsorption of Pd(allyl)cp onto titania results in the loss of allyl coordination. While heating to 573 K or exposure to CO produced large metal particles, reaction with H2 or NO caused only partial reduction of the sample.
A co-supported Rh/Pd system was prepared by simultaneous deposition of [Rh(CO)2Cl]2 and Pd(allyl)cp. This system showed 2 phases upon heating, one of small alloy like particles, the other of larger palladium rich particles, resulting from the Pd:Rh ratio of >1. A system prepared by sequential deposition of [Rh(CO)2Cl]2 and CpPt(Me)3 showed no reactivity at the platinum, though a possible modification of the mechanism of the [O]-Rh(CO)2Cl reaction with hydrogen was observed.
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Published date: 1997
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Local EPrints ID: 463052
URI: http://eprints.soton.ac.uk/id/eprint/463052
PURE UUID: 4f276210-96cc-459f-9578-ce1fa299a38a
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Date deposited: 04 Jul 2022 20:41
Last modified: 04 Jul 2022 20:41
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Author:
Christopher Julian Rudkin
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