Unexpected reactions of (cyclooctatetraene) diiron hexacarbonyl with aryllithium reagents: Crystal structures of [(CO) 3Fe(1-4-η:5-7-η-C8H9)(CO) 2Fe(COC6H5)]

Article abstract of DOI:10.1016/S0022-328X(96)06815-5

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°C gave the (8,8-dihydro-1-4-η:5-7-η-cyclooctatrienyl)tricarbonylirondicarbonyl(arylfonnacyl)iron complexes [(CO)₃Fe(1-4-η:5-7-η-C₈H₉)(CO)₂Fe(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-η:5-8-η-cyclooctatetraene)tricarbonylirondicarbonyl[ethoxy(aryl)carbene]iron complexes [(CO)₃Fe(1-4-η:5-8-η-C₈H₈)(CO)₂FeC(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)₂Fe(COC₆H₅) moiety in 2a and the (CO)₂FeC(OC₂H₅)H₆H₅ moiety in 3a are on opposite sides of the cyclooctatetraene ring.