UNUSUAL REACTIONS OF PENTACARBONYL(CYCLOOCTATETRAENE)DIIRON WITH NUCLEOPHILES - SYNTHESIS AND STRUCTURE OF CYCLOOCTATETRAENE-COORDINATED DIIRON BRIDGING CARBENE COMPLEXES

The reaction of pentacarbonyl(cyclooctatetraene)diiron (1) with arylli thium reagents, ArLi (Ar = C6H5, o-, m-, and p-CH3C6H4, p-ClC6H4, p-CF 3C6H4), in ether at low temperature afforded acylmetalate intermediate s. Subsequent alkylation with Et3OBF4 in aqueous solution at 0-degrees -C gave the six new dimetal bridging carbene complexes C8H8(CO)2Fe{mu- C(OC2H5)Ar}Fe(CO)2 (2, Ar = C6H5; 3, Ar = o-CH3C6H4; 4, Ar = m-CH3C6H4 ; 5, Ar = p-CH3C6H4; 6, Ar = p-ClC6H4; 7, Ar = p-CF3C6H4); the structu re of 7 has been established by X-ray diffraction analysis. Complex 7 crystallized in the monoclinic system, space group P2(1)/n, with a = 8 .766(2) angstrom, b = 23.404(5) angstrom, c = 10.270(2) angstrom, beta = 94.25(2)degrees, V = 2101.27(7) angstrom3, Z = 4, D(calcd) = 1.68 g /cm3, R = 0.0347, and R(w) = 0.0330 for 2496 reflections with F(o)2 > 3sigma(F(o)2).