C-H Activation in Diiron Bridging Vinyliminium Ligands: Reaction with CS2 to form New Zwitterionic Complexes acting as Organometallic Ligands

The reactions of vinyliminium complexes [Fe2{μ-η1:η3- C(R)=C(H)C=N(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (R = Xyl, R = Me, 1a; R = Xyl, R = Tol, 1b; R = Xyl, R = COOMe, 1c; R = Me, R = Me, 1d; R = Me, R = nBu, 1e; R = p-MeOC6H4, R = Me, 1f; Tol = 4-C6H4Me, Xyl = 2,6-Me2C6H3) with CS2 and NaH resulted in the replacement of CH hydrogen (in the bridging frame) with CS2 to give the corresponding dithiocarboxylate- vinyliminium complexes [Fe2{μ-η1:η3-C(R)=C- (CS2)C=N(Me)(R)}(μ-CO)(CO)(Cp)2] (2a–2f). Analogously, 1a and 1d reacted with NaH and SCNPh to afford the complexes [Fe2{μ-η1:η3-C(R)=C{C(NPh)S}C=N(Me)(R)}(μ-CO)(CO)(Cp)2] (R = Xyl, R = Me, 3a; R = Me, R = Me, 3b), respectively. Complex 2b was methylated at the dithiocarboxylate group Introduction Organic molecules acting as bridging ligands are expected to exhibit reaction patterns different to those observed when the same species are uncoordinated or are bound to a single metal centre.[1] An example is offered by the chemistry of the bridging vinyliminium diiron complexes I (Scheme 1).[2] Indeed, bridging vinyliminium ligands undergo nucleophilic addition at the iminium carbon or the adjacent α-carbon position[3] instead of the 1,4-conjugated addition normally observed in α,β-unsaturated iminium species.[4] Another unique feature of μ-vinyliminium ligands is the activation of α-C–H (C2–H in Scheme 1), which does not occur in uncoordinated conjugated iminium species.[5] The deprotonation of μ-vinyliminium ligands has been exploited to introduce a variety of substituents and functionalities into the bridging frame, as shown in Scheme 1. The carbon atoms in the bridging chain have been numbered as shown in Scheme 1 to make clearer the discussions presented hereafter. [a] Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Risorgimento 35, 56126 Pisa, Italy [b] Dipartimento di Chimica Fisica e Inorganica, Università di Bologna, Viale Risorgimento 4, 40136 Bologna, Italy E-mail: valerio.zanotti@unibo.it © 2011 Wiley-VCH Verlag 1260 GmbH & Co. KGaA, Weinheim Eur. J. Inorg. Chem. 2011, 1260–1268 upon treatment with CH3SO3CF3 to yield [Fe2{μ-η1:η3- C(R)=C(CS2Me)C=N(Me)(Xyl)}(μ-CO)(CO)(Cp)2][SO3CF3] (4a). Likewise, the zwitterionic complexes 2d–f underwent addition of the metal fragment [Fe(CO)2Cp]+ at the dithiocarboxylate group to yield the corresponding triiron complexes [Fe2{μ-η1:η3-C(R)=C(CS2Fp)C=N(Me)(R)}(μ-CO)(CO)(Cp)2]- [SO3CF3] [R = R = Me, 4b; R = Me, R = nBu, 4c; R = p- MeOC6H4, R = Me, 4d; Fp = Fe(CO)2Cp]. In a related reaction with [Pd(CH3CN)2Cl2], 2a binded to Pd through the dithiocarboxylate group as chelating ligand to afford the complex [PdCl2{κ2-(S,S)-2a}] (5). The X-ray structures of 2b, 3a and 4d have been determined.