Unexpected reactions of (cyclooctatetraene) diiron hexacarbonyl with aryllithium reagents: Crystal structures of [(CO)(3)Fe(1-4-eta:5-7-eta-C8H9)(CO)(2)Fe(COC6H5)] and [(CO)(3)Fe(1-4-eta:5-8-eta-C8H8)(CO)(2)FeC(OC2H5)C6H5]

The reaction of (cyclooctatetraene)diiron hexacarbonyl (1) with aryllithium reagents ArLi (Ar = C6H5, o-, m-, p-CH3C6H4, p-CH3OC6H4) in ether at low temperature afforded acylmetalate intermediates. Subsequent alkylation with Et3OBF4 in aqueous solution at 0 degrees C gave the (8,8-dihydro-1-4-eta:5-7-eta-cyclooctatrienyl)tricarbonylirondicarbonyl(arylformacyl)iron complexes [(CO)(3)Fe(1-4-eta:5-7-eta-C8H9)(CO)(2)Fe(COAr)] (2a-e) (2a, Ar = C6H5; 2b, Ar = o-CH3C6H4; 2c, Ar = m-CH3C6H4; 2d, Ar = p-CH3C6H4; 2e, Ar = p-CH3OC6H4) and (1-4-eta:5-8-eta-cyclooctatetraene)tricarbonylirondicarbonyl [ethoxy(aryl)carbene]iron complexes [(CO)(3)Fe(1-4-eta:5-8-eta-C8H8)(CO)(2)FeC(OC2H5)Ar] (3a-e) (3a, Ar = C6H5; 3b, Ar = o-CH3C6H4; 3c, Ar = m-CH3C6H4; 3d, Ar = p-CH3C6H4; 3e, Ar = p-CH3OC6H4). The structures of 2a and 3a have been established by X-ray diffraction studies, which indicate that the Fe(CO)(3) unit and the (CO)(2)Fe(COC6H5) moiety in 2a and the (CO)(2)FeC(OC2H5)C6H5 moiety in 3a are on opposite sides of the cyclooctatetraene ring.