NEW SYNTHETIC METHOD FOR THE PREPARATION OF [(ETA-5-C5H5)FE(CO)(L)(UN)]BF4 (L=CO, PPH3, UN=UNSATURATED HYDROCARBON) COMPLEXES AND REDUCTION OF THE ETA-2-ACETYLENE COMPLEXES

The reaction of (η5-C5H5)Fe(CO)2I with AgBF4 in CH2Cl2 generates the reactive intermediate [(η5-C5H5)Fe(CO)2]+ in solution which, when mixed with 2 or 3 equivalents of an olefinic or acetylene ligand produces η2-olefin and η2-acetylene complexes in ca. 70% yield. The analogous reaction of (η5-C5H5)Fe(CO)(PPh3)I with AgBF4 in CH2Cl2 produces [(η5-C5H5)Fe(CO)(PPh3)]+ in solution which also reacts readily with olefins and acetylenes to yield new π-complexes. The dicarbonyl complexes are generally more stable than the phosphine-substituted complexes. The η2-acetylene complexes in both systems can be reduced with hydride reagents to yield the corresponding neutral σ-vinyl compounds. Although unstable in the dicarbonyl system, these vinyl compounds in the phosphine system are quite stable and show no tendency to isomerize or thermally decompose to a metal hydride as previously established for the analogous alkyl derivatives. Attempts to prepare cyano-substituted olefin complexes lead instead to new complexes in which the iron bonds to these ligands through the nitrogen lone-pair. © 1979.