[Fec3(μ3-CR)(CO)10]− Cluster anions as building blocks for the synthesis of mixed-metal clusters: II. Synthesis of HFe3Rh(μ4-η2-CCHR)(CO)11 clusters (R = H or C6H5) and study of their catalytic activity (R = C6H5) under hydroformylation and hydrogenation conditions |
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Authors: | S Attali R Mathieu |
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Institution: | Laboratoire de Chimie de Coordination du CNRS, Unité no. 8241, liée par convention a l''Université Paul Sabatier, 205 route de Narbonne, 31400 Toulouse France |
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Abstract: | The mixed-metal vinylidene clusters HFe3Rh(CO)11(CCHR) (R = H, C6H5) have been synthesized via the reaction of HFe3(CO)3CCHR]P(C6H5)4] with RhCl(CO)2]2 in the presence of a thallium salt. The reaction initially gives the Fe3Rh(CO)11]CCHR]P(C6H5)4] cluster which leads to the final products by protonation. Spectroscopic data indicate a μ4-η2 mode of bonding for the vinylidene ligand. A structure with a Fe3Rh core in a butterfly configuration and in which the rhodium atom occupy a wing-tip site is proposed. The catalytic activity of HFe3Rh(CO)11(CCH(C6H5)) (80% yield) has been checked in hydroformylation and hydrogenation. In hydroformylation the cluster shows the same activity as Rh4(CO)12, whereas in hydrogenation the mixed-metal system shows specific activity; isomerization of 1-heptene to cis and trans 2-heptene takes place with no more than 14% heptane formation. The cluster is broken down during the catalysis, and some H3Fe3CO)9(μ3-CCH2(C6H5)) is formed. The latter cluster is not an active catalyst, and under the same conditions use of Rh4(CO)12 results mainly in hydrogenation of 1-heptene. These observations suggest that the active species is a mixed iron-rhodium system. |
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