Metallclusterverbindungen  Chemie und Bedeutung; Homogene und heterogene Katalyse

COMMUNICATIONS T = 25 "C, t = 3.5 h) also showed that complex 1 is able to perform more than 36 000 (yield 99.9 YO) without loss of activity.In order to rule out the participation in the catalysis of free, solvated [Rh(PPh,),]+ or similar cationic species formed by dissociation of complex 1, two independent experiments were made. First. the addition of four equivalents of Cs-2 did not alter the rate of reaction, which suggests that the common ion effect is absent. Second, hydrogenation experiments with added D,O provided further evidence to eliminate this hypothesis. If [Rh(PPh,),]+ or a related species were present, partially deuterated hexane would be found.["' By GC-MS analysis it was shown that the hexane formed in the reaction was not deuterium-enriched.The first e.w-monothiocarborane rhodium complex has been synthesized, and it catalyzed the hydrogenation of 1 -hexene eight times faster than Wilkinson's catalyst. The thioether group directly bonded to the cluster's open face enables discrimination between upper and lower belt B-H groups, leading to the formation of a B(l I)-H-Rh bond. This supports the initial hypothesis that the favoring of an exo-nido upper-belt form would readily enhance the hydrogenation activity of a rhodacarborane molecule. Experimental Procedure

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Große Übergangsmetallcluster, VIII. Wie verhalten sich trägergestützte Rh₅₅‐Cluster im Hydroformylierungsprozeß?

Schmid

Küpper

Hess

et al. 1991

Chem. Ber.

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Large Transition Metal Clusters, VIII. ‐ How Do Supported Rh55 Clusters Behave in the Hydroformylation Process? Two‐shell rhodium clusters of the type Rh55L12Clx [L = P(tBu)3, x = 20; L = PPh3, x = 6] can be anchored on TiO2 and Na‐ Y‐zeolite. High resolution transmission electron microscopy (HRTEM), BET, and DSC investigations prove that the clusters, about 20 Å in diameter, are fixed on the entrances of the micropores of the supports. The supported clusters catalyze the hydroformylation of ethene and propene variously. During the hydroformylation of ethene without a solvent or in aqueous suspension the catalyst is inactive after a few cycles. However, there is no loss of activity even after 27 experiments if propene is hydroformylated in an aqueous medium.

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Metallclusterverbindungen  Chemie und Bedeutung; Homogene und heterogene Katalyse

Cited by 14 publications

References 123 publications

Hydroformylierungskatalyse: In‐situ‐Charakterisierung eines zweikernigen Dihydridorhodium(II)‐Komplexes mit der bisher größten gemessenen Rh‐H‐NMR‐Kopplungskonstante

Hydroformylierungskatalyse: In‐situ‐Charakterisierung eines zweikernigen Dihydridorhodium(II)‐Komplexes mit der bisher größten gemessenen Rh‐H‐NMR‐Kopplungskonstante

Bimetallic Hydroformylation Catalysis: In Situ Characterization of a Dinuclear Rhodium(II) Dihydrido Complex with the Largest Rh–HNMR Coupling Constant

Große Übergangsmetallcluster, VIII. Wie verhalten sich trägergestützte Rh₅₅‐Cluster im Hydroformylierungsprozeß?

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Metallclusterverbindungen  Chemie und Bedeutung; Homogene und heterogene Katalyse

Cited by 14 publications

References 123 publications

Hydroformylierungskatalyse: In‐situ‐Charakterisierung eines zweikernigen Dihydridorhodium(II)‐Komplexes mit der bisher größten gemessenen Rh‐H‐NMR‐Kopplungskonstante

Hydroformylierungskatalyse: In‐situ‐Charakterisierung eines zweikernigen Dihydridorhodium(II)‐Komplexes mit der bisher größten gemessenen Rh‐H‐NMR‐Kopplungskonstante

Bimetallic Hydroformylation Catalysis: In Situ Characterization of a Dinuclear Rhodium(II) Dihydrido Complex with the Largest Rh–HNMR Coupling Constant

Große Übergangsmetallcluster, VIII. Wie verhalten sich trägergestützte Rh55‐Cluster im Hydroformylierungsprozeß?

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Große Übergangsmetallcluster, VIII. Wie verhalten sich trägergestützte Rh₅₅‐Cluster im Hydroformylierungsprozeß?