Nanocluster catalyst lives longer

Nanocluster catalyst lives longerChinese chemists report a rhodium nanocluster catalyst that demonstrates "unprecedented" lifetime and activity in benzene hydrogenation under forcing conditions (J. Am. Chem. Soc. 2005, 127, 9694). The rhodium nanoclusters, which tend to coalesce into bulk metal on their own, are stabilized by the novel combination of a pyrrolidone-substituted, ionic-liquidlike copolymer (shown) dissolved in an imidazolium ionic liquid. The total turnovers for the catalyst--a measure of catalytic lifetime--exceeded 20,000 over five runs, which is more than five times the previous record for benzene hydrogenation by a nanocluster catalyst. Yuan Kou and coworkers at Peking University suggest that the high stability and activity of the rhodium catalyst are due to the combined stabilizing influences of the ionic liquid and the pyrrolidone-substituted copolymer. The stabilized rhodium nanoclusters, each roughly 3 nm across, were synthesized by hydrogenation of a mixture of RhCl3·3H2O and the copolymer dissolved in the ionic liquid.

Rhodium Nanoparticles Stabilized by Ionic Copolymers in Ionic Liquids : Long Lifetime Nanocluster Catalysts f

or Benzene Hydrogenation

Xin-dong Mu,† Jian-qiang Meng,‡ Zi-Chen Li,‡ and Yuan Kou*,†

J. Am. Chem. Soc. 2005, 127, 9694

H2

TTO (total turnovers):193000

[(n-C4H9)4N]5Na3[(1,5-COD)Rh•P2W15Nb3O62]

Aiken, J. D.; Finke, R. G. J. Am. Chem. Soc. 1999, 121, 8803-8810.

(a catalytic lifetime record for olefin hydrogenationby soluble nanoparticles)

TTO (total turnovers):2600

Widegren, J. A.; Finke, R. G. Inorg. Chem. 2002, 41, 1558-1572.

IrCl(cod)]2 (cod = 1,5-cyclooctadiene) / [BMI][PF6]

RhCl3 •3H2O / [BMI][PF6]

Pt2(dba)3 / [BMI][PF6]

[Ru(cod)(cot)] (cot=1,3,5-cyclooctatriene) / [BMI][PF6]

TTO= 3509 (32h)(a catalytic lifetime record for arene hydrogenationby soluble nanoparticles)

Fonseca, G. S.; Fonseca, A. P.; Teixeira, S. R.; Dupont, J. Chem.-Eur. J. 2003, 9, 3263-3269.

H2

4 atm

a zwitterionic imidazolium sulfonate-terminated thiol(zwitter-Au)

Tatumi, R.; Fujihara, H. Chem. Commun. 2005, 83-85.

Zhao, D.; Fei, Z.; Geldbach, T. J.; Scopelliti, R.; Dyson, P. J. J. Am.Chem. Soc. 2004, 126, 15876-15882.

Clement, N. D.; Cavell, K. J.; Jones, C.; Elsevier, C. J. Angew. Chem.,Int. Ed. 2004, 43, 1277-1279.

1,10-phenanthroline

Huang, J.; Jiang, T.; Han, B. X.; Gao, H. X.; Chang, Y. H.; Zhao, G. Y.; Wu, W. Z. Chem. Commun. 2003, 14, 1654-1655.

1-vinylimidazole

AIBN : azobisisobutyronitrile

NNC N CN

Soluble in BMIM ILs and MeOH

RX = bromoethane butylchloride

RhCl3•3H2O / copolymersdissolved in [BMI][BF4]

TTO

4000

phen

PVP

NO

* *n

.

Mercury poisoning experimentsThe ability of Hg(0) to poison metal-particle heterogeneous catalysts, by amalgamating the metal or adsorbing on the metal surface.

Conclsion

1. Containing imidazolium ionic liquidlike units have been synthesized. Rhodium nanoparticles stabilized by the ionic copolymer in ionic liquids have been successfully obtained.

2. The nanoparticles showed unprecedented lifetime and activity in arene hydrogenation under forcing conditions (a temperature of 75 °C and a hydrogen pressureof 40 bar) with a TTO of 20 000 (in five total recycles of 4000 TTOs each) and a TOF of 250 h-1, demonstrating that the combination of ionic liquids with ionic liquidlike stabilizers is a pathway towards highly stable and active nanoparticle catalysts.