SELECTIVE HOMOGENEOUS HYDROGENATIONS CATALYZED BY [(ETA-5-C5H5)FE(MU-3-CO)]4 .3.

The iron cluster, [(n5-C5H5)Fe(μ3-CO)]4, 1, catalyzes the selective hydrogenation of alkynes to alkenes at 100-130° and 100-1000 psig and the selective reduction of terminal alkynes to olefins in the presence of alkenes or internal alkynes. Internal alkynes are slowly reduced to cis olefins, aryl nitro groups to aniline derivatives, and terminal activated carbon-carbon double bonds (methyl acrylate, acrylonitrile) are hydrogenated. The cluster concentration, monitored by high pressure liquid chromatography, was unchanged after 1148 and 1410 turnovers. Cluster 1 was isolated in 95-97% yields after catalytic reduction (1000 turnovers) and no other iron-containing species were detected. After 280 turnovers, the catalyst solution was filtered through an ultrafiltration membrane into a second vessel where hydrogenation of 1-pentyne continued. Fragmentation of 1 tc. © 1979.