Novel ring-coupled reactions of bis(cycloheptatriene)tris(tricarbonyliron) with aryllithium reagents

Abstract

The reactions of the bis(cycloheptatriene)tris(tricarbonyliron), [(C₇H₈)₂{Fe(CO)₃}₃] 1, with aryllithium reagents RC₆H₄Li (R = H, o-, m-, p-CH₃, p-OCH₃), in diethyl ether at low temperature gave acylmetalate intermediates which following alkylation with Et₃OBF₄ in aqueous solution at 0 °C led to coupling of the two cycloheptatriene ligands to afford five novel isomerized (bicycloheptatriene)bis(tricarbonyliron)dicarbonyl[ethoxy(aryl)carbene]iron complexes [{(CO)₃Fe(C₇H₇)}₂(CO)₂FeC(OC₂H₅)C₆H₄R] (2, R = H; 3, R = o-CH₃; 4, R = m-CH₃; 5, R = p-CH₃; 6, R = p-OCH₃), of which the structure of 2 has been established by a single-crystal X-ray diffraction study. The reaction of complexes 2 or 5 with PPh₃ gave the chelated η³-allyliron phosphine adducts [{(CO)₃Fe(C₇H₇)}₂(CO)₂(PPh₃)FeC(OC₂H₅)C₆H₄R] (7, R = H; 8, R = p-CH₃).