Unexpected reactions of (cyclooctatetraene) diiron hexacarbonyl with aryllithium reagents: Crystal structures of [(CO) 3Fe(1–4-η:5–7-ηC 8H 9)(CO) 2Fe (COC 6H 5)] and [(CO) 3Fe(1–4-η:5–8-η-C 8 H 8)(CO) 2FeC(OC 2H 5)C 6H 5

Abstract

The reaction of (cyclooctatetraene)diiron hexacarbonyl ( 1) with aryllithium reagents ArLi (Ar = C 6H 5, o-, m-, p-CH 3C 6H 4, p-CH 3OC 6H 4 in ether at low temperature afforded acylmetalate intermediates. Subsequent alkylation with Et 3OBF 4 in aqueous solution at 0°C gave the (8,8-dihydro-1-4-η:5-7-η-cyclooctatrienyl) tricarbonylirondicarbonyl(arylformacyl)iron complexes [(CO) 3Fe(1–4-η:5–7-η-C 8H 9) (CO) 2Fe(COAr)] ( 2a-e) ( 2a, Ar = C 6H 5; 2b, Ar = o-CH 3C 6H 4; 2c, Ar = m-CH 3C 6H 4; 2d, Ar = p-CH 3C 6H 4; 2e, Ar = p-CH 3OC 6H 4) and (1–4-η:5–8-η-cyclooctatetraene)tricarbonylirondicarbonyl [ethoxy(aryl)carbene]iron complexes [(CO) 3Fe(1–4-η:5–8-η-C 8H 8) (CO) 2FeC(OC 2H 5)Ar] ( 3a-e) ( 3a, Ar = C 6H 5; 3b, Ar = o-CH 3C 6H 4; 3c, Ar = m-CH 3C 6H 4; 3d, Ar = p-CH 3C 6H 4; 3e, Ar = p-CH 3OC 6H 4). 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(COC 6H 5 moiety in 2a and the (CO) 2FeC(OC 2H 5)C 6H 5 moiety in 3a are on opposite sides of the cyclooctatetraene ring.