C-C bond formation through olefin-thiocarbyne coupling in diiron complexes |
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Authors: | Luigi Busetto Mauro Salmi Valerio Zanotti |
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Affiliation: | a Dipartimento di Chimica Fisica e Inorganica, Università di Bologna, Viale Risorgimento 4, 40136 Bologna, Italy b Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, I-56126 Pisa, Italy1Fabio Marchetti, born in 1974 in Bologna, Italy.1 |
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Abstract: | The bridging diiron thiocarbyne complex [Fe2{μ-CS(Me)}(μ-CO)(CO)2(Cp)2][SO3CF3] (1) reacts with activated olefins (methyl acrylate, acrylonitrile, styrene, diethyl maleate), in the presence of Me3NO and NaH, to give the corresponding μ-allylidene complexes [Fe2{μ-η1:η3-Cα(SMe)Cβ(R′)Cγ(H)(R″)} (μ-CO)(CO)(Cp)2] (R″ = CO2Me, R′ = H, 3a; R″ = CN, R′ = H, 3b; R″ = C6H5, R′ = H, 3c; R″ = R′ = CO2Et, 3d). The coupling reaction of olefin with thiocarbyne is regio- and stereospecific, leading to the formation of only one isomer. C-C bond formation occurs between the less substituted alkene carbon and the thiocarbyne. Moreover, olefinic hydrogens of the bridging ligands are mutually trans.The reactions of 3a-b with MeSO3CF3 result, selectively, in the formation of the cationic μ-sulphonium allylidene complexes [Fe2{μ-η1:η3-Cα(SMe2)Cβ (H)Cγ(H)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (R = CO2Me, 4a; R = CN, 4b). Compound 4a undergoes displacement of the SMe2 group by nucleophiles such as NaBH4, NBu4CN and NaOMe, affording the complexes [Fe2{μ-η1:η3-Cα(R)Cβ (H)Cγ(H)(CO2Me)}(μ-CO)(CO)(Cp)2] (R = H, 5a; R = CN, 5b; R = OMe, 5c), respectively. The molecular structures of 3a and 5a have been determined by X-ray diffraction studies. |
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Keywords: | Thiocarbyne Diiron complexes Allylidene Olefin insertion C-C bond formation |
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