SYNTHESIS AND REACTIONS OF THE NOVEL SULFONIUM-METHYLIDENE COMPLEX [FE2(CO)2(CP)2(MU-CO)(MU-C(H)(SME2))]SO3CF3

The reaction of [Fe2(CO)2(cp)2(mu-CO){mu-C(H)(SMe)}] (cp = eta5-C5H5) with MeSO3CF3 forms the sulfonium-methylidene complex [Fe2(CO)2(cp)2(mu-CO){mu-C(H)(SMe2)}]SO3CF3 (3). Compared to Casey's methylidyne complex [Fe2(CO)2(cp)2(mu-CO)(mu-CH)]PF6 (1), compound 3 appears to be more stable and easier to handle, still maintaining a reactivity centered at the mu-carbon. In fact 3 undergoes replacement of SMe2 by a variety of nucleophiles X, at room temperature, affording the corresponding cationic [Fe2(CO)2(cp)2(mu-CO){mu-C(H)(X)}]SO3CF3 (X = NMe3, PMe3, PPh3, PHPh2) or neutral [Fe2(CO)2(cp)2(mu-CO){mu-C(H)(X)}] (X = H-, MeO-, CN-) mu-methylidene derivatives, in good yield. The phosphonium complex [Fe2(CO)2(cp)2(mu-CO){mu-C(H)(PHPh2)}]SO3CF3 has been deprotonated with NEt3 to yield the novel phosphino-methylidene complex [Fe2(CO)2(cp)2(mu-CO){mu-C(H)(PPh2)}]. The presence of the SMe2 moiety in 3 reduces, compared to 1, the electrophilic character of the mu-C carbon, as evidenced by the reaction with styrene.