The mu-sulfonium-methylidene diiron complexes [Fe-2{mu-C(X)SMe2}(mu-CO)(CO)(2)(Cp)(2)]SO3CF3 (X = CN, H) as precursors of mu-alkylidene complexes

The reactions of [Fe-2{mu-C(X)SMe2}(mu-CO)(CO)(2)(Cp)(2)]SO3CF3 (X = CN 2a, H 2b; Cp = eta-C5H5) with Li2Cu(CN)R-2 (R = Me, Bu-n, Ph, CCC6H4Me-4, C4H3 S) give the neutral mu-alkylidene complexes [Fe-2{mu-C(X)R}(mu-CO)(CO)(2)(C p)(2)] (3) arising from nucleophilic attack at the bridging carbon and SMe2 displacement. Likewise, 2a,b react with the sodium salt of dimethylmalonat e, diethylmalonate, ethylacetoacetate, 2,4-pentanedione, dibenzoylmethane a nd benzylcyanide, resulting in the formation of the corresponding functiona lized mu-alkylidene complexes [Fe-2{mu-C(X)R}(mu-CO)(CO)(2)(Cp)(2)] (5-7) ( X = CN, H; R = CH(COOMe)(2), CH(COOEt)(2), CH(COOMe)(COMe), CH(COMe)(2), CH (COPh)(2), CH(Ph)CN). The dichetone adducts [Fe-2{mu-C(X)CH(COR)(2)}(mu-CO) (CO)(2)(Cp)(2)] (X = CN, H; R = Me, Ph) undergo deacylation upon treatment with alumina, leading to the formation of the complexes [Fe-2{mu-C(X)CH2C(O )R}(mu-CO)(CO)(2)(Cp)(2)]. Reactions of 2a,b with LiBu or PhLi result in th e formation the metallacycles [Fe-2{mu-C(X)S(Me)CH2}(mu-CO)(CO)(CO)(Cp)(2)] (X = CN, 4a; H 4b) which arise from the deprotonation of an SMe group and the intramolecular addition at a terminally coordinated carbonyl. Finally, a comparison of the reactivity of 2a,b with that of the mu-carbyne diiron c omplexes [Fe-2(mu-CX)(mu-CO)(CO)(2)(Cp)(2)]SO3SF3 (X = H, SMe, NMe2) is pre sented. (C) 1999 Elsevier Science S.A. All rights reserved.