Zwitterionic diiron vinyliminium complexes: Alkylation, metalation and oxidative coupling at the S and Se functionalities |
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Authors: | Luigi Busetto Fabio Marchetti Rita Mazzoni Stefano Zacchini |
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Institution: | a Dipartimento di Chimica Fisica e Inorganica, Università di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy b Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, I-56126 Pisa, Italy |
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Abstract: | The zwitterionic vinyliminium complex Fe2{μ-η1:η3-C(R′) C(S)C N(Me)(Xyl)}(μ-CO)(CO)(Cp)2] (2a) (R′ = p-Me-C6H4 (Tol), Xyl = 2,6-Me2C6H3) undergoes electrophilic addition at the S atom by HSO3CF3, MeSO3CF3, SiMe3Cl, BrCH2Ph, ICH2CH CH2 affording the complexes Fe2{μ-η1:η3-C(Tol) C(SX)C N(Me)(Xyl)}(μ-CO)(CO)(Cp)2]Y] (X = H, Y = SO3CF3, 4a; X = Me, Y = SO3CF3, 4b; X = SiMe3, Y = Cl, 4c; X = CH2Ph, Y = Br, 4d; X = CH2CH CH2, Y = I, 4e).Compound 2a and the corresponding vinyliminium complexes 2b and 2c (R′ = CH2OH, 2b; R′ = Me, 2c) react also with etherated BF3 leading to the formation of the corresponding S-adducts Fe2{μ-η1:η3-C(R′) C(SBF3)C N(Me)(Xyl)}(μ-CO)(CO)(Cp)2] (R′ = Tol, 5a; R′ = CH2OH, 5b; R′ = Me, 5c).In analogous reactions, the zwitterionic vinyliminium complexes undergo S-metalation upon treatment with in situ generated Fp]+SO3CF3]− Fp = Fe(CO)2(Cp)], leading to the formation of Fe2{μ-η1:η3-C(R′) C(S-Fp)C N(Me)(Xyl)}(μ-CO)(CO)(Cp)2]SO3CF3](R′ = CH2OH, 6a; R′ = Me, 6b; R′ = Bun, 6c).Similarly, zwitterionic vinyliminium containing Se in the place of S also undergo Se-electrophilic addition. Thus, the complexes Fe2{μ-η1:η3-C(R′) C(SeX)C N(Me)(R)}(μ-CO)(CO)(Cp)2]SO3CF3] (R = X = Me, R′ = Tol, 7a; R = Xyl, R′ = Me, X = Fp+, 7b) are obtained upon treatment of the neutral zwitterionic precursors with MeSO3CF3 and Fp]SO3CF3], respectively.Alkylation at the S or Se atom of the bridging ligand is also accomplished by CH2Cl2, used as solvent, although the reaction is slower compared to more efficient alkylating reagents. The complexes formed by this route are Fe2{μ-η1:η3-C(R′) C(E-CH2Cl)C N(Me)(R)}(μ-CO)(CO)(Cp)2]X] E = S, R = Xyl, R′ = Tol, X = Cl, 8a; E = S, R = Xyl, R′ = Me, X = Cl, 8b; E = Se, R = R′ = Me, X = BPh4, 8c].Finally, treatment of the zwitterionic vinyliminium complexes with I2 results in the oxidative coupling with formation of S-S (disulfide) or Se-Se (diselenide) bond. The reactions, performed in the presence of NaBPh4 afford the tetranuclear complexes Fe2{μ-η1:η3-C(R′) C(E)C N(Me)(R)}(μ-CO)(CO)(Cp)2]2BPh4]2 R = Xyl, R′ = CH2OH, E = S, 9a; R = Xyl, R′ = Me, E = S, 9b; R = Xyl, R′ = Bun, E = S, 9c; R = Xyl, R′ = Me, E = Se, 9d; R = Me, R′ = Bun, E = Se, 9e].The molecular structures of 4a, 8c and 9e have been determined by X-ray diffraction studies. |
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Keywords: | Vinyliminium Zwitterionic complexes Oxidative coupling Alkylation Disufides Diselenides |
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