Synthesis and reactions of the novel sulfonium-methylidene complex [Fe2(CO)2(cp)2(μ-CO){μ-C(H) (SMe2)}]SO3CF3

The reaction of [Fe2(CO)2(cp)2(μ-CO){μ-C(H)(SMe)}] (cp=η-C5H5) with MeSO3CF3 forms the sulfonium-methylidene complex [Fe2(CO)2(cp)2(μ-CO){μ-C(H)(SMe2)}]SO3CF3 (3). Compared to Casey's methylidyne complex [Fe2(CO)2(cp)2 (μ- CO)(μ-CH)]PF6 (1), compound 3 appears to be more stable and easier to handle, still maintaining a reactivity centered at the μ-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(μ-CO){μ-C(H)(X)}]SO3CF3 (XNMe3, PMe3, PPh3, PHPh2) or neutral [Fe2(CO)2(cp)2(μ- CO){μ-C(H)(X)}] (XH-, MeO-, CN-) μ-methylidene derivatives, in good yield. The phosphonium complex [Fe2(CO)2(cp)2(μ- CO){μ-C(H)(PHPh2)}]SO3CF3 has been deprotonated with NEt3 to yield the novel phosphino-methylidene complex [Fe2(CO)2(cp)2(μ-CO){μ-C(H)(PPh2)}]. The presence of the SMe2 moiety in 3 reduces, compared to 1, the electrophilic character of the μ-C carbon, as evidenced by the reaction with styrene. © 1994.